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MySQL Connector/J 5.1 Developer Guide
Abstract
This manual describes how to install, configure, and develop
database applications using MySQL Connector/J, the JDBC
driver for communicating with MySQL servers.
For notes detailing the changes in each release of
Connector/J, see MySQL Connector/J Release Notes
(http://dev.mysql.com/doc/relnotes/connector-j/en/).
For legal information, see the Legal Notices.
For help with using MySQL, please visit either the MySQL
Forums (http://forums.mysql.com) or MySQL Mailing Lists
(http://lists.mysql.com), where you can discuss your issues
with other MySQL users.
For additional documentation on MySQL products, including
translations of the documentation into other languages, and
downloadable versions in variety of formats, including HTML
and PDF formats, see the MySQL Documentation Library
(http://dev.mysql.com/doc).
Licensing information. This product may include third-party
software, used under license. If you are using a Commercial
release of MySQL Connector/J 5.1, see this document
(http://downloads.mysql.com/docs/licenses/connector-j-5.1-com
-en.pdf) for licensing information, including licensing
information relating to third-party software that may be
included in this Commercial release. If you are using a
Community release of MySQL Connector/J 5.1, see this document
(http://downloads.mysql.com/docs/licenses/connector-j-5.1-gpl
-en.pdf) for licensing information, including licensing
information relating to third-party software that may be
included in this Community release.
Document generated on: 2016-03-28 (revision: 47177)
________________________________________________________
Preface and Legal Notices
This manual describes how to install, configure, and develop
database applications using MySQL Connector/J, the JDBC
driver for communicating with MySQL servers.
Legal Notices
Copyright (c) 1998, 2016, Oracle and/or its affiliates. All
rights reserved.
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Except as expressly permitted in your license agreement or
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means. Reverse engineering, disassembly, or decompilation of
this software, unless required by law for interoperability,
is prohibited.
The information contained herein is subject to change without
notice and is not warranted to be error-free. If you find any
errors, please report them to us in writing.
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affiliates reserve any and all rights to this documentation
not expressly granted above.
Chapter 1 Overview of MySQL Connector/J
MySQL provides connectivity for client applications developed
in the Java programming language with MySQL Connector/J, a
driver that implements the Java Database Connectivity (JDBC)
API
(http://www.oracle.com/technetwork/java/javase/jdbc/index.htm
l).
MySQL Connector/J is a JDBC Type 4 driver. Different versions
are available that are compatible with the JDBC 3.0 and JDBC
4.x specifications (see Chapter 2, "Connector/J Versions").
The Type 4 designation means that the driver is a pure Java
implementation of the MySQL protocol and does not rely on the
MySQL client libraries.
For large-scale programs that use common design patterns of
data access, consider using one of the popular persistence
frameworks such as Hibernate (http://www.hibernate.org/),
Spring's JDBC templates (http://www.springframework.org/) or
Ibatis SQL Maps (http://ibatis.apache.org/) to reduce the
amount of JDBC code for you to debug, tune, secure, and
maintain.
Key Topics
* For help with connection strings, connection options, and
setting up your connection through JDBC, see Section 5.1,
"Driver/Datasource Class Names, URL Syntax and
Configuration Properties for Connector/J."
Chapter 2 Connector/J Versions
There are currently four versions of MySQL Connector/J
available:
* Connector/J 5.1 is a Type 4 pure Java JDBC driver, which
conforms to the JDBC 3.0, 4.0, 4.1, and 4.2
specifications. It provides compatibility with all the
functionality of MySQL, including 4.1, 5.0, 5.1, 5.5,
5.6, and 5.7. Connector/J 5.1 provides ease of
development features, including auto-registration with
the Driver Manager, standardized validity checks,
categorized SQLExceptions, support for large update
counts, support for local and offset date-time variants
from the java.time package, support for JDBC-4.x XML
processing, support for per connection client
information, and support for the NCHAR
(http://dev.mysql.com/doc/refman/5.7/en/char.html),
NVARCHAR
(http://dev.mysql.com/doc/refman/5.7/en/char.html) and
NCLOB data types. This release also includes all bug
fixes up to and including Connector/J 5.0.6.
* Connector/J 5.0 provides support for all the
functionality offered by Connector/J 3.1 and includes
distributed transaction (XA) support.
* Connector/J 3.1 was designed for connectivity to MySQL
4.1 and MySQL 5.0 servers and provides support for all
the functionality in MySQL 5.0 except distributed
transaction (XA) support.
* Connector/J 3.0 provides core functionality and was
designed for connectivity to MySQL 3.x or MySQL 4.1
servers, although it provides basic compatibility with
later versions of MySQL. Connector/J 3.0 does not support
server-side prepared statements, and does not support any
of the features in versions of MySQL later than 4.1.
The following table summarizes the Connector/J versions
available, along with the details of JDBC driver type, what
version of the JDBC API it supports, what versions of MySQL
Server it works with, and whether it is currently supported
or not:
Table 2.1 Summary of Connector/J Versions
Connector/J version Driver Type JDBC version MySQL Server
version Status
5.1 4 3.0, 4.0, 4.1, 4.2 4.1, 5.0, 5.1, 5.5, 5.6, 5.7
Recommended version
5.0 4 3.0 4.1, 5.0 Released version
3.1 4 3.0 4.1, 5.0 Obsolete
3.0 4 3.0 3.x, 4.1 Obsolete
The current recommended version for Connector/J is 5.1. This
guide covers all four connector versions, with specific notes
given where a setting applies to a specific option.
2.1 Connector/J Release Notes and Change History
For details of new features and bug fixes in each Connector/J
release, see the MySQL Connector/J Release Notes
(http://dev.mysql.com/doc/relnotes/connector-j/en/).
2.2 Java Versions Supported
The following table summarizes what version of JRE is
required to use Connector/J with Java applications, and what
version of JDK is required to build Connector/J source code:
Table 2.2 Summary of Java Versions Required by Connector/J
Connector/J version JRE Supported JDK required (to build
source code)
5.1 1.5.x, 1.6.x, 1.7.x, 1.8.x 1.6.x and 1.5.x
5.0 1.3.x, 1.4.x, 1.5.x, 1.6.x 1.4.2, 1.5.x, 1.6.x
3.1 1.2.x, 1.3.x, 1.4.x, 1.5.x, 1.6.x 1.4.2, 1.5.x, 1.6.x
3.0 1.2.x, 1.3.x, 1.4.x, 1.5.x, 1.6.x 1.4.2, 1.5.x, 1.6.x
If you are building Connector/J from source code using the
source distribution (see Section 3.4, "Installing from
Source"), you must use JDK 1.4.2 or newer to compile the
package for Connector/J 5.0 or earlier. For Connector/J 5.1,
you must have both JDK-1.6.x AND JDK-1.5.x installed to be
able to build the source code.
JRE 1.7 support requires Connector/J 5.1.21 and higher.
JRE 1.8 is required for Connector/J 5.1 to connect to MySQL
5.6.27 and later and 5.7 with SSL/TLS when using some cipher
suites.
Several JDBC 4.1 methods were implemented for the first time
in Connector/J 5.1.21.
Because of the implementation of java.sql.Savepoint,
Connector/J 3.1.0 and newer will not run on a Java runtime
older than 1.4 unless the class verifier is turned off (by
setting the -Xverify:none option to the Java runtime). This
is because the class verifier will try to load the class
definition for java.sql.Savepoint even though it is not
accessed by the driver unless you actually use savepoint
functionality.
Caching functionality provided by Connector/J 3.1.0 or newer
is also not available on JVMs older than 1.4.x, as it relies
on java.util.LinkedHashMap, which was first available in
JDK-1.4.0.
MySQL Connector/J does not support JDK-1.1.x or JDK-1.0.x.
Chapter 3 Connector/J Installation
You can install the Connector/J package using either the
binary or source distribution. The binary distribution
provides the easiest method for installation; the source
distribution lets you customize your installation further.
With either solution, you manually add the Connector/J
location to your Java CLASSPATH.
If you are upgrading from a previous version, read the
upgrade information in Section 3.3, "Upgrading from an Older
Version" before continuing.
Connector/J is also available as part of the Maven project.
For more information and to download the Connector/J JAR
files, see the Maven repository
(http://search.maven.org/#search|ga|1|g%3A%22mysql%22%20AND%2
0a%3A%22mysql-connector-java%22).
3.1 Installing Connector/J from a Binary Distribution
For the easiest method of installation, use the binary
distribution of the Connector/J package. The binary
distribution is available either as a tar/gzip or zip file.
Extract it to a suitable location, then optionally make the
information about the package available by changing your
CLASSPATH (see Section 3.2, "Installing the Driver and
Configuring the CLASSPATH").
MySQL Connector/J is distributed as a .zip or .tar.gz archive
containing the sources, the class files, and the JAR archive
named mysql-connector-java-version-bin.jar.
Starting with Connector/J 3.1.9, the .class files that
constitute the JAR files are only included as part of the
driver JAR file.
Starting with Connector/J 3.1.8, the archive also includes a
debug build of the driver in a file named
mysql-connector-java-version-bin-g.jar. Do not use the debug
build of the driver unless instructed to do so when reporting
a problem or a bug, as it is not designed to be run in
production environments, and will have adverse performance
impact when used. The debug binary also depends on the
Aspect/J runtime library, which is located in the
src/lib/aspectjrt.jar file that comes with the Connector/J
distribution.
Use the appropriate graphical or command-line utility to
extract the distribution (for example, WinZip for the .zip
archive, and tar for the .tar.gz archive). Because there are
potentially long file names in the distribution, we use the
GNU tar archive format. Use GNU tar (or an application that
understands the GNU tar archive format) to unpack the .tar.gz
variant of the distribution.
3.2 Installing the Driver and Configuring the CLASSPATH
Once you have extracted the distribution archive, you can
install the driver by placing
mysql-connector-java-version-bin.jar in your classpath,
either by adding the full path to it to your CLASSPATH
environment variable, or by directly specifying it with the
command line switch -cp when starting the JVM.
To use the driver with the JDBC DriverManager, use
com.mysql.jdbc.Driver as the class that implements
java.sql.Driver.
You can set the CLASSPATH environment variable under Unix,
Linux, or OS X either locally for a user within their
.profile, .login or other login file. You can also set it
globally by editing the global /etc/profile file.
For example, add the Connector/J driver to your CLASSPATH
using one of the following forms, depending on your command
shell:
# Bourne-compatible shell (sh, ksh, bash, zsh):
shell> export CLASSPATH=/path/mysql-connector-java-ver-bin.jar:$CLASSP
ATH
# C shell (csh, tcsh):
shell> setenv CLASSPATH /path/mysql-connector-java-ver-bin.jar:$CLASSP
ATH
For Windows platforms, you set the environment variable
through the System Control Panel.
To use MySQL Connector/J with an application server such as
GlassFish, Tomcat, or JBoss, read your vendor's documentation
for more information on how to configure third-party class
libraries, as most application servers ignore the CLASSPATH
environment variable. For configuration examples for some
J2EE application servers, see Chapter 7, "Connection Pooling
with Connector/J," Section 8.2, "Configuring Load Balancing
with Connector/J," and Section 8.4, "Advanced Load-balancing
and Failover Configuration." However, the authoritative
source for JDBC connection pool configuration information for
your particular application server is the documentation for
that application server.
If you are developing servlets or JSPs, and your application
server is J2EE-compliant, you can put the driver's .jar file
in the WEB-INF/lib subdirectory of your webapp, as this is a
standard location for third party class libraries in J2EE web
applications.
You can also use the MysqlDataSource or
MysqlConnectionPoolDataSource classes in the
com.mysql.jdbc.jdbc2.optional package, if your J2EE
application server supports or requires them. Starting with
Connector/J 5.0.0, the javax.sql.XADataSource interface is
implemented using the
com.mysql.jdbc.jdbc2.optional.MysqlXADataSource class, which
supports XA distributed transactions when used in combination
with MySQL server version 5.0 and later.
The various MysqlDataSource classes support the following
parameters (through standard set mutators):
* user
* password
* serverName (see the previous section about failover
hosts)
* databaseName
* port
3.3 Upgrading from an Older Version
This section has information for users who are upgrading from
one version of Connector/J to another, or to a new version of
the MySQL server that supports a more recent level of JDBC. A
newer version of Connector/J might include changes to support
new features, improve existing functionality, or comply with
new standards.
3.3.1 Upgrading to MySQL Connector/J 5.1.x
* In Connector/J 5.0.x and earlier, the alias for a table
in a SELECT
(http://dev.mysql.com/doc/refman/5.7/en/select.html)
statement is returned when accessing the result set
metadata using ResultSetMetaData.getColumnName(). This
behavior however is not JDBC compliant, and in
Connector/J 5.1, this behavior has been changed so that
the original table name, rather than the alias, is
returned.
The JDBC-compliant behavior is designed to let API users
reconstruct the DML statement based on the metadata
within ResultSet and ResultSetMetaData.
You can get the alias for a column in a result set by
calling ResultSetMetaData.getColumnLabel(). To use the
old noncompliant behavior with
ResultSetMetaData.getColumnName(), use the
useOldAliasMetadataBehavior option and set the value to
true.
In Connector/J 5.0.x, the default value of
useOldAliasMetadataBehavior was true, but in Connector/J
5.1 this was changed to a default value of false.
3.3.2 JDBC-Specific Issues When Upgrading to MySQL Server 4.1 or
Newer
* Using the UTF-8 Character Encoding - Prior to MySQL
server version 4.1, the UTF-8 character encoding was not
supported by the server, however the JDBC driver could
use it, allowing storage of multiple character sets in
latin1 tables on the server.
Starting with MySQL-4.1, this functionality is
deprecated. If you have applications that rely on this
functionality, and can not upgrade them to use the
official Unicode character support in MySQL server
version 4.1 or newer, add the following property to your
connection URL:
useOldUTF8Behavior=true
* Server-side Prepared Statements - Connector/J 3.1 will
automatically detect and use server-side prepared
statements when they are available (MySQL server version
4.1.0 and newer). If your application encounters issues
with server-side prepared statements, you can revert to
the older client-side emulated prepared statement code
that is still presently used for MySQL servers older than
4.1.0 with the following connection property:
useServerPrepStmts=false
3.3.3 Upgrading from MySQL Connector/J 3.0 to 3.1
Connector/J 3.1 is designed to be backward-compatible with
Connector/J 3.0 as much as possible. Major changes are
isolated to new functionality exposed in MySQL-4.1 and newer,
which includes Unicode character sets, server-side prepared
statements, SQLState codes returned in error messages by the
server and various performance enhancements that can be
enabled or disabled using configuration properties.
* Unicode Character Sets: See the next section, as well as
Character Set Support
(http://dev.mysql.com/doc/refman/5.7/en/charset.html),
for information on this MySQL feature. If you have
something misconfigured, it will usually show up as an
error with a message similar to Illegal mix of
collations.
* Server-side Prepared Statements: Connector/J 3.1 will
automatically detect and use server-side prepared
statements when they are available (MySQL server version
4.1.0 and newer).
Starting with version 3.1.7, the driver scans SQL you are
preparing using all variants of
Connection.prepareStatement() to determine if it is a
supported type of statement to prepare on the server
side, and if it is not supported by the server, it
instead prepares it as a client-side emulated prepared
statement. You can disable this feature by passing
emulateUnsupportedPstmts=false in your JDBC URL.
If your application encounters issues with server-side
prepared statements, you can revert to the older
client-side emulated prepared statement code that is
still presently used for MySQL servers older than 4.1.0
with the connection property useServerPrepStmts=false.
* Datetimes with all-zero components (0000-00-00 ...):
These values cannot be represented reliably in Java.
Connector/J 3.0.x always converted them to NULL when
being read from a ResultSet.
Connector/J 3.1 throws an exception by default when these
values are encountered, as this is the most correct
behavior according to the JDBC and SQL standards. This
behavior can be modified using the zeroDateTimeBehavior
configuration property. The permissible values are:
+ exception (the default), which throws an
SQLException with an SQLState of S1009.
+ convertToNull, which returns NULL instead of the
date.
+ round, which rounds the date to the nearest closest
value which is 0001-01-01.
Starting with Connector/J 3.1.7, ResultSet.getString()
can be decoupled from this behavior using
noDatetimeStringSync=true (the default value is false) so
that you can retrieve the unaltered all-zero value as a
String. Note that this also precludes using any time zone
conversions, therefore the driver will not allow you to
enable noDatetimeStringSync and useTimezone at the same
time.
* New SQLState Codes: Connector/J 3.1 uses SQL:1999
SQLState codes returned by the MySQL server (if
supported), which are different from the legacy X/Open
state codes that Connector/J 3.0 uses. If connected to a
MySQL server older than MySQL-4.1.0 (the oldest version
to return SQLStates as part of the error code), the
driver will use a built-in mapping. You can revert to the
old mapping by using the configuration property
useSqlStateCodes=false.
* ResultSet.getString(): Calling ResultSet.getString() on a
BLOB (http://dev.mysql.com/doc/refman/5.7/en/blob.html)
column will now return the address of the byte[] array
that represents it, instead of a String representation of
the BLOB
(http://dev.mysql.com/doc/refman/5.7/en/blob.html). BLOB
(http://dev.mysql.com/doc/refman/5.7/en/blob.html) values
have no character set, so they cannot be converted to
java.lang.Strings without data loss or corruption.
To store strings in MySQL with LOB behavior, use one of
the TEXT
(http://dev.mysql.com/doc/refman/5.7/en/blob.html) types,
which the driver will treat as a java.sql.Clob.
* Debug builds: Starting with Connector/J 3.1.8 a debug
build of the driver in a file named
mysql-connector-java-version-bin-g.jar is shipped
alongside the normal binary jar file that is named
mysql-connector-java-version-bin.jar.
Starting with Connector/J 3.1.9, we do not ship the
.class files unbundled, they are only available in the
JAR archives that ship with the driver.
Do not use the debug build of the driver unless
instructed to do so when reporting a problem or bug, as
it is not designed to be run in production environments,
and will have adverse performance impact when used. The
debug binary also depends on the Aspect/J runtime
library, which is located in the src/lib/aspectjrt.jar
file that comes with the Connector/J distribution.
3.4 Installing from Source
Caution
To just get MySQL Connector/J up and running on your system,
install Connector/J using a standard binary release
distribution. Instructions in this section is only for users
who, for various reasons, want to compile Connector/J from
source.
The requirements and steps for installing from source
Connector/J 5.1.37 or later, 5.1.34 to 5.1.36, and 5.1.33 or
earlier are different; check the section below that is
relevant for the version you want.
Installing Connector/J 5.1.37 or later from source. To
install MySQL Connector/J from its source tree on GitHub, you
need to have the following software on your system:
* A Git client, to check out the sources from our GitHub
repository (available from http://git-scm.com/downloads).
* Apache Ant version 1.8.2 or newer (available from
http://ant.apache.org/).
* JDK 1.8.x AND JDK 1.5.x.
* JRE 1.6.x (optional)
* JUnit libraries (available from
https://github.com/junit-team/junit/wiki/Download-and-Ins
tall).
* The required .jar files from the Hibernate ORM 4.1 or 4.2
Final release bundle, which is available at
http://sourceforge.net/projects/hibernate/files/hibernate
4/.
To check out and compile MySQL Connector/J, follow these
steps:
1. Check out the code from the source code repository for
MySQL Connector/J located on GitHub at
https://github.com/mysql/mysql-connector-j; for the
latest release of the Connector/J 5.1 series, use the
following command:
shell> git clone https://github.com/mysql/mysql-connector-j.git
To check out a release other than the latest one, use the
--branch option to specify the revision tag for it:
shell> git clone --branch 5.1.xx https://github.com/mysql/mysql-connec
tor-j.git
Under the current directory, the commands create a
mysql-connector-j subdirectory , which contains the code
you want.
2. Make sure that you have both JDK 1.8.x AND JDK 1.5.x
installed. You need both JDKs because besides supporting
JDBC from 4.0 to 4.2, Connector/J 5.1 also supports JDBC
3.0, which is an older version and requires the older JDK
1.5.x.
3. Consider also having JRE 1.6.x installed. This is
optional: if JRE 1.6.x is not available or not supplied
to Ant with the property com.mysql.jdbc.java6.rtjar, the
Java 8 bootstrap classes will be used. A warning will be
returned, saying that the bootstrap class path was not
set with the option to compile sources written for Java
6.
4. Place the required junit.jar file in a separate
directory---for example, /home/username/ant-extralibs.
5. In the same directory for extra libraries described in
the last step, create a directory named hibernate4, and
put under it all the .jar files you can find under the
/lib/required/ folder in the Hibernate ORM 4 Final
release bundle.
6. Change your current working directory to the
mysql-connector-j directory created in step 1 above.
7. In the directory, create a file named build.properties to
indicate to Ant the locations of the root directories for
your JDK 1.8.x and JDK 1.5.x installations, the location
of the rt.jar of your JRE 1.6.x (optional), and the
location of the extra libraries. The file should contain
the following property settings, with the "path_to_*"
parts replaced by the appropriate filepaths:
com.mysql.jdbc.jdk8=path_to_jdk_1.8
com.mysql.jdbc.jdk5=path_to_jdk_1.5
com.mysql.jdbc.java6.rtjar=path_to_rt.jar_under_jre_1.6/rt.jar
com.mysql.jdbc.extra.libs=path_to_folder_for_extra_libraries
Alternatively, you can set the values of those properties
through the Ant -D options.
8. Issue the following command to compile the driver and
create a .jar file for Connector/J:
shell> ant dist
This creates a build directory in the current directory,
where all the build output goes. A directory is created
under the build directory, whose name includes the
version number of the release you are building. That
directory contains the sources, the compiled .class
files, and a .jar file for deployment. For more
information and other possible targets, including those
that create a fully packaged distribution, issue the
following command:
shell> ant -projecthelp
9. Install the newly created .jar file for the JDBC driver
as you would install a binary .jar file you download from
MySQL by following the instructions given in Section 3.2,
"Installing the Driver and Configuring the CLASSPATH."
Note that a package containing both the binary and source
code for Connector/J 5.1 can also be found at Connector/J 5.1
Download
(http://dev.mysql.com/downloads/connector/j/5.1.html).
Installing Connector/J 5.1.34 to 5.1.36 from source. To
install MySQL Connector/J 5.1.34 to 5.1.36 from the
Connector/J source tree on GitHub, make sure that you have
the following software on your system:
* A Git client, to check out the sources from our GitHub
repository (available from http://git-scm.com/downloads).
* Apache Ant version 1.8.2 or newer (available from
http://ant.apache.org/).
* JDK 1.6.x AND JDK 1.5.x.
* JUnit libraries (available from
https://github.com/junit-team/junit/wiki/Download-and-Ins
tall).
* The required .jar files from the Hibernate ORM 4.1 or 4.2
Final release bundle, which is available at
http://sourceforge.net/projects/hibernate/files/hibernate
4/.
To check out and compile MySQL Connector/J, follow these
steps:
1. Check out the code from the source code repository for
MySQL Connector/J located on GitHub at
https://github.com/mysql/mysql-connector-j, using the
--branch option to specify the revision tag for release
5.1.xx:
shell> git clone --branch 5.1.xx https://github.com/mysql/mysql-connec
tor-j.git
Under the current directory, the commands create a
mysql-connector-j subdirectory , which contains the code
you want.
2. Make sure that you have both JDK 1.6.x AND JDK 1.5.x
installed. You need both JDKs because Connector/J 5.1
supports both JDBC 3.0 (which has existed prior to JDK
1.6.x) and JDBC 4.0.
3. Place the required junit.jar file in a separate
directory---for example, /home/username/ant-extralibs.
4. In the same directory for extra libraries described in
the last step, create a directory named hibernate4, and
put under it all the .jar files you can find under the
/lib/required/ folder in the Hibernate ORM 4 Final
release bundle.
5. Change your current working directory to the
mysql-connector-j directory created in step 1 above.
6. In the directory, create a file named build.properties to
indicate to Ant the locations of the root directories for
your JDK 1.5.x and JDK 1.6.x installations, as well as
the location of the extra libraries. The file should
contain the following property settings, with the
"path_to_*" parts replaced by the appropriate filepaths:
com.mysql.jdbc.jdk5=path_to_jdk_1.5
com.mysql.jdbc.jdk6=path_to_jdk_1.6
com.mysql.jdbc.extra.libs=path_to_folder_for_extra_libraries
Alternatively, you can set the values of those properties
through the Ant -D options.
7. Issue the following command to compile the driver and
create a .jar file for Connector/J:
shell> ant dist
This creates a build directory in the current directory,
where all the build output goes. A directory is created
under the build directory, whose name includes the
version number of the release you are building. That
directory contains the sources, the compiled .class
files, and a .jar file for deployment. For more
information and other possible targets, including those
that create a fully packaged distribution, issue the
following command:
shell> ant -projecthelp
8. Install the newly created .jar file for the JDBC driver
as you would install a binary .jar file you download from
MySQL by following the instructions given in Section 3.2,
"Installing the Driver and Configuring the CLASSPATH."
Installing Connector/J 5.1.33 or earlier from the source
tree. To install MySQL Connector/J 5.1.33 or earlier from
the Connector/J source tree on GitHub, make sure that you
have the following software on your system:
* A Git client, to check out the source code from our
GitHub repository (available from
http://git-scm.com/downloads).
* Apache Ant version 1.7 or newer (available from
http://ant.apache.org/).
* JDK 1.6.x AND JDK 1.5.x. Refer to Section 2.2, "Java
Versions Supported" for the version of Java you need to
build or run any Connector/J release.
* The Ant Contrib (version 1.03b is available from
http://sourceforge.net/projects/ant-contrib/files/ant-con
trib/1.0b3/) and JUnit (available from
https://github.com/junit-team/junit/wiki/Download-and-Ins
tall) libraries.
* The required .jar files from the Hibernate ORM 4.1 or 4.2
Final release bundle, which is available at
http://sourceforge.net/projects/hibernate/files/hibernate
4/.
To check out and compile a specific branch of MySQL
Connector/J, follow these steps:
1. Check out the code from the source code repository for
MySQL Connector/J located on GitHub at
https://github.com/mysql/mysql-connector-j, using the
--branch option to specify the revision tag for release
5.1.xx:
shell> git clone --branch 5.1.xx https://github.com/mysql/mysql-connec
tor-j.git
Under the current directory, the commands create a
mysql-connector-j subdirectory , which contains the code
you want.
2. To build Connector/J 5.1, make sure that you have both
JDK 1.6.x AND JDK 1.5.x installed. You need both JDKs
because Connector/J 5.1 supports both JDBC 3.0 (which has
existed prior to JDK 1.6.x) and JDBC 4.0. Set your
JAVA_HOME environment variable to the path to the JDK
1.5.x installation.
3. Place the required ant-contrib.jar file (in exactly that
name, without the version number in it; rename the jar
file if needed) and junit.jar file in a separate
directory---for example, /home/username/ant-extralibs.
4. In the same directory for extra libraries described in
the last step, create a directory named hibernate4, and
put under it all the .jar files you can find under the
/lib/required/ folder in the Hibernate ORM 4 Final
release bundle.
5. Change your current working directory to the
mysql-connector-j directory created in step 1 above.
6. In the directory, create a file named build.properties to
indicate to Ant the locations of the Javac and rt.jar of
your JDK 1.6.x, as well as the location of the extra
libraries. The file should contain the following property
settings, with the "path_to_*" parts replaced by the
appropriate filepaths:
com.mysql.jdbc.java6.javac=path_to_javac_1.6/javac
com.mysql.jdbc.java6.rtjar=path_to_rt.jar_under_jdk_1.6/rt.jar
com.mysql.jdbc.extra.libs=path_to_folder_for_extra_libraries
Alternatively, you can set the values of those properties
through the Ant -D options.
7. Issue the following command to compile the driver and
create a .jar file for Connector/J:
shell> ant dist
This creates a build directory in the current directory,
where all the build output goes. A directory is created
under the build directory, whose name includes the
version number of the release you are building. That
directory contains the sources, the compiled .class
files, and a .jar file for deployment. For more
information and other possible targets, including those
that create a fully packaged distribution, issue the
following command:
shell> ant -projecthelp
8. Install the newly created .jar file for the JDBC driver
as you would install a binary .jar file you download from
MySQL by following the instructions given in Section 3.2,
"Installing the Driver and Configuring the CLASSPATH."
3.5 Testing Connector/J
The Connector/J source code repository or packages that are
shipped with source code include an extensive test suite,
containing test cases that can be executed independently. The
test cases are divided into the following categories:
* Functional or unit tests: Classes from the package
testsuite.simple. Include test code for the main features
of the Connector/J.
* Performance tests: Classes from the package
testsuite.perf. Include test code to make measurements
for the performance of Connector/J.
* Fabric tests: Classes from the package testsuite.fabric.
Includes the code to test Fabric-specific features. These
tests require the setting of some special properties that
are not documented here. Consult the code or the
Fabric-related targets in the bundled Ant build file,
build.xml.
* Regression tests: Classes from the package
testsuite.regression. Includes code for testing bug and
regression fixes.
The bundled Ant build file contains targets like test and
test-multijvm, which can facilitate the process of running
the Connector/J tests; see the target descriptions in the
build file for details. Besides the requirements for building
Connector/J from the source code described in Section 3.4,
"Installing from Source," a number of the tests also require
the File System Service Provider 1.2 for the Java Naming and
Directory Interface (JNDI), available at
http://www.oracle.com/technetwork/java/javasebusiness/downloa
ds/java-archive-downloads-java-plat-419418.html)---place the
jar files downloaded from there into the lib directory or in
the directory pointed to by the property
com.mysql.jdbc.extra.libs.
To run the test using Ant, in addition to the properties
required for Section 3.4, "Installing from Source," you must
set the following properties in the build.properties file or
through the Ant -D options:
* com.mysql.jdbc.testsuite.url: it specifies the JDBC URL
for connection to a MySQL test server; see Section 5.1,
"Driver/Datasource Class Names, URL Syntax and
Configuration Properties for Connector/J."
* com.mysql.jdbc.testsuite.jvm: the JVM to be used for the
tests. If the property is set, the specified JVM will be
used for all test cases except if it points to a Java 5
directory, in which case any test cases for JDBC 4.0 and
later are run with the JVM supplied with the property
com.mysql.jdbc.jdk8 (for 5.1.36 and earlier, supplied
with the property com.mysql.jdbc.jdk6). If the property
is not set, the JVM supplied with com.mysql.jdbc.jdk5
will be used to run test cases for JDBC 3.0 and the one
supplied with com.mysql.jdbc.jdk8 (for 5.1.36 and
earlier, supplied with the property com.mysql.jdbc.jdk6)
will be used to run test cases for JDBC 4.0 and later.
After setting these parameters, run the tests with Ant in the
following ways:
* Building the test target with ant test runs all test
cases by default on a single server instance. If you want
to run a particular test case, put the test's fully
qualified class names in the test variable; for example:
shell > ant -Dtest=testsuite.simple.StringUtilsTest test
You can also run individual tests in a test case by
specifying the names of the corresponding methods in the
methods variable, separating multiple methods by commas;
for example:
shell > ant -Dtest=testsuite.simple.StringUtilsTest -Dmethods=testInde
xOfIgnoreCase,testGetBytes test
* Building the test-multijvm target with ant test-multijvm
runs all the test cases using multiple JVMs of different
versions on multiple server instances. For example, if
you want to run the tests using a Java 7 and a Java 8 JVM
on three server instances with different configurations,
you will need to use the following properties:
com.mysql.jdbc.testsuite.jvm.1=path_to_Java_7
com.mysql.jdbc.testsuite.jvm.2=path_to_Java_8
com.mysql.jdbc.testsuite.url.1=URL_to_1st_server
com.mysql.jdbc.testsuite.url.2=URL_to_2nd_server
com.mysql.jdbc.testsuite.url.3=URL_to_3rd_server
Unlike the target test, the target test-multijvm only
recognizes the properties com.mysql.jdbc.testsuite.jvm.N
and com.mysql.jdbc.testsuite.url.N, where N is a numeric
suffice; the same properties without the suffices are
ignored by test-multijvm. As with the target test, if any
of the com.mysql.jdbc.testsuite.jvm.N settings points to
Java 5, then Ant relies on the property
com.mysql.jdbc.jdk8 to run the tests specific to JDBC 4.0
and later.
You can choose to run individual test cases or specific
tests by using the test or methods property, as explained
in the last bullet for the target test. Each test is run
once per possible combination of JVMs and server
instances (that is, 6 times in total for in this
example).
When a test for a certain JVM-server combination has
failed, test-multijvm does not throw an error, but moves
on to the next combination, until all tests for all
combinations are finished.
While the test results are partially reported by the console,
complete reports in HTML and XML formats are provided:
* For results of test: view the HTML report by opening
build/junit/unitregress/report/index.html. XML version of
the reports are located in the folder
build/junit/unitregress.
* For results of test-multijvm: view the HTML report for
each JVM-server combination by opening
build/junit/MySQLN.server_version/operating_system_versio
n/jvm-version/unitregress/report/index.html. XML version
of the reports are located in the folder
build/junit/MySQLN.server_version/operating_system_versio
n/jvm-version/unitregress.
Chapter 4 Connector/J Examples
Examples of using Connector/J are located throughout this
document. This section provides a summary and links to these
examples.
* Example 6.1, "Connector/J: Obtaining a connection from
the DriverManager"
* Example 6.2, "Connector/J: Using java.sql.Statement to
execute a SELECT query"
* Example 6.3, "Connector/J: Calling Stored Procedures"
* Example 6.3, "Connector/J: Using
Connection.prepareCall()"
* Example 6.3, "Connector/J: Registering output parameters"
* Example 6.3, "Connector/J: Setting CallableStatement
input parameters"
* Example 6.3, "Connector/J: Retrieving results and output
parameter values"
* Example 6.4, "Connector/J: Retrieving AUTO_INCREMENT
column values using Statement.getGeneratedKeys()"
* Example 6.4, "Connector/J: Retrieving AUTO_INCREMENT
column values using SELECT LAST_INSERT_ID()"
* Example 6.4, "Connector/J: Retrieving AUTO_INCREMENT
column values in Updatable ResultSets"
* Example 7, "Connector/J: Using a connection pool with a
J2EE application server"
* Example 15, "Connector/J: Example of transaction with
retry logic"
Chapter 5 Connector/J (JDBC) Reference
This section of the manual contains reference material for
MySQL Connector/J.
5.1 Driver/Datasource Class Names, URL Syntax and Configuration
Properties for Connector/J
The name of the class that implements java.sql.Driver in
MySQL Connector/J is com.mysql.jdbc.Driver. The
org.gjt.mm.mysql.Driver class name is also usable for
backward compatibility with MM.MySQL, the predecessor of
Connector/J. Use this class name when registering the driver,
or when configuring a software to use MySQL Connector/J.
JDBC URL Format
The general format for a JDBC URL for connecting to a MySQL
server is as follows, with items in square brackets ([ ])
being optional:
jdbc:mysql://[host1][:port1][,[host2][:port2]]...[/[database]] ??
[?propertyName1=propertyValue1[&propertyName2=propertyValue2]...]
Here is a simple example for a connection URL:
jdbc:mysql://localhost:3306/sakila?profileSQL=true
Supply multiple hosts for a server failover setup (see
Chapter 8, "Multi-Host Connections" for details):
# Connection URL for a server failover setup:
jdbc:mysql//primaryhost,secondaryhost1,secondaryhost2/test
There are specialized URL schemes for configuring
Connector/J's multi-host functions like load balancing and
replication; here are some examples (see Chapter 8,
"Multi-Host Connections" for details):
# Connection URL for load balancing:
jdbc:mysql:loadbalance://localhost:3306,localhost:3310/sakila
# Connection URL for server replication:
jdbc:mysql:replication://master,slave1,slave2,slave3/test
Host and Port
If no hosts are not specified, the host name defaults to
127.0.0.1. If the port for a host is not specified, it
defaults to 3306, the default port number for MySQL servers.
Initial Database for Connection
If the database is not specified, the connection is made with
no default database. In this case, either call the
setCatalog() method on the Connection instance, or fully
specify table names using the database name (that is, SELECT
dbname.tablename.colname FROM dbname.tablename...) in your
SQL. Opening a connection without specifying the database to
use is generally only useful when building tools that work
with multiple databases, such as GUI database managers.
Note
Always use the Connection.setCatalog() method to specify the
desired database in JDBC applications, rather than the USE
database statement.
IPv6 Connections
For IPv6 connections, use this alternative syntax to specify
hosts in the URL (the same syntax can also be used for IPv4
connections):
jdbc:mysql://address=(key1=value)[(key2=value)]...[,address=(key3=valu
e)[(key4=value)]...]...[/[database]]??
[?propertyName1=propertyValue1[&propertyName2=propertyValue2]...]
Supported keys include:
* (protocol=tcp), or (protocol=pipe) for named pipes on
Windows.
* (path=path_to_pipe) for named pipes.
* (host=hostname) for TCP connections.
* (port=port_number) for TCP connections.
For example:
jdbc:mysql://address=(protocol=tcp)(host=localhost)(port=3306)/db
Keys other than the four mentioned above are treated as
host-specific configuration properties, which allow per-host
overrides of any configuration property set for multi-host
connections (that is, when using failover, load balancing, or
replication). For example:
# IPv6 Connection URL for a server failover setup:
jdbc:mysql//address=(protocol=tcp)(host=primaryhost)(port=3306),??
address=(protocol=tcp)(host=secondaryhost1)(port=3310)(user=test2)/tes
t
# IPv6 Connection URL for load balancing:
jdbc:mysql:loadbalance://address=(protocol=tcp)(host=localhost)(port=3
306)(user=test1),??
address=(protocol=tcp)(host=localhost)(port=3310)(user=test2)/sakila
# IPv6 Connection URL for server replication:
jdbc:mysql:replication://address=(protocol=tcp)(host=master)(port=3306
)(user=test1),??
address=(protocol=tcp)(host=slave1)(port=3310)(user=test2)/test
Limit the overrides to user, password, network timeouts, and
statement and metadata cache sizes; the effects of other
per-host overrides are not defined.
The ways to set the other configuration properties are the
same for IPv6 and IPv4 URLs; see Section 5.1, "."
Setting Configuration Properties
Configuration properties define how Connector/J will make a
connection to a MySQL server. Unless otherwise noted,
properties can be set for a DataSource object or for a
Connection object.
Configuration properties can be set in one of the following
ways:
* Using the set*() methods on MySQL implementations of
java.sql.DataSource (which is the preferred method when
using implementations of java.sql.DataSource):
+ com.mysql.jdbc.jdbc2.optional.MysqlDataSource
+ com.mysql.jdbc.jdbc2.optional.MysqlConnectionPoolDat
aSource
* As a key/value pair in the java.util.Properties instance
passed to DriverManager.getConnection() or
Driver.connect()
* As a JDBC URL parameter in the URL given to
java.sql.DriverManager.getConnection(),
java.sql.Driver.connect() or the MySQL implementations of
the javax.sql.DataSource setURL() method. If you specify
a configuration property in the URL without providing a
value for it, nothing will be set; for example, adding
useServerPrepStmts alone to the URL does not make
Connector/J use server-side prepared statements; you need
to add useServerPrepStmts=true.
Note
If the mechanism you use to configure a JDBC URL is
XML-based, use the XML character literal & to
separate configuration parameters, as the ampersand is a
reserved character for XML.
The properties are listed in the following tables.
Connection/Authentication.
Properties and Descriptions
user
The user to connect as
Since version: all versions
password
The password to use when connecting
Since version: all versions
socketFactory
The name of the class that the driver should use for creating
socket connections to the server. This class must implement
the interface 'com.mysql.jdbc.SocketFactory' and have public
no-args constructor.
Default: com.mysql.jdbc.StandardSocketFactory
Since version: 3.0.3
connectTimeout
Timeout for socket connect (in milliseconds), with 0 being no
timeout. Only works on JDK-1.4 or newer. Defaults to '0'.
Default: 0
Since version: 3.0.1
socketTimeout
Timeout on network socket operations (0, the default means no
timeout).
Default: 0
Since version: 3.0.1
connectionLifecycleInterceptors
A comma-delimited list of classes that implement
"com.mysql.jdbc.ConnectionLifecycleInterceptor" that should
notified of connection lifecycle events (creation,
destruction, commit, rollback, setCatalog and setAutoCommit)
and potentially alter the execution of these commands.
ConnectionLifecycleInterceptors are "stackable", more than
one interceptor may be specified via the configuration
property as a comma-delimited list, with the interceptors
executed in order from left to right.
Since version: 5.1.4
useConfigs
Load the comma-delimited list of configuration properties
before parsing the URL or applying user-specified properties.
These configurations are explained in the 'Configurations' of
the documentation.
Since version: 3.1.5
authenticationPlugins
Comma-delimited list of classes that implement
com.mysql.jdbc.AuthenticationPlugin and which will be used
for authentication unless disabled by
"disabledAuthenticationPlugins" property.
Since version: 5.1.19
defaultAuthenticationPlugin
Name of a class implementing
com.mysql.jdbc.AuthenticationPlugin which will be used as the
default authentication plugin (see below). It is an error to
use a class which is not listed in "authenticationPlugins"
nor it is one of the built-in plugins. It is an error to set
as default a plugin which was disabled with
"disabledAuthenticationPlugins" property. It is an error to
set this value to null or the empty string (i.e. there must
be at least a valid default authentication plugin specified
for the connection, meeting all constraints listed above).
Default:
com.mysql.jdbc.authentication.MysqlNativePasswordPlugin
Since version: 5.1.19
disabledAuthenticationPlugins
Comma-delimited list of classes implementing
com.mysql.jdbc.AuthenticationPlugin or mechanisms, i.e.
"mysql_native_password". The authentication plugins or
mechanisms listed will not be used for authentication which
will fail if it requires one of them. It is an error to
disable the default authentication plugin (either the one
named by "defaultAuthenticationPlugin" property or the
hard-coded one if "defaultAuthenticationPlugin" property is
not set).
Since version: 5.1.19
disconnectOnExpiredPasswords
If "disconnectOnExpiredPasswords" is set to "false" and
password is expired then server enters "sandbox" mode and
sends ERR(08001, ER_MUST_CHANGE_PASSWORD) for all commands
that are not needed to set a new password until a new
password is set.
Default: true
Since version: 5.1.23
interactiveClient
Set the CLIENT_INTERACTIVE flag, which tells MySQL to timeout
connections based on INTERACTIVE_TIMEOUT instead of
WAIT_TIMEOUT
Default: false
Since version: 3.1.0
localSocketAddress
Hostname or IP address given to explicitly configure the
interface that the driver will bind the client side of the
TCP/IP connection to when connecting.
Since version: 5.0.5
propertiesTransform
An implementation of
com.mysql.jdbc.ConnectionPropertiesTransform that the driver
will use to modify URL properties passed to the driver before
attempting a connection
Since version: 3.1.4
useCompression
Use zlib compression when communicating with the server
(true/false)? Defaults to 'false'.
Default: false
Since version: 3.0.17
Networking.
Properties and Descriptions
socksProxyHost
Name or IP address of SOCKS host to connect through.
Since version: 5.1.34
socksProxyPort
Port of SOCKS server.
Default: 1080
Since version: 5.1.34
maxAllowedPacket
Maximum allowed packet size to send to server. If not set,
the value of system variable 'max_allowed_packet' will be
used to initialize this upon connecting. This value will not
take effect if set larger than the value of
'max_allowed_packet'. Also, due to an internal dependency
with the property "blobSendChunkSize", this setting has a
minimum value of "8203" if "useServerPrepStmts" is set to
"true".
Default: -1
Since version: 5.1.8
tcpKeepAlive
If connecting using TCP/IP, should the driver set
SO_KEEPALIVE?
Default: true
Since version: 5.0.7
tcpNoDelay
If connecting using TCP/IP, should the driver set
SO_TCP_NODELAY (disabling the Nagle Algorithm)?
Default: true
Since version: 5.0.7
tcpRcvBuf
If connecting using TCP/IP, should the driver set SO_RCV_BUF
to the given value? The default value of '0', means use the
platform default value for this property)
Default: 0
Since version: 5.0.7
tcpSndBuf
If connecting using TCP/IP, should the driver set SO_SND_BUF
to the given value? The default value of '0', means use the
platform default value for this property)
Default: 0
Since version: 5.0.7
tcpTrafficClass
If connecting using TCP/IP, should the driver set traffic
class or type-of-service fields ?See the documentation for
java.net.Socket.setTrafficClass() for more information.
Default: 0
Since version: 5.0.7
High Availability and Clustering.
Properties and Descriptions
autoReconnect
Should the driver try to re-establish stale and/or dead
connections? If enabled the driver will throw an exception
for a queries issued on a stale or dead connection, which
belong to the current transaction, but will attempt reconnect
before the next query issued on the connection in a new
transaction. The use of this feature is not recommended,
because it has side effects related to session state and data
consistency when applications don't handle SQLExceptions
properly, and is only designed to be used when you are unable
to configure your application to handle SQLExceptions
resulting from dead and stale connections properly.
Alternatively, as a last option, investigate setting the
MySQL server variable "wait_timeout" to a high value, rather
than the default of 8 hours.
Default: false
Since version: 1.1
autoReconnectForPools
Use a reconnection strategy appropriate for connection pools
(defaults to 'false')
Default: false
Since version: 3.1.3
failOverReadOnly
When failing over in autoReconnect mode, should the
connection be set to 'read-only'?
Default: true
Since version: 3.0.12
maxReconnects
Maximum number of reconnects to attempt if autoReconnect is
true, default is '3'.
Default: 3
Since version: 1.1
reconnectAtTxEnd
If autoReconnect is set to true, should the driver attempt
reconnections at the end of every transaction?
Default: false
Since version: 3.0.10
retriesAllDown
When using loadbalancing or failover, the number of times the
driver should cycle through available hosts, attempting to
connect. Between cycles, the driver will pause for 250ms if
no servers are available.
Default: 120
Since version: 5.1.6
initialTimeout
If autoReconnect is enabled, the initial time to wait between
re-connect attempts (in seconds, defaults to '2').
Default: 2
Since version: 1.1
roundRobinLoadBalance
When autoReconnect is enabled, and failoverReadonly is false,
should we pick hosts to connect to on a round-robin basis?
Default: false
Since version: 3.1.2
queriesBeforeRetryMaster
Number of queries to issue before falling back to the primary
host when failed over (when using multi-host failover).
Whichever condition is met first, 'queriesBeforeRetryMaster'
or 'secondsBeforeRetryMaster' will cause an attempt to be
made to reconnect to the primary host. Setting both
properties to 0 disables the automatic fall back to the
primary host at transaction boundaries. Defaults to 50.
Default: 50
Since version: 3.0.2
secondsBeforeRetryMaster
How long should the driver wait, when failed over, before
attempting to reconnect to the primary host? Whichever
condition is met first, 'queriesBeforeRetryMaster' or
'secondsBeforeRetryMaster' will cause an attempt to be made
to reconnect to the master. Setting both properties to 0
disables the automatic fall back to the primary host at
transaction boundaries. Time in seconds, defaults to 30
Default: 30
Since version: 3.0.2
allowMasterDownConnections
By default, a replication-aware connection will fail to
connect when configured master hosts are all unavailable at
initial connection. Setting this property to 'true' allows to
establish the initial connection, by failing over to the
slave servers, in read-only state. It won't prevent
subsequent failures when switching back to the master hosts
i.e. by setting the replication connection to read/write
state.
Default: false
Since version: 5.1.27
allowSlaveDownConnections
By default, a replication-aware connection will fail to
connect when configured slave hosts are all unavailable at
initial connection. Setting this property to 'true' allows to
establish the initial connection. It won't prevent failures
when switching to slaves i.e. by setting the replication
connection to read-only state. The property
'readFromMasterWhenNoSlaves' should be used for this purpose.
Default: false
Since version: 5.1.38
readFromMasterWhenNoSlaves
Replication-aware connections distribute load by using the
master hosts when in read/write state and by using the slave
hosts when in read-only state. If, when setting the
connection to read-only state, none of the slave hosts are
available, an SQLExeception is thrown back. Setting this
property to 'true' allows to fail over to the master hosts,
while setting the connection state to read-only, when no
slave hosts are available at switch instant.
Default: false
Since version: 5.1.38
replicationEnableJMX
Enables JMX-based management of load-balanced connection
groups, including live addition/removal of hosts from
load-balancing pool.
Default: false
Since version: 5.1.27
selfDestructOnPingMaxOperations
=If set to a non-zero value, the driver will report close the
connection and report failure when Connection.ping() or
Connection.isValid(int) is called if the connection's count
of commands sent to the server exceeds this value.
Default: 0
Since version: 5.1.6
selfDestructOnPingSecondsLifetime
If set to a non-zero value, the driver will report close the
connection and report failure when Connection.ping() or
Connection.isValid(int) is called if the connection's
lifetime exceeds this value.
Default: 0
Since version: 5.1.6
resourceId
A globally unique name that identifies the resource that this
datasource or connection is connected to, used for
XAResource.isSameRM() when the driver can't determine this
value based on hostnames used in the URL
Since version: 5.0.1
Security.
Properties and Descriptions
allowMultiQueries
Allow the use of ';' to delimit multiple queries during one
statement (true/false), defaults to 'false', and does not
affect the addBatch() and executeBatch() methods, which
instead rely on rewriteBatchStatements.
Default: false
Since version: 3.1.1
useSSL
Use SSL when communicating with the server (true/false),
default is 'true' when connecting to MySQL 5.5.45+, 5.6.26+
or 5.7.6+, otherwise default is 'false'
Default: false
Since version: 3.0.2
requireSSL
Require server support of SSL connection if useSSL=true?
(defaults to 'false').
Default: false
Since version: 3.1.0
verifyServerCertificate
If "useSSL" is set to "true", should the driver verify the
server's certificate? When using this feature, the keystore
parameters should be specified by the
"clientCertificateKeyStore*" properties, rather than system
properties. Default is 'false' when connecting to MySQL
5.5.45+, 5.6.26+ or 5.7.6+ and "useSSL" was not explicitly
set to "true". Otherwise default is 'true'
Default: true
Since version: 5.1.6
clientCertificateKeyStoreUrl
URL to the client certificate KeyStore (if not specified, use
defaults)
Since version: 5.1.0
clientCertificateKeyStoreType
KeyStore type for client certificates (NULL or empty means
use the default, which is "JKS". Standard keystore types
supported by the JVM are "JKS" and "PKCS12", your environment
may have more available depending on what security products
are installed and available to the JVM.
Default: JKS
Since version: 5.1.0
clientCertificateKeyStorePassword
Password for the client certificates KeyStore
Since version: 5.1.0
trustCertificateKeyStoreUrl
URL to the trusted root certificate KeyStore (if not
specified, use defaults)
Since version: 5.1.0
trustCertificateKeyStoreType
KeyStore type for trusted root certificates (NULL or empty
means use the default, which is "JKS". Standard keystore
types supported by the JVM are "JKS" and "PKCS12", your
environment may have more available depending on what
security products are installed and available to the JVM.
Default: JKS
Since version: 5.1.0
trustCertificateKeyStorePassword
Password for the trusted root certificates KeyStore
Since version: 5.1.0
enabledSSLCipherSuites
If "useSSL" is set to "true", overrides the cipher suites
enabled for use on the underlying SSL sockets. This may be
required when using external JSSE providers or to specify
cipher suites compatible with both MySQL server and used JVM.
Since version: 5.1.35
allowLoadLocalInfile
Should the driver allow use of 'LOAD DATA LOCAL INFILE...'
(defaults to 'true').
Default: true
Since version: 3.0.3
allowUrlInLocalInfile
Should the driver allow URLs in 'LOAD DATA LOCAL INFILE'
statements?
Default: false
Since version: 3.1.4
allowPublicKeyRetrieval
Allows special handshake roundtrip to get server RSA public
key directly from server.
Default: false
Since version: 5.1.31
paranoid
Take measures to prevent exposure sensitive information in
error messages and clear data structures holding sensitive
data when possible? (defaults to 'false')
Default: false
Since version: 3.0.1
passwordCharacterEncoding
What character encoding is used for passwords? Leaving this
set to the default value (null), uses the value set in
"characterEncoding" if there is one, otherwise uses UTF-8 as
default encoding. If the password contains non-ASCII
characters, the password encoding must match what server
encoding was set to when the password was created. For
passwords in other character encodings, the encoding will
have to be specified with this property (or with
"characterEncoding"), as it's not possible for the driver to
auto-detect this.
Since version: 5.1.7
serverRSAPublicKeyFile
File path to the server RSA public key file for
sha256_password authentication. If not specified, the public
key will be retrieved from the server.
Since version: 5.1.31
Performance Extensions.
Properties and Descriptions
callableStmtCacheSize
If 'cacheCallableStmts' is enabled, how many callable
statements should be cached?
Default: 100
Since version: 3.1.2
metadataCacheSize
The number of queries to cache ResultSetMetadata for if
cacheResultSetMetaData is set to 'true' (default 50)
Default: 50
Since version: 3.1.1
useLocalSessionState
Should the driver refer to the internal values of autocommit
and transaction isolation that are set by
Connection.setAutoCommit() and
Connection.setTransactionIsolation() and transaction state as
maintained by the protocol, rather than querying the database
or blindly sending commands to the database for commit() or
rollback() method calls?
Default: false
Since version: 3.1.7
useLocalTransactionState
Should the driver use the in-transaction state provided by
the MySQL protocol to determine if a commit() or rollback()
should actually be sent to the database?
Default: false
Since version: 5.1.7
prepStmtCacheSize
If prepared statement caching is enabled, how many prepared
statements should be cached?
Default: 25
Since version: 3.0.10
prepStmtCacheSqlLimit
If prepared statement caching is enabled, what's the largest
SQL the driver will cache the parsing for?
Default: 256
Since version: 3.0.10
parseInfoCacheFactory
Name of a class implementing
com.mysql.jdbc.CacheAdapterFactory, which will be used to
create caches for the parsed representation of client-side
prepared statements.
Default: com.mysql.jdbc.PerConnectionLRUFactory
Since version: 5.1.1
serverConfigCacheFactory
Name of a class implementing
com.mysql.jdbc.CacheAdapterFactory<String, Map<String,
String>>, which will be used to create caches for MySQL
server configuration values
Default: com.mysql.jdbc.PerVmServerConfigCacheFactory
Since version: 5.1.1
alwaysSendSetIsolation
Should the driver always communicate with the database when
Connection.setTransactionIsolation() is called? If set to
false, the driver will only communicate with the database
when the requested transaction isolation is different than
the whichever is newer, the last value that was set via
Connection.setTransactionIsolation(), or the value that was
read from the server when the connection was established.
Note that useLocalSessionState=true will force the same
behavior as alwaysSendSetIsolation=false, regardless of how
alwaysSendSetIsolation is set.
Default: true
Since version: 3.1.7
maintainTimeStats
Should the driver maintain various internal timers to enable
idle time calculations as well as more verbose error messages
when the connection to the server fails? Setting this
property to false removes at least two calls to
System.getCurrentTimeMillis() per query.
Default: true
Since version: 3.1.9
useCursorFetch
If connected to MySQL > 5.0.2, and setFetchSize() > 0 on a
statement, should that statement use cursor-based fetching to
retrieve rows?
Default: false
Since version: 5.0.0
blobSendChunkSize
Chunk size to use when sending BLOB/CLOBs via
ServerPreparedStatements. Note that this value cannot exceed
the value of "maxAllowedPacket" and, if that is the case,
then this value will be corrected automatically.
Default: 1048576
Since version: 3.1.9
cacheCallableStmts
Should the driver cache the parsing stage of
CallableStatements
Default: false
Since version: 3.1.2
cachePrepStmts
Should the driver cache the parsing stage of
PreparedStatements of client-side prepared statements, the
"check" for suitability of server-side prepared and
server-side prepared statements themselves?
Default: false
Since version: 3.0.10
cacheResultSetMetadata
Should the driver cache ResultSetMetaData for Statements and
PreparedStatements? (Req. JDK-1.4+, true/false, default
'false')
Default: false
Since version: 3.1.1
cacheServerConfiguration
Should the driver cache the results of 'SHOW VARIABLES' and
'SHOW COLLATION' on a per-URL basis?
Default: false
Since version: 3.1.5
defaultFetchSize
The driver will call setFetchSize(n) with this value on all
newly-created Statements
Default: 0
Since version: 3.1.9
dontCheckOnDuplicateKeyUpdateInSQL
Stops checking if every INSERT statement contains the "ON
DUPLICATE KEY UPDATE" clause. As a side effect, obtaining the
statement's generated keys information will return a list
where normally it wouldn't. Also be aware that, in this case,
the list of generated keys returned may not be accurate. The
effect of this property is canceled if set simultaneously
with 'rewriteBatchedStatements=true'.
Default: false
Since version: 5.1.32
dontTrackOpenResources
The JDBC specification requires the driver to automatically
track and close resources, however if your application
doesn't do a good job of explicitly calling close() on
statements or result sets, this can cause memory leakage.
Setting this property to true relaxes this constraint, and
can be more memory efficient for some applications. Also the
automatic closing of the Statement and current ResultSet in
Statement.closeOnCompletion() and Statement.getMoreResults
([Statement.CLOSE_CURRENT_RESULT |
Statement.CLOSE_ALL_RESULTS]), respectively, ceases to
happen. This property automatically sets
holdResultsOpenOverStatementClose=true.
Default: false
Since version: 3.1.7
dynamicCalendars
Should the driver retrieve the default calendar when
required, or cache it per connection/session?
Default: false
Since version: 3.1.5
elideSetAutoCommits
If using MySQL-4.1 or newer, should the driver only issue
'set autocommit=n' queries when the server's state doesn't
match the requested state by
Connection.setAutoCommit(boolean)?
Default: false
Since version: 3.1.3
enableEscapeProcessing
Sets the default escape processing behavior for Statement
objects. The method Statement.setEscapeProcessing() can be
used to specify the escape processing behavior for an
individual Statement object. Default escape processing
behavior in prepared statements must be defined with the
property 'processEscapeCodesForPrepStmts'.
Default: true
Since version: 5.1.37
enableQueryTimeouts
When enabled, query timeouts set via
Statement.setQueryTimeout() use a shared java.util.Timer
instance for scheduling. Even if the timeout doesn't expire
before the query is processed, there will be memory used by
the TimerTask for the given timeout which won't be reclaimed
until the time the timeout would have expired if it hadn't
been cancelled by the driver. High-load environments might
want to consider disabling this functionality.
Default: true
Since version: 5.0.6
holdResultsOpenOverStatementClose
Should the driver close result sets on Statement.close() as
required by the JDBC specification?
Default: false
Since version: 3.1.7
largeRowSizeThreshold
What size result set row should the JDBC driver consider
"large", and thus use a more memory-efficient way of
representing the row internally?
Default: 2048
Since version: 5.1.1
loadBalanceStrategy
If using a load-balanced connection to connect to SQL nodes
in a MySQL Cluster/NDB configuration (by using the URL prefix
"jdbc:mysql:loadbalance://"), which load balancing algorithm
should the driver use: (1) "random" - the driver will pick a
random host for each request. This tends to work better than
round-robin, as the randomness will somewhat account for
spreading loads where requests vary in response time, while
round-robin can sometimes lead to overloaded nodes if there
are variations in response times across the workload. (2)
"bestResponseTime" - the driver will route the request to the
host that had the best response time for the previous
transaction.
Default: random
Since version: 5.0.6
locatorFetchBufferSize
If 'emulateLocators' is configured to 'true', what size
buffer should be used when fetching BLOB data for
getBinaryInputStream?
Default: 1048576
Since version: 3.2.1
readOnlyPropagatesToServer
Should the driver issue appropriate statements to implicitly
set the transaction access mode on server side when
Connection.setReadOnly() is called? Setting this property to
'true' enables InnoDB read-only potential optimizations but
also requires an extra roundtrip to set the right transaction
state. Even if this property is set to 'false', the driver
will do its best effort to prevent the execution of
database-state-changing queries. Requires minimum of MySQL
5.6.
Default: true
Since version: 5.1.35
rewriteBatchedStatements
Should the driver use multiqueries (irregardless of the
setting of "allowMultiQueries") as well as rewriting of
prepared statements for INSERT into multi-value inserts when
executeBatch() is called? Notice that this has the potential
for SQL injection if using plain java.sql.Statements and your
code doesn't sanitize input correctly. Notice that for
prepared statements, server-side prepared statements can not
currently take advantage of this rewrite option, and that if
you don't specify stream lengths when using
PreparedStatement.set*Stream(), the driver won't be able to
determine the optimum number of parameters per batch and you
might receive an error from the driver that the resultant
packet is too large. Statement.getGeneratedKeys() for these
rewritten statements only works when the entire batch
includes INSERT statements. Please be aware using
rewriteBatchedStatements=true with INSERT .. ON DUPLICATE KEY
UPDATE that for rewritten statement server returns only one
value as sum of all affected (or found) rows in batch and it
isn't possible to map it correctly to initial statements; in
this case driver returns 0 as a result of each batch
statement if total count was 0, and the
Statement.SUCCESS_NO_INFO as a result of each batch statement
if total count was > 0.
Default: false
Since version: 3.1.13
useDirectRowUnpack
Use newer result set row unpacking code that skips a copy
from network buffers to a MySQL packet instance and instead
reads directly into the result set row data buffers.
Default: true
Since version: 5.1.1
useDynamicCharsetInfo
Should the driver use a per-connection cache of character set
information queried from the server when necessary, or use a
built-in static mapping that is more efficient, but isn't
aware of custom character sets or character sets implemented
after the release of the JDBC driver?
Default: true
Since version: 5.0.6
useFastDateParsing
Use internal String->Date/Time/Timestamp conversion routines
to avoid excessive object creation? This is part of the
legacy date-time code, thus the property has an effect only
when "useLegacyDatetimeCode=true."
Default: true
Since version: 5.0.5
useFastIntParsing
Use internal String->Integer conversion routines to avoid
excessive object creation?
Default: true
Since version: 3.1.4
useJvmCharsetConverters
Always use the character encoding routines built into the
JVM, rather than using lookup tables for single-byte
character sets?
Default: false
Since version: 5.0.1
useReadAheadInput
Use newer, optimized non-blocking, buffered input stream when
reading from the server?
Default: true
Since version: 3.1.5
Debugging/Profiling.
Properties and Descriptions
logger
The name of a class that implements "com.mysql.jdbc.log.Log"
that will be used to log messages to. (default is
"com.mysql.jdbc.log.StandardLogger", which logs to STDERR)
Default: com.mysql.jdbc.log.StandardLogger
Since version: 3.1.1
gatherPerfMetrics
Should the driver gather performance metrics, and report them
via the configured logger every 'reportMetricsIntervalMillis'
milliseconds?
Default: false
Since version: 3.1.2
profileSQL
Trace queries and their execution/fetch times to the
configured logger (true/false) defaults to 'false'
Default: false
Since version: 3.1.0
profileSql
Deprecated, use 'profileSQL' instead. Trace queries and their
execution/fetch times on STDERR (true/false) defaults to
'false'
Since version: 2.0.14
reportMetricsIntervalMillis
If 'gatherPerfMetrics' is enabled, how often should they be
logged (in ms)?
Default: 30000
Since version: 3.1.2
maxQuerySizeToLog
Controls the maximum length/size of a query that will get
logged when profiling or tracing
Default: 2048
Since version: 3.1.3
packetDebugBufferSize
The maximum number of packets to retain when
'enablePacketDebug' is true
Default: 20
Since version: 3.1.3
slowQueryThresholdMillis
If 'logSlowQueries' is enabled, how long should a query (in
ms) before it is logged as 'slow'?
Default: 2000
Since version: 3.1.2
slowQueryThresholdNanos
If 'useNanosForElapsedTime' is set to true, and this property
is set to a non-zero value, the driver will use this
threshold (in nanosecond units) to determine if a query was
slow.
Default: 0
Since version: 5.0.7
useUsageAdvisor
Should the driver issue 'usage' warnings advising proper and
efficient usage of JDBC and MySQL Connector/J to the log
(true/false, defaults to 'false')?
Default: false
Since version: 3.1.1
autoGenerateTestcaseScript
Should the driver dump the SQL it is executing, including
server-side prepared statements to STDERR?
Default: false
Since version: 3.1.9
autoSlowLog
Instead of using slowQueryThreshold* to determine if a query
is slow enough to be logged, maintain statistics that allow
the driver to determine queries that are outside the 99th
percentile?
Default: true
Since version: 5.1.4
clientInfoProvider
The name of a class that implements the
com.mysql.jdbc.JDBC4ClientInfoProvider interface in order to
support JDBC-4.0's Connection.get/setClientInfo() methods
Default: com.mysql.jdbc.JDBC4CommentClientInfoProvider
Since version: 5.1.0
dumpMetadataOnColumnNotFound
Should the driver dump the field-level metadata of a result
set into the exception message when ResultSet.findColumn()
fails?
Default: false
Since version: 3.1.13
dumpQueriesOnException
Should the driver dump the contents of the query sent to the
server in the message for SQLExceptions?
Default: false
Since version: 3.1.3
enablePacketDebug
When enabled, a ring-buffer of 'packetDebugBufferSize'
packets will be kept, and dumped when exceptions are thrown
in key areas in the driver's code
Default: false
Since version: 3.1.3
explainSlowQueries
If 'logSlowQueries' is enabled, should the driver
automatically issue an 'EXPLAIN' on the server and send the
results to the configured log at a WARN level?
Default: false
Since version: 3.1.2
includeInnodbStatusInDeadlockExceptions
Include the output of "SHOW ENGINE INNODB STATUS" in
exception messages when deadlock exceptions are detected?
Default: false
Since version: 5.0.7
includeThreadDumpInDeadlockExceptions
Include a current Java thread dump in exception messages when
deadlock exceptions are detected?
Default: false
Since version: 5.1.15
includeThreadNamesAsStatementComment
Include the name of the current thread as a comment visible
in "SHOW PROCESSLIST", or in Innodb deadlock dumps, useful in
correlation with
"includeInnodbStatusInDeadlockExceptions=true" and
"includeThreadDumpInDeadlockExceptions=true".
Default: false
Since version: 5.1.15
logSlowQueries
Should queries that take longer than
'slowQueryThresholdMillis' be logged?
Default: false
Since version: 3.1.2
logXaCommands
Should the driver log XA commands sent by MysqlXaConnection
to the server, at the DEBUG level of logging?
Default: false
Since version: 5.0.5
profilerEventHandler
Name of a class that implements the interface
com.mysql.jdbc.profiler.ProfilerEventHandler that will be
used to handle profiling/tracing events.
Default: com.mysql.jdbc.profiler.LoggingProfilerEventHandler
Since version: 5.1.6
resultSetSizeThreshold
If the usage advisor is enabled, how many rows should a
result set contain before the driver warns that it is
suspiciously large?
Default: 100
Since version: 5.0.5
traceProtocol
Should trace-level network protocol be logged?
Default: false
Since version: 3.1.2
useNanosForElapsedTime
For profiling/debugging functionality that measures elapsed
time, should the driver try to use nanoseconds resolution if
available (JDK >= 1.5)?
Default: false
Since version: 5.0.7
Miscellaneous.
Properties and Descriptions
useUnicode
Should the driver use Unicode character encodings when
handling strings? Should only be used when the driver can't
determine the character set mapping, or you are trying to
'force' the driver to use a character set that MySQL either
doesn't natively support (such as UTF-8), true/false,
defaults to 'true'
Default: true
Since version: 1.1g
characterEncoding
If 'useUnicode' is set to true, what character encoding
should the driver use when dealing with strings? (defaults is
to 'autodetect')
Since version: 1.1g
characterSetResults
Character set to tell the server to return results as.
Since version: 3.0.13
connectionAttributes
A comma-delimited list of user-defined key:value pairs (in
addition to standard MySQL-defined key:value pairs) to be
passed to MySQL Server for display as connection attributes
in the PERFORMANCE_SCHEMA.SESSION_CONNECT_ATTRS table.
Example usage: connectionAttributes=key1:value1,key2:value2
This functionality is available for use with MySQL Server
version 5.6 or later only. Earlier versions of MySQL Server
do not support connection attributes, causing this
configuration option to be ignored. Setting
connectionAttributes=none will cause connection attribute
processing to be bypassed, for situations where Connection
creation/initialization speed is critical.
Since version: 5.1.25
connectionCollation
If set, tells the server to use this collation via 'set
collation_connection'
Since version: 3.0.13
useBlobToStoreUTF8OutsideBMP
Tells the driver to treat [MEDIUM/LONG]BLOB columns as
[LONG]VARCHAR columns holding text encoded in UTF-8 that has
characters outside the BMP (4-byte encodings), which MySQL
server can't handle natively.
Default: false
Since version: 5.1.3
utf8OutsideBmpExcludedColumnNamePattern
When "useBlobToStoreUTF8OutsideBMP" is set to "true", column
names matching the given regex will still be treated as BLOBs
unless they match the regex specified for
"utf8OutsideBmpIncludedColumnNamePattern". The regex must
follow the patterns used for the java.util.regex package.
Since version: 5.1.3
utf8OutsideBmpIncludedColumnNamePattern
Used to specify exclusion rules to
"utf8OutsideBmpExcludedColumnNamePattern". The regex must
follow the patterns used for the java.util.regex package.
Since version: 5.1.3
loadBalanceEnableJMX
Enables JMX-based management of load-balanced connection
groups, including live addition/removal of hosts from
load-balancing pool.
Default: false
Since version: 5.1.13
sessionVariables
A comma-separated list of name/value pairs to be sent as SET
SESSION ... to the server when the driver connects.
Since version: 3.1.8
useColumnNamesInFindColumn
Prior to JDBC-4.0, the JDBC specification had a bug related
to what could be given as a "column name" to ResultSet
methods like findColumn(), or getters that took a String
property. JDBC-4.0 clarified "column name" to mean the label,
as given in an "AS" clause and returned by
ResultSetMetaData.getColumnLabel(), and if no AS clause, the
column name. Setting this property to "true" will give
behavior that is congruent to JDBC-3.0 and earlier versions
of the JDBC specification, but which because of the
specification bug could give unexpected results. This
property is preferred over "useOldAliasMetadataBehavior"
unless you need the specific behavior that it provides with
respect to ResultSetMetadata.
Default: false
Since version: 5.1.7
allowNanAndInf
Should the driver allow NaN or +/- INF values in
PreparedStatement.setDouble()?
Default: false
Since version: 3.1.5
autoClosePStmtStreams
Should the driver automatically call .close() on
streams/readers passed as arguments via set*() methods?
Default: false
Since version: 3.1.12
autoDeserialize
Should the driver automatically detect and de-serialize
objects stored in BLOB fields?
Default: false
Since version: 3.1.5
blobsAreStrings
Should the driver always treat BLOBs as Strings -
specifically to work around dubious metadata returned by the
server for GROUP BY clauses?
Default: false
Since version: 5.0.8
cacheDefaultTimezone
Caches client's default time zone. This results in better
performance when dealing with time zone conversions in Date
and Time data types, however it won't be aware of time zone
changes if they happen at runtime.
Default: true
Since version: 5.1.35
capitalizeTypeNames
Capitalize type names in DatabaseMetaData? (usually only
useful when using WebObjects, true/false, defaults to
'false')
Default: true
Since version: 2.0.7
clobCharacterEncoding
The character encoding to use for sending and retrieving
TEXT, MEDIUMTEXT and LONGTEXT values instead of the
configured connection characterEncoding
Since version: 5.0.0
clobberStreamingResults
This will cause a 'streaming' ResultSet to be automatically
closed, and any outstanding data still streaming from the
server to be discarded if another query is executed before
all the data has been read from the server.
Default: false
Since version: 3.0.9
compensateOnDuplicateKeyUpdateCounts
Should the driver compensate for the update counts of "ON
DUPLICATE KEY" INSERT statements (2 = 1, 0 = 1) when using
prepared statements?
Default: false
Since version: 5.1.7
continueBatchOnError
Should the driver continue processing batch commands if one
statement fails. The JDBC spec allows either way (defaults to
'true').
Default: true
Since version: 3.0.3
createDatabaseIfNotExist
Creates the database given in the URL if it doesn't yet
exist. Assumes the configured user has permissions to create
databases.
Default: false
Since version: 3.1.9
detectCustomCollations
Should the driver detect custom charsets/collations installed
on server (true/false, defaults to 'false'). If this option
set to 'true' driver gets actual charsets/collations from
server each time connection establishes. This could slow down
connection initialization significantly.
Default: false
Since version: 5.1.29
emptyStringsConvertToZero
Should the driver allow conversions from empty string fields
to numeric values of '0'?
Default: true
Since version: 3.1.8
emulateLocators
Should the driver emulate java.sql.Blobs with locators? With
this feature enabled, the driver will delay loading the
actual Blob data until the one of the retrieval methods
(getInputStream(), getBytes(), and so forth) on the blob data
stream has been accessed. For this to work, you must use a
column alias with the value of the column to the actual name
of the Blob. The feature also has the following restrictions:
The SELECT that created the result set must reference only
one table, the table must have a primary key; the SELECT must
alias the original blob column name, specified as a string,
to an alternate name; the SELECT must cover all columns that
make up the primary key.
Default: false
Since version: 3.1.0
emulateUnsupportedPstmts
Should the driver detect prepared statements that are not
supported by the server, and replace them with client-side
emulated versions?
Default: true
Since version: 3.1.7
exceptionInterceptors
Comma-delimited list of classes that implement
com.mysql.jdbc.ExceptionInterceptor. These classes will be
instantiated one per Connection instance, and all
SQLExceptions thrown by the driver will be allowed to be
intercepted by these interceptors, in a chained fashion, with
the first class listed as the head of the chain.
Since version: 5.1.8
functionsNeverReturnBlobs
Should the driver always treat data from functions returning
BLOBs as Strings - specifically to work around dubious
metadata returned by the server for GROUP BY clauses?
Default: false
Since version: 5.0.8
generateSimpleParameterMetadata
Should the driver generate simplified parameter metadata for
PreparedStatements when no metadata is available either
because the server couldn't support preparing the statement,
or server-side prepared statements are disabled?
Default: false
Since version: 5.0.5
getProceduresReturnsFunctions
Pre-JDBC4 DatabaseMetaData API has only the getProcedures()
and getProcedureColumns() methods, so they return metadata
info for both stored procedures and functions. JDBC4 was
extended with the getFunctions() and getFunctionColumns()
methods and the expected behaviours of previous methods are
not well defined. For JDBC4 and higher, default 'true' value
of the option means that calls of
DatabaseMetaData.getProcedures() and
DatabaseMetaData.getProcedureColumns() return metadata for
both procedures and functions as before, keeping backward
compatibility. Setting this property to 'false' decouples
Connector/J from its pre-JDBC4 behaviours for
DatabaseMetaData.getProcedures() and
DatabaseMetaData.getProcedureColumns(), forcing them to
return metadata for procedures only.
Default: true
Since version: 5.1.26
ignoreNonTxTables
Ignore non-transactional table warning for rollback?
(defaults to 'false').
Default: false
Since version: 3.0.9
jdbcCompliantTruncation
Should the driver throw java.sql.DataTruncation exceptions
when data is truncated as is required by the JDBC
specification when connected to a server that supports
warnings (MySQL 4.1.0 and newer)? This property has no effect
if the server sql-mode includes STRICT_TRANS_TABLES.
Default: true
Since version: 3.1.2
loadBalanceAutoCommitStatementRegex
When load-balancing is enabled for auto-commit statements
(via loadBalanceAutoCommitStatementThreshold), the statement
counter will only increment when the SQL matches the regular
expression. By default, every statement issued matches.
Since version: 5.1.15
loadBalanceAutoCommitStatementThreshold
When auto-commit is enabled, the number of statements which
should be executed before triggering load-balancing to
rebalance. Default value of 0 causes load-balanced
connections to only rebalance when exceptions are
encountered, or auto-commit is disabled and transactions are
explicitly committed or rolled back.
Default: 0
Since version: 5.1.15
loadBalanceBlacklistTimeout
Time in milliseconds between checks of servers which are
unavailable, by controlling how long a server lives in the
global blacklist.
Default: 0
Since version: 5.1.0
loadBalanceConnectionGroup
Logical group of load-balanced connections within a
classloader, used to manage different groups independently.
If not specified, live management of load-balanced
connections is disabled.
Since version: 5.1.13
loadBalanceExceptionChecker
Fully-qualified class name of custom exception checker. The
class must implement
com.mysql.jdbc.LoadBalanceExceptionChecker interface, and is
used to inspect SQLExceptions and determine whether they
should trigger fail-over to another host in a load-balanced
deployment.
Default: com.mysql.jdbc.StandardLoadBalanceExceptionChecker
Since version: 5.1.13
loadBalancePingTimeout
Time in milliseconds to wait for ping response from each of
load-balanced physical connections when using load-balanced
Connection.
Default: 0
Since version: 5.1.13
loadBalanceSQLExceptionSubclassFailover
Comma-delimited list of classes/interfaces used by default
load-balanced exception checker to determine whether a given
SQLException should trigger failover. The comparison is done
using Class.isInstance(SQLException) using the thrown
SQLException.
Since version: 5.1.13
loadBalanceSQLStateFailover
Comma-delimited list of SQLState codes used by default
load-balanced exception checker to determine whether a given
SQLException should trigger failover. The SQLState of a given
SQLException is evaluated to determine whether it begins with
any value in the comma-delimited list.
Since version: 5.1.13
loadBalanceValidateConnectionOnSwapServer
Should the load-balanced Connection explicitly check whether
the connection is live when swapping to a new physical
connection at commit/rollback?
Default: false
Since version: 5.1.13
maxRows
The maximum number of rows to return (0, the default means
return all rows).
Default: -1
Since version: all versions
netTimeoutForStreamingResults
What value should the driver automatically set the server
setting 'net_write_timeout' to when the streaming result sets
feature is in use? (value has unit of seconds, the value '0'
means the driver will not try and adjust this value)
Default: 600
Since version: 5.1.0
noAccessToProcedureBodies
When determining procedure parameter types for
CallableStatements, and the connected user can't access
procedure bodies through "SHOW CREATE PROCEDURE" or select on
mysql.proc should the driver instead create basic metadata
(all parameters reported as IN VARCHARs, but allowing
registerOutParameter() to be called on them anyway) instead
of throwing an exception?
Default: false
Since version: 5.0.3
noDatetimeStringSync
Don't ensure that
ResultSet.getDatetimeType().toString().equals(ResultSet.getSt
ring())
Default: false
Since version: 3.1.7
noTimezoneConversionForDateType
Don't convert DATE values using the server time zone if
'useTimezone'='true' or 'useLegacyDatetimeCode'='false'
Default: true
Since version: 5.1.35
noTimezoneConversionForTimeType
Don't convert TIME values using the server time zone if
'useTimezone'='true'
Default: false
Since version: 5.0.0
nullCatalogMeansCurrent
When DatabaseMetadataMethods ask for a 'catalog' parameter,
does the value null mean use the current catalog? (this is
not JDBC-compliant, but follows legacy behavior from earlier
versions of the driver)
Default: true
Since version: 3.1.8
nullNamePatternMatchesAll
Should DatabaseMetaData methods that accept *pattern
parameters treat null the same as '%' (this is not
JDBC-compliant, however older versions of the driver accepted
this departure from the specification)
Default: true
Since version: 3.1.8
overrideSupportsIntegrityEnhancementFacility
Should the driver return "true" for
DatabaseMetaData.supportsIntegrityEnhancementFacility() even
if the database doesn't support it to workaround applications
that require this method to return "true" to signal support
of foreign keys, even though the SQL specification states
that this facility contains much more than just foreign key
support (one such application being OpenOffice)?
Default: false
Since version: 3.1.12
padCharsWithSpace
If a result set column has the CHAR type and the value does
not fill the amount of characters specified in the DDL for
the column, should the driver pad the remaining characters
with space (for ANSI compliance)?
Default: false
Since version: 5.0.6
pedantic
Follow the JDBC spec to the letter.
Default: false
Since version: 3.0.0
pinGlobalTxToPhysicalConnection
When using XAConnections, should the driver ensure that
operations on a given XID are always routed to the same
physical connection? This allows the XAConnection to support
"XA START ... JOIN" after "XA END" has been called
Default: false
Since version: 5.0.1
populateInsertRowWithDefaultValues
When using ResultSets that are CONCUR_UPDATABLE, should the
driver pre-populate the "insert" row with default values from
the DDL for the table used in the query so those values are
immediately available for ResultSet accessors? This
functionality requires a call to the database for metadata
each time a result set of this type is created. If disabled
(the default), the default values will be populated by the an
internal call to refreshRow() which pulls back default values
and/or values changed by triggers.
Default: false
Since version: 5.0.5
processEscapeCodesForPrepStmts
Should the driver process escape codes in queries that are
prepared? Default escape processing behavior in non-prepared
statements must be defined with the property
'enableEscapeProcessing'.
Default: true
Since version: 3.1.12
queryTimeoutKillsConnection
If the timeout given in Statement.setQueryTimeout() expires,
should the driver forcibly abort the Connection instead of
attempting to abort the query?
Default: false
Since version: 5.1.9
relaxAutoCommit
If the version of MySQL the driver connects to does not
support transactions, still allow calls to commit(),
rollback() and setAutoCommit() (true/false, defaults to
'false')?
Default: false
Since version: 2.0.13
retainStatementAfterResultSetClose
Should the driver retain the Statement reference in a
ResultSet after ResultSet.close() has been called. This is
not JDBC-compliant after JDBC-4.0.
Default: false
Since version: 3.1.11
rollbackOnPooledClose
Should the driver issue a rollback() when the logical
connection in a pool is closed?
Default: true
Since version: 3.0.15
runningCTS13
Enables workarounds for bugs in Sun's JDBC compliance
testsuite version 1.3
Default: false
Since version: 3.1.7
sendFractionalSeconds
Send fractional part from TIMESTAMP seconds. If set to false,
the nanoseconds value of TIMESTAMP values will be truncated
before sending any data to the server. This option applies
only to prepared statements, callable statements or updatable
result sets.
Default: true
Since version: 5.1.37
serverTimezone
Override detection/mapping of time zone. Used when time zone
from server doesn't map to Java time zone
Since version: 3.0.2
statementInterceptors
A comma-delimited list of classes that implement
"com.mysql.jdbc.StatementInterceptor" that should be placed
"in between" query execution to influence the results.
StatementInterceptors are "chainable", the results returned
by the "current" interceptor will be passed on to the next in
in the chain, from left-to-right order, as specified in this
property.
Since version: 5.1.1
strictFloatingPoint
Used only in older versions of compliance test
Default: false
Since version: 3.0.0
strictUpdates
Should the driver do strict checking (all primary keys
selected) of updatable result sets (true, false, defaults to
'true')?
Default: true
Since version: 3.0.4
tinyInt1isBit
Should the driver treat the datatype TINYINT(1) as the BIT
type (because the server silently converts BIT -> TINYINT(1)
when creating tables)?
Default: true
Since version: 3.0.16
transformedBitIsBoolean
If the driver converts TINYINT(1) to a different type, should
it use BOOLEAN instead of BIT for future compatibility with
MySQL-5.0, as MySQL-5.0 has a BIT type?
Default: false
Since version: 3.1.9
treatUtilDateAsTimestamp
Should the driver treat java.util.Date as a TIMESTAMP for the
purposes of PreparedStatement.setObject()?
Default: true
Since version: 5.0.5
ultraDevHack
Create PreparedStatements for prepareCall() when required,
because UltraDev is broken and issues a prepareCall() for
_all_ statements? (true/false, defaults to 'false')
Default: false
Since version: 2.0.3
useAffectedRows
Don't set the CLIENT_FOUND_ROWS flag when connecting to the
server (not JDBC-compliant, will break most applications that
rely on "found" rows vs. "affected rows" for DML statements),
but does cause "correct" update counts from "INSERT ... ON
DUPLICATE KEY UPDATE" statements to be returned by the
server.
Default: false
Since version: 5.1.7
useGmtMillisForDatetimes
Convert between session time zone and GMT before creating
Date and Timestamp instances (value of 'false' leads to
legacy behavior, 'true' leads to more JDBC-compliant
behavior)? This is part of the legacy date-time code, thus
the property has an effect only when
"useLegacyDatetimeCode=true."
Default: false
Since version: 3.1.12
useHostsInPrivileges
Add '@hostname' to users in
DatabaseMetaData.getColumn/TablePrivileges() (true/false),
defaults to 'true'.
Default: true
Since version: 3.0.2
useInformationSchema
When connected to MySQL-5.0.7 or newer, should the driver use
the INFORMATION_SCHEMA to derive information used by
DatabaseMetaData?
Default: false
Since version: 5.0.0
useJDBCCompliantTimezoneShift
Should the driver use JDBC-compliant rules when converting
TIME/TIMESTAMP/DATETIME values' time zone information for
those JDBC arguments which take a java.util.Calendar
argument? This is part of the legacy date-time code, thus the
property has an effect only when
"useLegacyDatetimeCode=true."
Default: false
Since version: 5.0.0
useLegacyDatetimeCode
Use code for DATE/TIME/DATETIME/TIMESTAMP handling in result
sets and statements that consistently handles time zone
conversions from client to server and back again, or use the
legacy code for these datatypes that has been in the driver
for backwards-compatibility? Setting this property to 'false'
voids the effects of "useTimezone,"
"useJDBCCompliantTimezoneShift," "useGmtMillisForDatetimes,"
and "useFastDateParsing."
Default: true
Since version: 5.1.6
useOldAliasMetadataBehavior
Should the driver use the legacy behavior for "AS" clauses on
columns and tables, and only return aliases (if any) for
ResultSetMetaData.getColumnName() or
ResultSetMetaData.getTableName() rather than the original
column/table name? In 5.0.x, the default value was true.
Default: false
Since version: 5.0.4
useOldUTF8Behavior
Use the UTF-8 behavior the driver did when communicating with
4.0 and older servers
Default: false
Since version: 3.1.6
useOnlyServerErrorMessages
Don't prepend 'standard' SQLState error messages to error
messages returned by the server.
Default: true
Since version: 3.0.15
useSSPSCompatibleTimezoneShift
If migrating from an environment that was using server-side
prepared statements, and the configuration property
"useJDBCCompliantTimeZoneShift" set to "true", use compatible
behavior when not using server-side prepared statements when
sending TIMESTAMP values to the MySQL server.
Default: false
Since version: 5.0.5
useServerPrepStmts
Use server-side prepared statements if the server supports
them?
Default: false
Since version: 3.1.0
useSqlStateCodes
Use SQL Standard state codes instead of 'legacy' X/Open/SQL
state codes (true/false), default is 'true'
Default: true
Since version: 3.1.3
useStreamLengthsInPrepStmts
Honor stream length parameter in
PreparedStatement/ResultSet.setXXXStream() method calls
(true/false, defaults to 'true')?
Default: true
Since version: 3.0.2
useTimezone
Convert time/date types between client and server time zones
(true/false, defaults to 'false')? This is part of the legacy
date-time code, thus the property has an effect only when
"useLegacyDatetimeCode=true."
Default: false
Since version: 3.0.2
useUnbufferedInput
Don't use BufferedInputStream for reading data from the
server
Default: true
Since version: 3.0.11
yearIsDateType
Should the JDBC driver treat the MySQL type "YEAR" as a
java.sql.Date, or as a SHORT?
Default: true
Since version: 3.1.9
zeroDateTimeBehavior
What should happen when the driver encounters DATETIME values
that are composed entirely of zeros (used by MySQL to
represent invalid dates)? Valid values are "exception",
"round" and "convertToNull".
Default: exception
Since version: 3.1.4
Connector/J also supports access to MySQL using named pipes
on Windows platforms with the NamedPipeSocketFactory as a
plugin-socket factory. If you do not use a namedPipePath
property, the default of '\\.\pipe\MySQL' is used. If you use
the NamedPipeSocketFactory, the host name and port number
values in the JDBC URL are ignored. To enable this feature,
set the socketFactory property:
socketFactory=com.mysql.jdbc.NamedPipeSocketFactory
Named pipes only work when connecting to a MySQL server on
the same physical machine where the JDBC driver is running.
In simple performance tests, named pipe access is between
30%-50% faster than the standard TCP/IP access. However, this
varies per system, and named pipes are slower than TCP/IP in
many Windows configurations.
To create your own socket factories, follow the example code
in com.mysql.jdbc.NamedPipeSocketFactory, or
com.mysql.jdbc.StandardSocketFactory.
5.1.1 Properties Files for the useConfigs Option
The useConfigs connection option is convenient shorthand for
specifying combinations of options for particular scenarios.
The argument values you can use with this option correspond
to the names of .properties files within the Connector/J
mysql-connector-java-version-bin.jar JAR file. For example,
the Connector/J 5.1.9 driver includes the following
configuration properties files:
$ unzip mysql-connector-java-5.1.19-bin.jar '*/configs/*'
Archive: mysql-connector-java-5.1.19-bin.jar
creating: com/mysql/jdbc/configs/
inflating: com/mysql/jdbc/configs/3-0-Compat.properties
inflating: com/mysql/jdbc/configs/5-0-Compat.properties
inflating: com/mysql/jdbc/configs/clusterBase.properties
inflating: com/mysql/jdbc/configs/coldFusion.properties
inflating: com/mysql/jdbc/configs/fullDebug.properties
inflating: com/mysql/jdbc/configs/maxPerformance.properties
inflating: com/mysql/jdbc/configs/solarisMaxPerformance.properties
To specify one of these combinations of options, specify
useConfigs=3-0-Compat, useConfigs=maxPerformance, and so on.
The following sections show the options that are part of each
useConfigs setting. For the details of why each one is
included, see the comments in the .properties files.
3-0-Compat
emptyStringsConvertToZero=true
jdbcCompliantTruncation=false
noDatetimeStringSync=true
nullCatalogMeansCurrent=true
nullNamePatternMatchesAll=true
transformedBitIsBoolean=false
dontTrackOpenResources=true
zeroDateTimeBehavior=convertToNull
useServerPrepStmts=false
autoClosePStmtStreams=true
processEscapeCodesForPrepStmts=false
useFastDateParsing=false
populateInsertRowWithDefaultValues=false
useDirectRowUnpack=false
5-0-Compat
useDirectRowUnpack=false
clusterBase
autoReconnect=true
failOverReadOnly=false
roundRobinLoadBalance=true
coldFusion
useDynamicCharsetInfo=false
alwaysSendSetIsolation=false
useLocalSessionState=true
autoReconnect=true
fullDebug
profileSQL=true
gatherPerfMetrics=true
useUsageAdvisor=true
logSlowQueries=true
explainSlowQueries=true
maxPerformance
cachePrepStmts=true
cacheCallableStmts=true
cacheServerConfiguration=true
useLocalSessionState=true
elideSetAutoCommits=true
alwaysSendSetIsolation=false
enableQueryTimeouts=false
solarisMaxPerformance
useUnbufferedInput=false
useReadAheadInput=false
maintainTimeStats=false
5.2 JDBC API Implementation Notes
MySQL Connector/J, as a rigorous implementation of the JDBC
API
(http://www.oracle.com/technetwork/java/javase/jdbc/index.htm
l), passes all of the tests in the publicly available version
of Oracle's JDBC compliance test suite. The JDBC
specification is flexible on how certain functionality should
be implemented. This section gives details on an
interface-by-interface level about implementation decisions
that might affect how you code applications with MySQL
Connector/J.
* BLOB
Starting with Connector/J version 3.1.0, you can emulate
BLOBs with locators by adding the property
emulateLocators=true to your JDBC URL. Using this method,
the driver will delay loading the actual BLOB data until
you retrieve the other data and then use retrieval
methods (getInputStream(), getBytes(), and so forth) on
the BLOB data stream.
You must use a column alias with the value of the column
to the actual name of the BLOB, for example:
SELECT id, 'data' as blob_data from blobtable
You must also follow these rules:
+ The SELECT
(http://dev.mysql.com/doc/refman/5.7/en/select.html)
must reference only one table. The table must have a
primary key
(http://dev.mysql.com/doc/refman/5.7/en/glossary.htm
l#glos_primary_key).
+ The SELECT
(http://dev.mysql.com/doc/refman/5.7/en/select.html)
must alias the original BLOB column name, specified
as a string, to an alternate name.
+ The SELECT
(http://dev.mysql.com/doc/refman/5.7/en/select.html)
must cover all columns that make up the primary key.
The BLOB implementation does not allow in-place
modification (they are copies, as reported by the
DatabaseMetaData.locatorsUpdateCopies() method). Because
of this, use the corresponding
PreparedStatement.setBlob() or ResultSet.updateBlob() (in
the case of updatable result sets) methods to save
changes back to the database.
* CallableStatement
Starting with Connector/J 3.1.1, stored procedures are
supported when connecting to MySQL version 5.0 or newer
using the CallableStatement interface. Currently, the
getParameterMetaData() method of CallableStatement is not
supported.
* CLOB
The CLOB implementation does not allow in-place
modification (they are copies, as reported by the
DatabaseMetaData.locatorsUpdateCopies() method). Because
of this, use the PreparedStatement.setClob() method to
save changes back to the database. The JDBC API does not
have a ResultSet.updateClob() method.
* Connection
Unlike the pre-Connector/J JDBC driver (MM.MySQL), the
isClosed() method does not ping the server to determine
if it is available. In accordance with the JDBC
specification, it only returns true if closed() has been
called on the connection. If you need to determine if the
connection is still valid, issue a simple query, such as
SELECT 1. The driver will throw an exception if the
connection is no longer valid.
* DatabaseMetaData
Foreign key
(http://dev.mysql.com/doc/refman/5.7/en/glossary.html#glo
s_foreign_key) information
(getImportedKeys()/getExportedKeys() and
getCrossReference()) is only available from InnoDB
(http://dev.mysql.com/doc/refman/5.7/en/innodb-storage-en
gine.html) tables. The driver uses SHOW CREATE TABLE
(http://dev.mysql.com/doc/refman/5.7/en/show-create-table
.html) to retrieve this information, so if any other
storage engines add support for foreign keys, the driver
would transparently support them as well.
* PreparedStatement
PreparedStatements are implemented by the driver, as
MySQL does not have a prepared statement feature. Because
of this, the driver does not implement
getParameterMetaData() or getMetaData() as it would
require the driver to have a complete SQL parser in the
client.
Starting with version 3.1.0 MySQL Connector/J,
server-side prepared statements and binary-encoded result
sets are used when the server supports them.
Take care when using a server-side prepared statement
with large parameters that are set using
setBinaryStream(), setAsciiStream(), setUnicodeStream(),
setBlob(), or setClob(). To re-execute the statement with
any large parameter changed to a nonlarge parameter, call
clearParameters() and set all parameters again. The
reason for this is as follows:
+ During both server-side prepared statements and
client-side emulation, large data is exchanged only
when PreparedStatement.execute() is called.
+ Once that has been done, the stream used to read the
data on the client side is closed (as per the JDBC
spec), and cannot be read from again.
+ If a parameter changes from large to nonlarge, the
driver must reset the server-side state of the
prepared statement to allow the parameter that is
being changed to take the place of the prior large
value. This removes all of the large data that has
already been sent to the server, thus requiring the
data to be re-sent, using the setBinaryStream(),
setAsciiStream(), setUnicodeStream(), setBlob() or
setClob() method.
Consequently, to change the type of a parameter to a
nonlarge one, you must call clearParameters() and set all
parameters of the prepared statement again before it can
be re-executed.
* ResultSet
By default, ResultSets are completely retrieved and
stored in memory. In most cases this is the most
efficient way to operate and, due to the design of the
MySQL network protocol, is easier to implement. If you
are working with ResultSets that have a large number of
rows or large values and cannot allocate heap space in
your JVM for the memory required, you can tell the driver
to stream the results back one row at a time.
To enable this functionality, create a Statement instance
in the following manner:
stmt = conn.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY,
java.sql.ResultSet.CONCUR_READ_ONLY);
stmt.setFetchSize(Integer.MIN_VALUE);
The combination of a forward-only, read-only result set,
with a fetch size of Integer.MIN_VALUE serves as a signal
to the driver to stream result sets row-by-row. After
this, any result sets created with the statement will be
retrieved row-by-row.
There are some caveats with this approach. You must read
all of the rows in the result set (or close it) before
you can issue any other queries on the connection, or an
exception will be thrown.
The earliest the locks these statements hold can be
released (whether they be MyISAM table-level locks or
row-level locks in some other storage engine such as
InnoDB) is when the statement completes.
If the statement is within scope of a transaction, then
locks are released when the transaction completes (which
implies that the statement needs to complete first). As
with most other databases, statements are not complete
until all the results pending on the statement are read
or the active result set for the statement is closed.
Therefore, if using streaming results, process them as
quickly as possible if you want to maintain concurrent
access to the tables referenced by the statement
producing the result set.
* ResultSetMetaData
The isAutoIncrement() method only works when using MySQL
servers 4.0 and newer.
* Statement
When using versions of the JDBC driver earlier than
3.2.1, and connected to server versions earlier than
5.0.3, the setFetchSize() method has no effect, other
than to toggle result set streaming as described above.
Connector/J 5.0.0 and later include support for both
Statement.cancel() and Statement.setQueryTimeout(). Both
require MySQL 5.0.0 or newer server, and require a
separate connection to issue the KILL QUERY
(http://dev.mysql.com/doc/refman/5.7/en/kill.html)
statement. In the case of setQueryTimeout(), the
implementation creates an additional thread to handle the
timeout functionality.
Note
Failures to cancel the statement for setQueryTimeout()
may manifest themselves as RuntimeException rather than
failing silently, as there is currently no way to unblock
the thread that is executing the query being cancelled
due to timeout expiration and have it throw the exception
instead.
Note
The MySQL statement KILL QUERY
(http://dev.mysql.com/doc/refman/5.7/en/kill.html) (which
is what the driver uses to implement Statement.cancel())
is non-deterministic; thus, avoid the use of
Statement.cancel() if possible. If no query is in
process, the next query issued will be killed by the
server. This race condition is guarded against as of
Connector/J 5.1.18.
MySQL does not support SQL cursors, and the JDBC driver
doesn't emulate them, so setCursorName() has no effect.
Connector/J 5.1.3 and later include two additional
methods:
+ setLocalInfileInputStream() sets an InputStream
instance that will be used to send data to the MySQL
server for a LOAD DATA LOCAL INFILE
(http://dev.mysql.com/doc/refman/5.7/en/load-data.ht
ml) statement rather than a FileInputStream or
URLInputStream that represents the path given as an
argument to the statement.
This stream will be read to completion upon
execution of a LOAD DATA LOCAL INFILE
(http://dev.mysql.com/doc/refman/5.7/en/load-data.ht
ml) statement, and will automatically be closed by
the driver, so it needs to be reset before each call
to execute*() that would cause the MySQL server to
request data to fulfill the request for LOAD DATA
LOCAL INFILE
(http://dev.mysql.com/doc/refman/5.7/en/load-data.ht
ml).
If this value is set to NULL, the driver will revert
to using a FileInputStream or URLInputStream as
required.
+ getLocalInfileInputStream() returns the InputStream
instance that will be used to send data in response
to a LOAD DATA LOCAL INFILE
(http://dev.mysql.com/doc/refman/5.7/en/load-data.ht
ml) statement.
This method returns NULL if no such stream has been
set using setLocalInfileInputStream().
5.3 Java, JDBC and MySQL Types
MySQL Connector/J is flexible in the way it handles
conversions between MySQL data types and Java data types.
In general, any MySQL data type can be converted to a
java.lang.String, and any numeric type can be converted to
any of the Java numeric types, although round-off, overflow,
or loss of precision may occur.
Note
All TEXT types return Types.LONGVARCHAR with different
getPrecision() values (65535, 255, 16777215, and 2147483647
respectively) with getColumnType() returning -1. This
behavior is intentional even though TINYTEXT does not fall,
regarding to its size, within the LONGVARCHAR category. This
is to avoid different handling inside the same base type. And
getColumnType() returns -1 because the internal server
handling is of type TEXT, which is similar to BLOB.
Also note that getColumnTypeName() will return VARCHAR even
though getColumnType() returns Types.LONGVARCHAR, because
VARCHAR is the designated column database-specific name for
this type.
Starting with Connector/J 3.1.0, the JDBC driver issues
warnings or throws DataTruncation exceptions as is required
by the JDBC specification unless the connection was
configured not to do so by using the property
jdbcCompliantTruncation and setting it to false.
The conversions that are always guaranteed to work are listed
in the following table. The first column lists one or more
MySQL data types, and the second column lists one or more
Java types to which the MySQL types can be converted.
Table 5.1 Connection Properties - Miscellaneous
These MySQL Data Types Can always be converted to these Java
types
CHAR, VARCHAR, BLOB, TEXT, ENUM, and SET java.lang.String,
java.io.InputStream, java.io.Reader, java.sql.Blob,
java.sql.Clob
FLOAT, REAL, DOUBLE PRECISION, NUMERIC, DECIMAL, TINYINT,
SMALLINT, MEDIUMINT, INTEGER, BIGINT java.lang.String,
java.lang.Short, java.lang.Integer, java.lang.Long,
java.lang.Double, java.math.BigDecimal
DATE, TIME, DATETIME, TIMESTAMP java.lang.String,
java.sql.Date, java.sql.Timestamp
Note
Round-off, overflow or loss of precision may occur if you
choose a Java numeric data type that has less precision or
capacity than the MySQL data type you are converting to/from.
The ResultSet.getObject() method uses the type conversions
between MySQL and Java types, following the JDBC
specification where appropriate. The value returned by
ResultSetMetaData.GetColumnClassName() is also shown below.
For more information on the JDBC types, see the reference on
the java.sql.Types
(http://docs.oracle.com/javase/8/docs/api/java/sql/Types.html
) class.
Table 5.2 MySQL Types to Java Types for ResultSet.getObject()
MySQL Type Name Return value of GetColumnClassName Returned
as Java Class
BIT(1) (new in MySQL-5.0) BIT java.lang.Boolean
BIT( > 1) (new in MySQL-5.0) BIT byte[]
TINYINT TINYINT java.lang.Boolean if the configuration
property tinyInt1isBit is set to true (the default) and the
storage size is 1, or java.lang.Integer if not.
BOOL, BOOLEAN TINYINT See TINYINT, above as these are aliases
for TINYINT(1), currently.
SMALLINT[(M)] [UNSIGNED] SMALLINT [UNSIGNED]
java.lang.Integer (regardless if UNSIGNED or not)
MEDIUMINT[(M)] [UNSIGNED] MEDIUMINT [UNSIGNED]
java.lang.Integer, if UNSIGNED java.lang.Long (C/J 3.1 and
earlier), or java.lang.Integer for C/J 5.0 and later
INT,INTEGER[(M)] [UNSIGNED] INTEGER [UNSIGNED]
java.lang.Integer, if UNSIGNED java.lang.Long
BIGINT[(M)] [UNSIGNED] BIGINT [UNSIGNED] java.lang.Long, if
UNSIGNED java.math.BigInteger
FLOAT[(M,D)] FLOAT java.lang.Float
DOUBLE[(M,B)] DOUBLE java.lang.Double
DECIMAL[(M[,D])] DECIMAL java.math.BigDecimal
DATE DATE java.sql.Date
DATETIME DATETIME java.sql.Timestamp
TIMESTAMP[(M)] TIMESTAMP java.sql.Timestamp
TIME TIME java.sql.Time
YEAR[(2|4)] YEAR If yearIsDateType configuration property is
set to false, then the returned object type is
java.sql.Short. If set to true (the default), then the
returned object is of type java.sql.Date with the date set to
January 1st, at midnight.
CHAR(M) CHAR java.lang.String (unless the character set for
the column is BINARY, then byte[] is returned.
VARCHAR(M) [BINARY] VARCHAR java.lang.String (unless the
character set for the column is BINARY, then byte[] is
returned.
BINARY(M) BINARY byte[]
VARBINARY(M) VARBINARY byte[]
TINYBLOB TINYBLOB byte[]
TINYTEXT VARCHAR java.lang.String
BLOB BLOB byte[]
TEXT VARCHAR java.lang.String
MEDIUMBLOB MEDIUMBLOB byte[]
MEDIUMTEXT VARCHAR java.lang.String
LONGBLOB LONGBLOB byte[]
LONGTEXT VARCHAR java.lang.String
ENUM('value1','value2',...) CHAR java.lang.String
SET('value1','value2',...) CHAR java.lang.String
5.4 Using Character Sets and Unicode
All strings sent from the JDBC driver to the server are
converted automatically from native Java Unicode form to the
client character encoding, including all queries sent using
Statement.execute(), Statement.executeUpdate(),
Statement.executeQuery() as well as all PreparedStatement and
CallableStatement parameters with the exclusion of parameters
set using setBytes(), setBinaryStream(), setAsciiStream(),
setUnicodeStream() and setBlob().
Number of Encodings Per Connection
In MySQL Server 4.1 and higher, Connector/J supports a single
character encoding between client and server, and any number
of character encodings for data returned by the server to the
client in ResultSets.
Prior to MySQL Server 4.1, Connector/J supported a single
character encoding per connection, which could either be
automatically detected from the server configuration, or
could be configured by the user through the useUnicode and
characterEncoding properties.
Setting the Character Encoding
The character encoding between client and server is
automatically detected upon connection. You specify the
encoding on the server using the character_set_server
(http://dev.mysql.com/doc/refman/5.7/en/server-system-variabl
es.html#sysvar_character_set_server) for server versions
4.1.0 and newer, and character_set system variable for server
versions older than 4.1.0. The driver automatically uses the
encoding specified by the server. For more information, see
Server Character Set and Collation
(http://dev.mysql.com/doc/refman/5.7/en/charset-server.html).
For example, to use 4-byte UTF-8 character sets with
Connector/J, configure the MySQL server with
character_set_server=utf8mb4
(http://dev.mysql.com/doc/refman/5.7/en/server-system-variabl
es.html#sysvar_character_set_server), and leave
characterEncoding out of the Connector/J connection string.
Connector/J will then autodetect the UTF-8 setting.
To override the automatically detected encoding on the client
side, use the characterEncoding property in the URL used to
connect to the server.
To allow multiple character sets to be sent from the client,
use the UTF-8 encoding, either by configuring utf8 as the
default server character set, or by configuring the JDBC
driver to use UTF-8 through the characterEncoding property.
When specifying character encodings on the client side, use
Java-style names. The following table lists MySQL character
set names and the corresponding Java-style names:
Table 5.3 MySQL to Java Encoding Name Translations
MySQL Character Set Name Java-Style Character Encoding Name
ascii US-ASCII
big5 Big5
gbk GBK
sjis SJIS (or Cp932 or MS932 for MySQL Server < 4.1.11)
cp932 Cp932 or MS932 (MySQL Server > 4.1.11)
gb2312 EUC_CN
ujis EUC_JP
euckr EUC_KR
latin1 Cp1252
latin2 ISO8859_2
greek ISO8859_7
hebrew ISO8859_8
cp866 Cp866
tis620 TIS620
cp1250 Cp1250
cp1251 Cp1251
cp1257 Cp1257
macroman MacRoman
macce MacCentralEurope
utf8 UTF-8
ucs2 UnicodeBig
Warning
Do not issue the query set names with Connector/J, as the
driver will not detect that the character set has changed,
and will continue to use the character set detected during
the initial connection setup.
5.5 Connecting Securely Using SSL
SSL in MySQL Connector/J encrypts all data (other than the
initial handshake) between the JDBC driver and the server.
There is a performance penalty for enabling SSL, the severity
of which depends on multiple factors including (but not
limited to) the size of the query, the amount of data
returned, the server hardware, the SSL library used, the
network bandwidth, and so on.
For SSL support to work, you must have the following:
* A JDK that includes JSSE (Java Secure Sockets Extension),
like JDK-1.4.1 or newer. SSL does not currently work with
a JDK that you can add JSSE to, like JDK-1.2.x or
JDK-1.3.x due to the following JSSE bug:
http://bugs.java.com/bugdatabase/view_bug.do?bug_id=42735
44
* A MySQL server that supports SSL and has been compiled
and configured to do so, which is MySQL 4.0.4 or later.
For more information, see Building MySQL with Support for
Secure Connections
(http://dev.mysql.com/doc/refman/5.7/en/building-with-sec
ure-connection-support.html).
* A client certificate (covered later in this section)
The system works through two Java truststore files, one file
contains the certificate information for the server
(truststore in the examples below). The other file contains
the certificate for the client (keystore in the examples
below). All Java truststore files are password protected by
supplying a suitable password to the keytool when you create
the files. You need the file names and associated passwords
to create an SSL connection.
You will first need to import the MySQL server CA Certificate
into a Java truststore. A sample MySQL server CA Certificate
is located in the SSL subdirectory of the MySQL source
distribution. This is what SSL will use to determine if you
are communicating with a secure MySQL server. Alternatively,
use the CA Certificate that you have generated or been
provided with by your SSL provider.
To use Java's keytool to create a truststore in the current
directory , and import the server's CA certificate
(cacert.pem), you can do the following (assuming that keytool
is in your path. The keytool is typically located in the bin
subdirectory of your JDK or JRE):
shell> keytool -import -alias mysqlServerCACert \
-file cacert.pem -keystore truststore
Enter the password when prompted for the keystore file.
Interaction with keytool looks like this:
Enter keystore password: *********
Owner: EMAILADDRESS=walrus@example.com, CN=Walrus,
O=My Company, L=Orenburg, ST=Some-State, C=RU
Issuer: EMAILADDRESS=walrus@example.com, CN=Walrus,
O=My Company, L=Orenburg, ST=Some-State, C=RU
Serial number: 0
Valid from:
Fri Aug 02 16:55:53 CDT 2002 until: Sat Aug 02 16:55:53 CDT 2003
Certificate fingerprints:
MD5: 61:91:A0:F2:03:07:61:7A:81:38:66:DA:19:C4:8D:AB
SHA1: 25:77:41:05:D5:AD:99:8C:14:8C:CA:68:9C:2F:B8:89:C3:34:4D:6C
Trust this certificate? [no]: yes
Certificate was added to keystore
You then have two options: either import the client
certificate that matches the CA certificate you just
imported, or create a new client certificate.
Importing an existing certificate requires the certificate to
be in DER format. You can use openssl to convert an existing
certificate into the new format. For example:
shell> openssl x509 -outform DER -in client-cert.pem -out client.cert
Now import the converted certificate into your keystore using
keytool:
shell> keytool -import -file client.cert -keystore keystore -alias mys
qlClientCertificate
To generate your own client certificate, use keytool to
create a suitable certificate and add it to the keystore
file:
shell> keytool -genkey -keyalg rsa \
-alias mysqlClientCertificate -keystore keystore
Keytool will prompt you for the following information, and
create a keystore named keystore in the current directory.
Respond with information that is appropriate for your
situation:
Enter keystore password: *********
What is your first and last name?
[Unknown]: Matthews
What is the name of your organizational unit?
[Unknown]: Software Development
What is the name of your organization?
[Unknown]: My Company
What is the name of your City or Locality?
[Unknown]: Flossmoor
What is the name of your State or Province?
[Unknown]: IL
What is the two-letter country code for this unit?
[Unknown]: US
Is <CN=Matthews, OU=Software Development, O=My Company,
L=Flossmoor, ST=IL, C=US> correct?
[no]: y
Enter key password for <mysqlClientCertificate>
(RETURN if same as keystore password):
Finally, to get JSSE to use the keystore and truststore that
you have generated, you need to set the following system
properties when you start your JVM, replacing
path_to_keystore_file with the full path to the keystore file
you created, path_to_truststore_file with the path to the
truststore file you created, and using the appropriate
password values for each property. You can do this either on
the command line:
-Djavax.net.ssl.keyStore=path_to_keystore_file
-Djavax.net.ssl.keyStorePassword=password
-Djavax.net.ssl.trustStore=path_to_truststore_file
-Djavax.net.ssl.trustStorePassword=password
Or you can set the values directly within the application:
System.setProperty("javax.net.ssl.keyStore","path_to_keystore_file");
System.setProperty("javax.net.ssl.keyStorePassword","password");
System.setProperty("javax.net.ssl.trustStore","path_to_truststore_file
");
System.setProperty("javax.net.ssl.trustStorePassword","password");
You will also need to set useSSL to true in your connection
parameters for MySQL Connector/J, either by adding
useSSL=true to your URL, or by setting the property useSSL to
true in the java.util.Properties instance you pass to
DriverManager.getConnection().
You can test that SSL is working by turning on JSSE debugging
(as detailed below), and look for the following key events:
...
*** ClientHello, v3.1
RandomCookie: GMT: 1018531834 bytes = { 199, 148, 180, 215, 74, 12,
??
54, 244, 0, 168, 55, 103, 215, 64, 16, 138, 225, 190, 132, 153, 2,
??
217, 219, 239, 202, 19, 121, 78 }
Session ID: {}
Cipher Suites: { 0, 5, 0, 4, 0, 9, 0, 10, 0, 18, 0, 19, 0, 3, 0, 17 }
Compression Methods: { 0 }
***
[write] MD5 and SHA1 hashes: len = 59
0000: 01 00 00 37 03 01 3D B6 90 FA C7 94 B4 D7 4A 0C ...7..=.......J
.
0010: 36 F4 00 A8 37 67 D7 40 10 8A E1 BE 84 99 02 D9 6...7g.@.......
.
0020: DB EF CA 13 79 4E 00 00 10 00 05 00 04 00 09 00 ....yN.........
.
0030: 0A 00 12 00 13 00 03 00 11 01 00 ...........
main, WRITE: SSL v3.1 Handshake, length = 59
main, READ: SSL v3.1 Handshake, length = 74
*** ServerHello, v3.1
RandomCookie: GMT: 1018577560 bytes = { 116, 50, 4, 103, 25, 100, 58,
??
202, 79, 185, 178, 100, 215, 66, 254, 21, 83, 187, 190, 42, 170, 3,
??
132, 110, 82, 148, 160, 92 }
Session ID: {163, 227, 84, 53, 81, 127, 252, 254, 178, 179, 68, 63,
??
182, 158, 30, 11, 150, 79, 170, 76, 255, 92, 15, 226, 24, 17, 177,
??
219, 158, 177, 187, 143}
Cipher Suite: { 0, 5 }
Compression Method: 0
***
%% Created: [Session-1, SSL_RSA_WITH_RC4_128_SHA]
** SSL_RSA_WITH_RC4_128_SHA
[read] MD5 and SHA1 hashes: len = 74
0000: 02 00 00 46 03 01 3D B6 43 98 74 32 04 67 19 64 ...F..=.C.t2.g.
d
0010: 3A CA 4F B9 B2 64 D7 42 FE 15 53 BB BE 2A AA 03 :.O..d.B..S..*.
.
0020: 84 6E 52 94 A0 5C 20 A3 E3 54 35 51 7F FC FE B2 .nR..\ ..T5Q...
.
0030: B3 44 3F B6 9E 1E 0B 96 4F AA 4C FF 5C 0F E2 18 .D?.....O.L.\..
.
0040: 11 B1 DB 9E B1 BB 8F 00 05 00 ..........
main, READ: SSL v3.1 Handshake, length = 1712
...
JSSE provides debugging (to stdout) when you set the
following system property: -Djavax.net.debug=all This will
tell you what keystores and truststores are being used, as
well as what is going on during the SSL handshake and
certificate exchange. It will be helpful when trying to
determine what is not working when trying to get an SSL
connection to happen.
5.6 Connecting Using PAM Authentication
Java applications using Connector/J 5.1.21 and higher can
connect to MySQL servers that use the pluggable
authentication module (PAM) authentication scheme.
For PAM authentication to work, you must have the following:
* A MySQL server that supports PAM authentication: a
commercial distribution of MySQL 5.5.16 or higher. See
The PAM Authentication Plugin
(http://dev.mysql.com/doc/refman/5.7/en/pam-authenticatio
n-plugin.html) for more information. Connector/J
implements the same cleartext authentication method as in
The Cleartext Client-Side Authentication Plugin
(http://dev.mysql.com/doc/refman/5.7/en/cleartext-authent
ication-plugin.html).
* SSL capability, as explained in Section 5.5, "Connecting
Securely Using SSL." Because the PAM authentication
scheme sends the original password to the server, the
connection to the server must be encrypted.
PAM authentication support is enabled by default in
Connector/J 5.1.21 and up, so no extra configuration is
needed.
To disable the PAM authentication feature, specify
mysql_clear_password (the method) or
com.mysql.jdbc.authentication.MysqlClearPasswordPlugin (the
class name) in the comma-separated list of arguments for the
disabledAuthenticationPlugins connection option. See Section
5.1, "Driver/Datasource Class Names, URL Syntax and
Configuration Properties for Connector/J" for details about
that connection option.
5.7 Using Master/Slave Replication with ReplicationConnection
See Section 8.3, "Configuring Master/Slave Replication with
Connector/J" for details on the topic.
5.8 Mapping MySQL Error Numbers to JDBC SQLState Codes
The table below provides a mapping of the MySQL error numbers
to JDBC SQLState values.
Table 5.4 Mapping of MySQL Error Numbers to SQLStates
MySQL Error Number MySQL Error Name Legacy (X/Open) SQLState
SQL Standard SQLState
1022 ER_DUP_KEY 23000 23000
1037 ER_OUTOFMEMORY S1001 HY001
1038 ER_OUT_OF_SORTMEMORY S1001 HY001
1040 ER_CON_COUNT_ERROR 08004 08004
1042 ER_BAD_HOST_ERROR 08004 08S01
1043 ER_HANDSHAKE_ERROR 08004 08S01
1044 ER_DBACCESS_DENIED_ERROR 42000 42000
1045 ER_ACCESS_DENIED_ERROR 28000 28000
1046 ER_NO_DB_ERROR 3D000 3D000
1047 ER_UNKNOWN_COM_ERROR 08S01 08S01
1048 ER_BAD_NULL_ERROR 23000 23000
1049 ER_BAD_DB_ERROR 42000 42000
1050 ER_TABLE_EXISTS_ERROR 42S01 42S01
1051 ER_BAD_TABLE_ERROR 42S02 42S02
1052 ER_NON_UNIQ_ERROR 23000 23000
1053 ER_SERVER_SHUTDOWN 08S01 08S01
1054 ER_BAD_FIELD_ERROR S0022 42S22
1055 ER_WRONG_FIELD_WITH_GROUP S1009 42000
1056 ER_WRONG_GROUP_FIELD S1009 42000
1057 ER_WRONG_SUM_SELECT S1009 42000
1058 ER_WRONG_VALUE_COUNT 21S01 21S01
1059 ER_TOO_LONG_IDENT S1009 42000
1060 ER_DUP_FIELDNAME S1009 42S21
1061 ER_DUP_KEYNAME S1009 42000
1062 ER_DUP_ENTRY S1009 23000
1063 ER_WRONG_FIELD_SPEC S1009 42000
1064 ER_PARSE_ERROR 42000 42000
1065 ER_EMPTY_QUERY 42000 42000
1066 ER_NONUNIQ_TABLE S1009 42000
1067 ER_INVALID_DEFAULT S1009 42000
1068 ER_MULTIPLE_PRI_KEY S1009 42000
1069 ER_TOO_MANY_KEYS S1009 42000
1070 ER_TOO_MANY_KEY_PARTS S1009 42000
1071 ER_TOO_LONG_KEY S1009 42000
1072 ER_KEY_COLUMN_DOES_NOT_EXITS S1009 42000
1073 ER_BLOB_USED_AS_KEY S1009 42000
1074 ER_TOO_BIG_FIELDLENGTH S1009 42000
1075 ER_WRONG_AUTO_KEY S1009 42000
1080 ER_FORCING_CLOSE 08S01 08S01
1081 ER_IPSOCK_ERROR 08S01 08S01
1082 ER_NO_SUCH_INDEX S1009 42S12
1083 ER_WRONG_FIELD_TERMINATORS S1009 42000
1084 ER_BLOBS_AND_NO_TERMINATED S1009 42000
1090 ER_CANT_REMOVE_ALL_FIELDS 42000 42000
1091 ER_CANT_DROP_FIELD_OR_KEY 42000 42000
1101 ER_BLOB_CANT_HAVE_DEFAULT 42000 42000
1102 ER_WRONG_DB_NAME 42000 42000
1103 ER_WRONG_TABLE_NAME 42000 42000
1104 ER_TOO_BIG_SELECT 42000 42000
1106 ER_UNKNOWN_PROCEDURE 42000 42000
1107 ER_WRONG_PARAMCOUNT_TO_PROCEDURE 42000 42000
1109 ER_UNKNOWN_TABLE 42S02 42S02
1110 ER_FIELD_SPECIFIED_TWICE 42000 42000
1112 ER_UNSUPPORTED_EXTENSION 42000 42000
1113 ER_TABLE_MUST_HAVE_COLUMNS 42000 42000
1115 ER_UNKNOWN_CHARACTER_SET 42000 42000
1118 ER_TOO_BIG_ROWSIZE 42000 42000
1120 ER_WRONG_OUTER_JOIN 42000 42000
1121 ER_NULL_COLUMN_IN_INDEX 42000 42000
1129 ER_HOST_IS_BLOCKED 08004 HY000
1130 ER_HOST_NOT_PRIVILEGED 08004 HY000
1131 ER_PASSWORD_ANONYMOUS_USER 42000 42000
1132 ER_PASSWORD_NOT_ALLOWED 42000 42000
1133 ER_PASSWORD_NO_MATCH 42000 42000
1136 ER_WRONG_VALUE_COUNT_ON_ROW 21S01 21S01
1138 ER_INVALID_USE_OF_NULL S1000 42000
1139 ER_REGEXP_ERROR 42000 42000
1140 ER_MIX_OF_GROUP_FUNC_AND_FIELDS 42000 42000
1141 ER_NONEXISTING_GRANT 42000 42000
1142 ER_TABLEACCESS_DENIED_ERROR 42000 42000
1143 ER_COLUMNACCESS_DENIED_ERROR 42000 42000
1144 ER_ILLEGAL_GRANT_FOR_TABLE 42000 42000
1145 ER_GRANT_WRONG_HOST_OR_USER 42000 42000
1146 ER_NO_SUCH_TABLE 42S02 42S02
1147 ER_NONEXISTING_TABLE_GRANT 42000 42000
1148 ER_NOT_ALLOWED_COMMAND 42000 42000
1149 ER_SYNTAX_ERROR 42000 42000
1152 ER_ABORTING_CONNECTION 08S01 08S01
1153 ER_NET_PACKET_TOO_LARGE 08S01 08S01
1154 ER_NET_READ_ERROR_FROM_PIPE 08S01 08S01
1155 ER_NET_FCNTL_ERROR 08S01 08S01
1156 ER_NET_PACKETS_OUT_OF_ORDER 08S01 08S01
1157 ER_NET_UNCOMPRESS_ERROR 08S01 08S01
1158 ER_NET_READ_ERROR 08S01 08S01
1159 ER_NET_READ_INTERRUPTED 08S01 08S01
1160 ER_NET_ERROR_ON_WRITE 08S01 08S01
1161 ER_NET_WRITE_INTERRUPTED 08S01 08S01
1162 ER_TOO_LONG_STRING 42000 42000
1163 ER_TABLE_CANT_HANDLE_BLOB 42000 42000
1164 ER_TABLE_CANT_HANDLE_AUTO_INCREMENT 42000 42000
1166 ER_WRONG_COLUMN_NAME 42000 42000
1167 ER_WRONG_KEY_COLUMN 42000 42000
1169 ER_DUP_UNIQUE 23000 23000
1170 ER_BLOB_KEY_WITHOUT_LENGTH 42000 42000
1171 ER_PRIMARY_CANT_HAVE_NULL 42000 42000
1172 ER_TOO_MANY_ROWS 42000 42000
1173 ER_REQUIRES_PRIMARY_KEY 42000 42000
1176 ER_KEY_DOES_NOT_EXITS 42000 42000
1177 ER_CHECK_NO_SUCH_TABLE 42000 42000
1178 ER_CHECK_NOT_IMPLEMENTED 42000 42000
1179 ER_CANT_DO_THIS_DURING_AN_TRANSACTION 25000 25000
1184 ER_NEW_ABORTING_CONNECTION 08S01 08S01
1189 ER_MASTER_NET_READ 08S01 08S01
1190 ER_MASTER_NET_WRITE 08S01 08S01
1203 ER_TOO_MANY_USER_CONNECTIONS 42000 42000
1205 ER_LOCK_WAIT_TIMEOUT 40001 40001
1207 ER_READ_ONLY_TRANSACTION 25000 25000
1211 ER_NO_PERMISSION_TO_CREATE_USER 42000 42000
1213 ER_LOCK_DEADLOCK 40001 40001
1216 ER_NO_REFERENCED_ROW 23000 23000
1217 ER_ROW_IS_REFERENCED 23000 23000
1218 ER_CONNECT_TO_MASTER 08S01 08S01
1222 ER_WRONG_NUMBER_OF_COLUMNS_IN_SELECT 21000 21000
1226 ER_USER_LIMIT_REACHED 42000 42000
1227 ER_SPECIFIC_ACCESS_DENIED_ERROR 42000 42000
1230 ER_NO_DEFAULT 42000 42000
1231 ER_WRONG_VALUE_FOR_VAR 42000 42000
1232 ER_WRONG_TYPE_FOR_VAR 42000 42000
1234 ER_CANT_USE_OPTION_HERE 42000 42000
1235 ER_NOT_SUPPORTED_YET 42000 42000
1239 ER_WRONG_FK_DEF 42000 42000
1241 ER_OPERAND_COLUMNS 21000 21000
1242 ER_SUBQUERY_NO_1_ROW 21000 21000
1247 ER_ILLEGAL_REFERENCE 42S22 42S22
1248 ER_DERIVED_MUST_HAVE_ALIAS 42000 42000
1249 ER_SELECT_REDUCED 01000 01000
1250 ER_TABLENAME_NOT_ALLOWED_HERE 42000 42000
1251 ER_NOT_SUPPORTED_AUTH_MODE 08004 08004
1252 ER_SPATIAL_CANT_HAVE_NULL 42000 42000
1253 ER_COLLATION_CHARSET_MISMATCH 42000 42000
1261 ER_WARN_TOO_FEW_RECORDS 01000 01000
1262 ER_WARN_TOO_MANY_RECORDS 01000 01000
1263 ER_WARN_NULL_TO_NOTNULL S1000 01000
1264 ER_WARN_DATA_OUT_OF_RANGE 01000 01000
1265 ER_WARN_DATA_TRUNCATED 01000 01000
1280 ER_WRONG_NAME_FOR_INDEX 42000 42000
1281 ER_WRONG_NAME_FOR_CATALOG 42000 42000
1286 ER_UNKNOWN_STORAGE_ENGINE 42000 42000
1292 ER_TRUNCATED_WRONG_VALUE 22007 22007
1303 ER_SP_NO_RECURSIVE_CREATE S1000 2F003
1304 ER_SP_ALREADY_EXISTS 42000 42000
1305 ER_SP_DOES_NOT_EXIST 42000 42000
1308 ER_SP_LILABEL_MISMATCH 42000 42000
1309 ER_SP_LABEL_REDEFINE 42000 42000
1310 ER_SP_LABEL_MISMATCH 42000 42000
1311 ER_SP_UNINIT_VAR 01000 01000
1312 ER_SP_BADSELECT 0A000 0A000
1313 ER_SP_BADRETURN 42000 42000
1314 ER_SP_BADSTATEMENT 0A000 0A000
1315 ER_UPDATE_LOG_DEPRECATED_IGNORED 42000 42000
1316 ER_UPDATE_LOG_DEPRECATED_TRANSLATED 42000 42000
1317 ER_QUERY_INTERRUPTED S1000 70100
1318 ER_SP_WRONG_NO_OF_ARGS 42000 42000
1319 ER_SP_COND_MISMATCH 42000 42000
1320 ER_SP_NORETURN 42000 42000
1321 ER_SP_NORETURNEND S1000 2F005
1322 ER_SP_BAD_CURSOR_QUERY 42000 42000
1323 ER_SP_BAD_CURSOR_SELECT 42000 42000
1324 ER_SP_CURSOR_MISMATCH 42000 42000
1325 ER_SP_CURSOR_ALREADY_OPEN 24000 24000
1326 ER_SP_CURSOR_NOT_OPEN 24000 24000
1327 ER_SP_UNDECLARED_VAR 42000 42000
1329 ER_SP_FETCH_NO_DATA S1000 02000
1330 ER_SP_DUP_PARAM 42000 42000
1331 ER_SP_DUP_VAR 42000 42000
1332 ER_SP_DUP_COND 42000 42000
1333 ER_SP_DUP_CURS 42000 42000
1335 ER_SP_SUBSELECT_NYI 0A000 0A000
1336 ER_STMT_NOT_ALLOWED_IN_SF_OR_TRG 0A000 0A000
1337 ER_SP_VARCOND_AFTER_CURSHNDLR 42000 42000
1338 ER_SP_CURSOR_AFTER_HANDLER 42000 42000
1339 ER_SP_CASE_NOT_FOUND S1000 20000
1365 ER_DIVISION_BY_ZERO 22012 22012
1367 ER_ILLEGAL_VALUE_FOR_TYPE 22007 22007
1370 ER_PROCACCESS_DENIED_ERROR 42000 42000
1397 ER_XAER_NOTA S1000 XAE04
1398 ER_XAER_INVAL S1000 XAE05
1399 ER_XAER_RMFAIL S1000 XAE07
1400 ER_XAER_OUTSIDE S1000 XAE09
1401 ER_XA_RMERR S1000 XAE03
1402 ER_XA_RBROLLBACK S1000 XA100
1403 ER_NONEXISTING_PROC_GRANT 42000 42000
1406 ER_DATA_TOO_LONG 22001 22001
1407 ER_SP_BAD_SQLSTATE 42000 42000
1410 ER_CANT_CREATE_USER_WITH_GRANT 42000 42000
1413 ER_SP_DUP_HANDLER 42000 42000
1414 ER_SP_NOT_VAR_ARG 42000 42000
1415 ER_SP_NO_RETSET 0A000 0A000
1416 ER_CANT_CREATE_GEOMETRY_OBJECT 22003 22003
1425 ER_TOO_BIG_SCALE 42000 42000
1426 ER_TOO_BIG_PRECISION 42000 42000
1427 ER_M_BIGGER_THAN_D 42000 42000
1437 ER_TOO_LONG_BODY 42000 42000
1439 ER_TOO_BIG_DISPLAYWIDTH 42000 42000
1440 ER_XAER_DUPID S1000 XAE08
1441 ER_DATETIME_FUNCTION_OVERFLOW 22008 22008
1451 ER_ROW_IS_REFERENCED_2 23000 23000
1452 ER_NO_REFERENCED_ROW_2 23000 23000
1453 ER_SP_BAD_VAR_SHADOW 42000 42000
1458 ER_SP_WRONG_NAME 42000 42000
1460 ER_SP_NO_AGGREGATE 42000 42000
1461 ER_MAX_PREPARED_STMT_COUNT_REACHED 42000 42000
1463 ER_NON_GROUPING_FIELD_USED 42000 42000
1557 ER_FOREIGN_DUPLICATE_KEY 23000 23000
1568 ER_CANT_CHANGE_TX_ISOLATION S1000 25001
1582 ER_WRONG_PARAMCOUNT_TO_NATIVE_FCT 42000 42000
1583 ER_WRONG_PARAMETERS_TO_NATIVE_FCT 42000 42000
1584 ER_WRONG_PARAMETERS_TO_STORED_FCT 42000 42000
1586 ER_DUP_ENTRY_WITH_KEY_NAME 23000 23000
1613 ER_XA_RBTIMEOUT S1000 XA106
1614 ER_XA_RBDEADLOCK S1000 XA102
1630 ER_FUNC_INEXISTENT_NAME_COLLISION 42000 42000
1641 ER_DUP_SIGNAL_SET 42000 42000
1642 ER_SIGNAL_WARN 01000 01000
1643 ER_SIGNAL_NOT_FOUND S1000 02000
1645 ER_RESIGNAL_WITHOUT_ACTIVE_HANDLER S1000 0K000
1687 ER_SPATIAL_MUST_HAVE_GEOM_COL 42000 42000
1690 ER_DATA_OUT_OF_RANGE 22003 22003
1698 ER_ACCESS_DENIED_NO_PASSWORD_ERROR 28000 28000
1701 ER_TRUNCATE_ILLEGAL_FK 42000 42000
1758 ER_DA_INVALID_CONDITION_NUMBER 35000 35000
1761 ER_FOREIGN_DUPLICATE_KEY_WITH_CHILD_INFO 23000 23000
1762 ER_FOREIGN_DUPLICATE_KEY_WITHOUT_CHILD_INFO 23000 23000
1792 ER_CANT_EXECUTE_IN_READ_ONLY_TRANSACTION S1000 25006
1845 ER_ALTER_OPERATION_NOT_SUPPORTED 0A000 0A000
1846 ER_ALTER_OPERATION_NOT_SUPPORTED_REASON 0A000 0A000
1859 ER_DUP_UNKNOWN_IN_INDEX 23000 23000
1873 ER_ACCESS_DENIED_CHANGE_USER_ERROR 28000 28000
1887 ER_GET_STACKED_DA_WITHOUT_ACTIVE_HANDLER S1000 0Z002
1903 ER_INVALID_ARGUMENT_FOR_LOGARITHM S1000 2201E
Chapter 6 JDBC Concepts
This section provides some general JDBC background.
6.1 Connecting to MySQL Using the JDBC DriverManager Interface
When you are using JDBC outside of an application server, the
DriverManager class manages the establishment of connections.
Specify to the DriverManager which JDBC drivers to try to
make Connections with. The easiest way to do this is to use
Class.forName() on the class that implements the
java.sql.Driver interface. With MySQL Connector/J, the name
of this class is com.mysql.jdbc.Driver. With this method, you
could use an external configuration file to supply the driver
class name and driver parameters to use when connecting to a
database.
The following section of Java code shows how you might
register MySQL Connector/J from the main() method of your
application. If testing this code, first read the
installation section at Chapter 3, "Connector/J
Installation," to make sure you have connector installed
correctly and the CLASSPATH set up. Also, ensure that MySQL
is configured to accept external TCP/IP connections.
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
// Notice, do not import com.mysql.jdbc.*
// or you will have problems!
public class LoadDriver {
public static void main(String[] args) {
try {
// The newInstance() call is a work around for some
// broken Java implementations
Class.forName("com.mysql.jdbc.Driver").newInstance();
} catch (Exception ex) {
// handle the error
}
}
}
After the driver has been registered with the DriverManager,
you can obtain a Connection instance that is connected to a
particular database by calling DriverManager.getConnection():
Example 6.1 Connector/J: Obtaining a connection from the
DriverManager
If you have not already done so, please review the portion of
Section 6.1, "Connecting to MySQL Using the JDBC
DriverManager Interface" above before working with the
example below.
This example shows how you can obtain a Connection instance
from the DriverManager. There are a few different signatures
for the getConnection() method. Consult the API documentation
that comes with your JDK for more specific information on how
to use them.
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
Connection conn = null;
...
try {
conn =
DriverManager.getConnection("jdbc:mysql://localhost/test?" +
"user=minty&password=greatsqldb");
// Do something with the Connection
...
} catch (SQLException ex) {
// handle any errors
System.out.println("SQLException: " + ex.getMessage());
System.out.println("SQLState: " + ex.getSQLState());
System.out.println("VendorError: " + ex.getErrorCode());
}
Once a Connection is established, it can be used to create
Statement and PreparedStatement objects, as well as retrieve
metadata about the database. This is explained in the
following sections.
6.2 Using JDBC Statement Objects to Execute SQL
Statement objects allow you to execute basic SQL queries and
retrieve the results through the ResultSet class, which is
described later.
To create a Statement instance, you call the
createStatement() method on the Connection object you have
retrieved using one of the DriverManager.getConnection() or
DataSource.getConnection() methods described earlier.
Once you have a Statement instance, you can execute a SELECT
(http://dev.mysql.com/doc/refman/5.7/en/select.html) query by
calling the executeQuery(String) method with the SQL you want
to use.
To update data in the database, use the executeUpdate(String
SQL) method. This method returns the number of rows matched
by the update statement, not the number of rows that were
modified.
If you do not know ahead of time whether the SQL statement
will be a SELECT
(http://dev.mysql.com/doc/refman/5.7/en/select.html) or an
UPDATE
(http://dev.mysql.com/doc/refman/5.7/en/update.html)/INSERT
(http://dev.mysql.com/doc/refman/5.7/en/insert.html), then
you can use the execute(String SQL) method. This method will
return true if the SQL query was a SELECT
(http://dev.mysql.com/doc/refman/5.7/en/select.html), or
false if it was an UPDATE
(http://dev.mysql.com/doc/refman/5.7/en/update.html), INSERT
(http://dev.mysql.com/doc/refman/5.7/en/insert.html), or
DELETE (http://dev.mysql.com/doc/refman/5.7/en/delete.html)
statement. If the statement was a SELECT
(http://dev.mysql.com/doc/refman/5.7/en/select.html) query,
you can retrieve the results by calling the getResultSet()
method. If the statement was an UPDATE
(http://dev.mysql.com/doc/refman/5.7/en/update.html), INSERT
(http://dev.mysql.com/doc/refman/5.7/en/insert.html), or
DELETE (http://dev.mysql.com/doc/refman/5.7/en/delete.html)
statement, you can retrieve the affected rows count by
calling getUpdateCount() on the Statement instance.
Example 6.2 Connector/J: Using java.sql.Statement to execute
a SELECT query
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
import java.sql.ResultSet;
// assume that conn is an already created JDBC connection (see previou
s examples)
Statement stmt = null;
ResultSet rs = null;
try {
stmt = conn.createStatement();
rs = stmt.executeQuery("SELECT foo FROM bar");
// or alternatively, if you don't know ahead of time that
// the query will be a SELECT...
if (stmt.execute("SELECT foo FROM bar")) {
rs = stmt.getResultSet();
}
// Now do something with the ResultSet ....
}
catch (SQLException ex){
// handle any errors
System.out.println("SQLException: " + ex.getMessage());
System.out.println("SQLState: " + ex.getSQLState());
System.out.println("VendorError: " + ex.getErrorCode());
}
finally {
// it is a good idea to release
// resources in a finally{} block
// in reverse-order of their creation
// if they are no-longer needed
if (rs != null) {
try {
rs.close();
} catch (SQLException sqlEx) { } // ignore
rs = null;
}
if (stmt != null) {
try {
stmt.close();
} catch (SQLException sqlEx) { } // ignore
stmt = null;
}
}
6.3 Using JDBC CallableStatements to Execute Stored Procedures
Starting with MySQL server version 5.0 when used with
Connector/J 3.1.1 or newer, the java.sql.CallableStatement
interface is fully implemented with the exception of the
getParameterMetaData() method.
For more information on MySQL stored procedures, please refer
to Using Stored Routines (Procedures and Functions)
(http://dev.mysql.com/doc/refman/5.7/en/stored-routines.html)
.
Connector/J exposes stored procedure functionality through
JDBC's CallableStatement interface.
Note
Current versions of MySQL server do not return enough
information for the JDBC driver to provide result set
metadata for callable statements. This means that when using
CallableStatement, ResultSetMetaData may return NULL.
The following example shows a stored procedure that returns
the value of inOutParam incremented by 1, and the string
passed in using inputParam as a ResultSet:
Example 6.3 Connector/J: Calling Stored Procedures
CREATE PROCEDURE demoSp(IN inputParam VARCHAR(255), \
INOUT inOutParam INT)
BEGIN
DECLARE z INT;
SET z = inOutParam + 1;
SET inOutParam = z;
SELECT inputParam;
SELECT CONCAT('zyxw', inputParam);
END
To use the demoSp procedure with Connector/J, follow these
steps:
1. Prepare the callable statement by using
Connection.prepareCall().
Notice that you have to use JDBC escape syntax, and that
the parentheses surrounding the parameter placeholders
are not optional:
Example 6.4 Connector/J: Using Connection.prepareCall()
import java.sql.CallableStatement;
...
//
// Prepare a call to the stored procedure 'demoSp'
// with two parameters
//
// Notice the use of JDBC-escape syntax ({call ...})
//
CallableStatement cStmt = conn.prepareCall("{call demoSp(?, ?)}");
cStmt.setString(1, "abcdefg");
Note
Connection.prepareCall() is an expensive method, due to
the metadata retrieval that the driver performs to
support output parameters. For performance reasons,
minimize unnecessary calls to Connection.prepareCall() by
reusing CallableStatement instances in your code.
2. Register the output parameters (if any exist)
To retrieve the values of output parameters (parameters
specified as OUT or INOUT when you created the stored
procedure), JDBC requires that they be specified before
statement execution using the various
registerOutputParameter() methods in the
CallableStatement interface:
Example 6.5 Connector/J: Registering output parameters
import java.sql.Types;
...
//
// Connector/J supports both named and indexed
// output parameters. You can register output
// parameters using either method, as well
// as retrieve output parameters using either
// method, regardless of what method was
// used to register them.
//
// The following examples show how to use
// the various methods of registering
// output parameters (you should of course
// use only one registration per parameter).
//
//
// Registers the second parameter as output, and
// uses the type 'INTEGER' for values returned from
// getObject()
//
cStmt.registerOutParameter(2, Types.INTEGER);
//
// Registers the named parameter 'inOutParam', and
// uses the type 'INTEGER' for values returned from
// getObject()
//
cStmt.registerOutParameter("inOutParam", Types.INTEGER);
...
3. Set the input parameters (if any exist)
Input and in/out parameters are set as for
PreparedStatement objects. However, CallableStatement
also supports setting parameters by name:
Example 6.6 Connector/J: Setting CallableStatement input
parameters
...
//
// Set a parameter by index
//
cStmt.setString(1, "abcdefg");
//
// Alternatively, set a parameter using
// the parameter name
//
cStmt.setString("inputParameter", "abcdefg");
//
// Set the 'in/out' parameter using an index
//
cStmt.setInt(2, 1);
//
// Alternatively, set the 'in/out' parameter
// by name
//
cStmt.setInt("inOutParam", 1);
...
4. Execute the CallableStatement, and retrieve any result
sets or output parameters.
Although CallableStatement supports calling any of the
Statement execute methods (executeUpdate(),
executeQuery() or execute()), the most flexible method to
call is execute(), as you do not need to know ahead of
time if the stored procedure returns result sets:
Example 6.7 Connector/J: Retrieving results and output
parameter values
...
boolean hadResults = cStmt.execute();
//
// Process all returned result sets
//
while (hadResults) {
ResultSet rs = cStmt.getResultSet();
// process result set
...
hadResults = cStmt.getMoreResults();
}
//
// Retrieve output parameters
//
// Connector/J supports both index-based and
// name-based retrieval
//
int outputValue = cStmt.getInt(2); // index-based
outputValue = cStmt.getInt("inOutParam"); // name-based
...
6.4 Retrieving AUTO_INCREMENT Column Values through JDBC
Before version 3.0 of the JDBC API, there was no standard way
of retrieving key values from databases that supported auto
increment or identity columns. With older JDBC drivers for
MySQL, you could always use a MySQL-specific method on the
Statement interface, or issue the query SELECT
LAST_INSERT_ID() after issuing an INSERT
(http://dev.mysql.com/doc/refman/5.7/en/insert.html) to a
table that had an AUTO_INCREMENT key. Using the
MySQL-specific method call isn't portable, and issuing a
SELECT (http://dev.mysql.com/doc/refman/5.7/en/select.html)
to get the AUTO_INCREMENT key's value requires another
round-trip to the database, which isn't as efficient as
possible. The following code snippets demonstrate the three
different ways to retrieve AUTO_INCREMENT values. First, we
demonstrate the use of the new JDBC 3.0 method
getGeneratedKeys() which is now the preferred method to use
if you need to retrieve AUTO_INCREMENT keys and have access
to JDBC 3.0. The second example shows how you can retrieve
the same value using a standard SELECT LAST_INSERT_ID()
query. The final example shows how updatable result sets can
retrieve the AUTO_INCREMENT value when using the insertRow()
method.
Example 6.8 Connector/J: Retrieving AUTO_INCREMENT column
values using Statement.getGeneratedKeys()
Statement stmt = null;
ResultSet rs = null;
try {
//
// Create a Statement instance that we can use for
// 'normal' result sets assuming you have a
// Connection 'conn' to a MySQL database already
// available
stmt = conn.createStatement();
//
// Issue the DDL queries for the table for this example
//
stmt.executeUpdate("DROP TABLE IF EXISTS autoIncTutorial");
stmt.executeUpdate(
"CREATE TABLE autoIncTutorial ("
+ "priKey INT NOT NULL AUTO_INCREMENT, "
+ "dataField VARCHAR(64), PRIMARY KEY (priKey))");
//
// Insert one row that will generate an AUTO INCREMENT
// key in the 'priKey' field
//
stmt.executeUpdate(
"INSERT INTO autoIncTutorial (dataField) "
+ "values ('Can I Get the Auto Increment Field?')",
Statement.RETURN_GENERATED_KEYS);
//
// Example of using Statement.getGeneratedKeys()
// to retrieve the value of an auto-increment
// value
//
int autoIncKeyFromApi = -1;
rs = stmt.getGeneratedKeys();
if (rs.next()) {
autoIncKeyFromApi = rs.getInt(1);
} else {
// throw an exception from here
}
System.out.println("Key returned from getGeneratedKeys():"
+ autoIncKeyFromApi);
} finally {
if (rs != null) {
try {
rs.close();
} catch (SQLException ex) {
// ignore
}
}
if (stmt != null) {
try {
stmt.close();
} catch (SQLException ex) {
// ignore
}
}
}
Example 6.9 Connector/J: Retrieving AUTO_INCREMENT column
values using SELECT LAST_INSERT_ID()
Statement stmt = null;
ResultSet rs = null;
try {
//
// Create a Statement instance that we can use for
// 'normal' result sets.
stmt = conn.createStatement();
//
// Issue the DDL queries for the table for this example
//
stmt.executeUpdate("DROP TABLE IF EXISTS autoIncTutorial");
stmt.executeUpdate(
"CREATE TABLE autoIncTutorial ("
+ "priKey INT NOT NULL AUTO_INCREMENT, "
+ "dataField VARCHAR(64), PRIMARY KEY (priKey))");
//
// Insert one row that will generate an AUTO INCREMENT
// key in the 'priKey' field
//
stmt.executeUpdate(
"INSERT INTO autoIncTutorial (dataField) "
+ "values ('Can I Get the Auto Increment Field?')");
//
// Use the MySQL LAST_INSERT_ID()
// function to do the same thing as getGeneratedKeys()
//
int autoIncKeyFromFunc = -1;
rs = stmt.executeQuery("SELECT LAST_INSERT_ID()");
if (rs.next()) {
autoIncKeyFromFunc = rs.getInt(1);
} else {
// throw an exception from here
}
System.out.println("Key returned from " +
"'SELECT LAST_INSERT_ID()': " +
autoIncKeyFromFunc);
} finally {
if (rs != null) {
try {
rs.close();
} catch (SQLException ex) {
// ignore
}
}
if (stmt != null) {
try {
stmt.close();
} catch (SQLException ex) {
// ignore
}
}
}
Example 6.10 Connector/J: Retrieving AUTO_INCREMENT column
values in Updatable ResultSets
Statement stmt = null;
ResultSet rs = null;
try {
//
// Create a Statement instance that we can use for
// 'normal' result sets as well as an 'updatable'
// one, assuming you have a Connection 'conn' to
// a MySQL database already available
//
stmt = conn.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY,
java.sql.ResultSet.CONCUR_UPDATABLE);
//
// Issue the DDL queries for the table for this example
//
stmt.executeUpdate("DROP TABLE IF EXISTS autoIncTutorial");
stmt.executeUpdate(
"CREATE TABLE autoIncTutorial ("
+ "priKey INT NOT NULL AUTO_INCREMENT, "
+ "dataField VARCHAR(64), PRIMARY KEY (priKey))");
//
// Example of retrieving an AUTO INCREMENT key
// from an updatable result set
//
rs = stmt.executeQuery("SELECT priKey, dataField "
+ "FROM autoIncTutorial");
rs.moveToInsertRow();
rs.updateString("dataField", "AUTO INCREMENT here?");
rs.insertRow();
//
// the driver adds rows at the end
//
rs.last();
//
// We should now be on the row we just inserted
//
int autoIncKeyFromRS = rs.getInt("priKey");
System.out.println("Key returned for inserted row: "
+ autoIncKeyFromRS);
} finally {
if (rs != null) {
try {
rs.close();
} catch (SQLException ex) {
// ignore
}
}
if (stmt != null) {
try {
stmt.close();
} catch (SQLException ex) {
// ignore
}
}
}
Running the preceding example code should produce the
following output:
Key returned from getGeneratedKeys(): 1
Key returned from SELECT LAST_INSERT_ID(): 1
Key returned for inserted row: 1
At times, it can be tricky to use the SELECT LAST_INSERT_ID()
query, as that function's value is scoped to a connection.
So, if some other query happens on the same connection, the
value is overwritten. On the other hand, the
getGeneratedKeys() method is scoped by the Statement
instance, so it can be used even if other queries happen on
the same connection, but not on the same Statement instance.
Chapter 7 Connection Pooling with Connector/J
Connection pooling is a technique of creating and managing a
pool of connections that are ready for use by any thread
(http://dev.mysql.com/doc/refman/5.7/en/glossary.html#glos_th
read) that needs them. Connection pooling can greatly
increase the performance of your Java application, while
reducing overall resource usage.
How Connection Pooling Works
Most applications only need a thread to have access to a JDBC
connection when they are actively processing a transaction
(http://dev.mysql.com/doc/refman/5.7/en/glossary.html#glos_tr
ansaction), which often takes only milliseconds to complete.
When not processing a transaction, the connection sits idle.
Connection pooling enables the idle connection to be used by
some other thread to do useful work.
In practice, when a thread needs to do work against a MySQL
or other database with JDBC, it requests a connection from
the pool. When the thread is finished using the connection,
it returns it to the pool, so that it can be used by any
other threads.
When the connection is loaned out from the pool, it is used
exclusively by the thread that requested it. From a
programming point of view, it is the same as if your thread
called DriverManager.getConnection() every time it needed a
JDBC connection. With connection pooling, your thread may end
up using either a new connection or an already-existing
connection.
Benefits of Connection Pooling
The main benefits to connection pooling are:
* Reduced connection creation time.
Although this is not usually an issue with the quick
connection setup that MySQL offers compared to other
databases, creating new JDBC connections still incurs
networking and JDBC driver overhead that will be avoided
if connections are recycled.
* Simplified programming model.
When using connection pooling, each individual thread can
act as though it has created its own JDBC connection,
allowing you to use straightforward JDBC programming
techniques.
* Controlled resource usage.
If you create a new connection every time a thread needs
one rather than using connection pooling, your
application's resource usage can be wasteful, and it
could lead to unpredictable behaviors for your
application when it is under a heavy load.
Using Connection Pooling with Connector/J
The concept of connection pooling in JDBC has been
standardized through the JDBC 2.0 Optional interfaces, and
all major application servers have implementations of these
APIs that work with MySQL Connector/J.
Generally, you configure a connection pool in your
application server configuration files, and access it through
the Java Naming and Directory Interface (JNDI). The following
code shows how you might use a connection pool from an
application deployed in a J2EE application server:
Example 7.1 Connector/J: Using a connection pool with a J2EE
application server
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;
import javax.naming.InitialContext;
import javax.sql.DataSource;
public class MyServletJspOrEjb {
public void doSomething() throws Exception {
/*
* Create a JNDI Initial context to be able to
* lookup the DataSource
*
* In production-level code, this should be cached as
* an instance or static variable, as it can
* be quite expensive to create a JNDI context.
*
* Note: This code only works when you are using servlets
* or EJBs in a J2EE application server. If you are
* using connection pooling in standalone Java code, you
* will have to create/configure datasources using whatever
* mechanisms your particular connection pooling library
* provides.
*/
InitialContext ctx = new InitialContext();
/*
* Lookup the DataSource, which will be backed by a pool
* that the application server provides. DataSource instances
* are also a good candidate for caching as an instance
* variable, as JNDI lookups can be expensive as well.
*/
DataSource ds =
(DataSource)ctx.lookup("java:comp/env/jdbc/MySQLDB");
/*
* The following code is what would actually be in your
* Servlet, JSP or EJB 'service' method...where you need
* to work with a JDBC connection.
*/
Connection conn = null;
Statement stmt = null;
try {
conn = ds.getConnection();
/*
* Now, use normal JDBC programming to work with
* MySQL, making sure to close each resource when you're
* finished with it, which permits the connection pool
* resources to be recovered as quickly as possible
*/
stmt = conn.createStatement();
stmt.execute("SOME SQL QUERY");
stmt.close();
stmt = null;
conn.close();
conn = null;
} finally {
/*
* close any jdbc instances here that weren't
* explicitly closed during normal code path, so
* that we don't 'leak' resources...
*/
if (stmt != null) {
try {
stmt.close();
} catch (sqlexception sqlex) {
// ignore, as we can't do anything about it here
}
stmt = null;
}
if (conn != null) {
try {
conn.close();
} catch (sqlexception sqlex) {
// ignore, as we can't do anything about it here
}
conn = null;
}
}
}
}
As shown in the example above, after obtaining the JNDI
InitialContext, and looking up the DataSource, the rest of
the code follows familiar JDBC conventions.
When using connection pooling, always make sure that
connections, and anything created by them (such as statements
or result sets) are closed. This rule applies no matter what
happens in your code (exceptions, flow-of-control, and so
forth). When these objects are closed, they can be re-used;
otherwise, they will be stranded, which means that the MySQL
server resources they represent (such as buffers, locks, or
sockets) are tied up for some time, or in the worst case can
be tied up forever.
Sizing the Connection Pool
Each connection to MySQL has overhead (memory, CPU, context
switches, and so forth) on both the client and server side.
Every connection limits how many resources there are
available to your application as well as the MySQL server.
Many of these resources will be used whether or not the
connection is actually doing any useful work! Connection
pools can be tuned to maximize performance, while keeping
resource utilization below the point where your application
will start to fail rather than just run slower.
The optimal size for the connection pool depends on
anticipated load and average database transaction time. In
practice, the optimal connection pool size can be smaller
than you might expect. If you take Oracle's Java Petstore
blueprint application for example, a connection pool of 15-20
connections can serve a relatively moderate load (600
concurrent users) using MySQL and Tomcat with acceptable
response times.
To correctly size a connection pool for your application,
create load test scripts with tools such as Apache JMeter or
The Grinder, and load test your application.
An easy way to determine a starting point is to configure
your connection pool's maximum number of connections to be
unbounded, run a load test, and measure the largest amount of
concurrently used connections. You can then work backward
from there to determine what values of minimum and maximum
pooled connections give the best performance for your
particular application.
Validating Connections
MySQL Connector/J can validate the connection by executing a
lightweight ping against a server. In the case of
load-balanced connections, this is performed against all
active pooled internal connections that are retained. This is
beneficial to Java applications using connection pools, as
the pool can use this feature to validate connections.
Depending on your connection pool and configuration, this
validation can be carried out at different times:
1. Before the pool returns a connection to the application.
2. When the application returns a connection to the pool.
3. During periodic checks of idle connections.
To use this feature, specify a validation query in your
connection pool that starts with /* ping */. Note that the
syntax must be exactly as specified. This will cause the
driver send a ping to the server and return a dummy
lightweight result set. When using a ReplicationConnection or
LoadBalancedConnection, the ping will be sent across all
active connections.
It is critical that the syntax be specified correctly. The
syntax needs to be exact for reasons of efficiency, as this
test is done for every statement that is executed:
protected static final String PING_MARKER = "/* ping */";
...
if (sql.charAt(0) == '/') {
if (sql.startsWith(PING_MARKER)) {
doPingInstead();
...
None of the following snippets will work, because the ping
syntax is sensitive to whitespace, capitalization, and
placement:
sql = "/* PING */ SELECT 1";
sql = "SELECT 1 /* ping*/";
sql = "/*ping*/ SELECT 1";
sql = " /* ping */ SELECT 1";
sql = "/*to ping or not to ping*/ SELECT 1";
All of the previous statements will issue a normal SELECT
statement and will not be transformed into the lightweight
ping. Further, for load-balanced connections, the statement
will be executed against one connection in the internal pool,
rather than validating each underlying physical connection.
This results in the non-active physical connections assuming
a stale state, and they may die. If Connector/J then
re-balances, it might select a dead connection, resulting in
an exception being passed to the application. To help prevent
this, you can use loadBalanceValidateConnectionOnSwapServer
to validate the connection before use.
If your Connector/J deployment uses a connection pool that
allows you to specify a validation query, take advantage of
it, but ensure that the query starts exactly with /* ping */.
This is particularly important if you are using the
load-balancing or replication-aware features of Connector/J,
as it will help keep alive connections which otherwise will
go stale and die, causing problems later.
Chapter 8 Multi-Host Connections
The following sections discuss a number of topics that
involve multi-host connections, namely, server
load-balancing, failover, and replication.
Developers should know the following things about multi-host
connections that are managed through Connector/J:
* Each multi-host connection is a wrapper of the underlying
physical connections.
* Each of the underlying physical connections has its own
session. Sessions cannot be tracked, shared, or copied,
given the MySQL architecture.
* Every switch between physical connections means a switch
between sessions.
* Within a transaction boundary, there are no switches
between physical connections. Beyond a transaction
boundary, there is no guarantee that a switch does not
occur.
Note
If an application reuses session-scope data (for example,
variables, SSPs) beyond a transaction boundary, failures
are possible, as a switch between the physical
connections (which is also a switch between sessions)
might occur. Therefore, the application should re-prepare
the session data and also restart the last transaction in
case of an exception, or it should re-prepare session
data for each new transaction if it does not want to deal
with exception handling.
8.1 Configuring Server Failover
MySQL Connector/J supports server failover. A failover
happens when connection-related errors occur for an
underlying, active connection. The connection errors are, by
default, propagated to the client, which has to handle them
by, for example, recreating the working objects (Statement,
ResultSet, etc.) and restarting the processes. Sometimes, the
driver might eventually fall back to the original host
automatically before the client application continues to run,
in which case the host switch is transparent and the client
application will not even notice it.
A connection using failover support works just like a
standard connection: the client does not experience any
disruptions in the failover process. This means the client
can rely on the same connection instance even if two
successive statements might be executed on two different
physical hosts. However, this does not mean the client does
not have to deal with the exception that triggered the server
switch.
The failover is configured at the initial setup stage of the
server connection by the connection URL (see explanations for
its format here):
jdbc:mysql://[primary host][:port],[secondary host 1][:port][,[seconda
ry host 2][:port]]...[/[database]]??
[?propertyName1=propertyValue1[&propertyName2=propertyValue2]...]
The host list in the connection URL comprises of two types of
hosts, the primary and the secondary. When starting a new
connection, the driver always tries to connect to the primary
host first and, if required, fails over to the secondary
hosts on the list sequentially when communication problems
are experienced. Even if the initial connection to the
primary host fails and the driver gets connected to a
secondary host, the primary host never loses its special
status: for example, it can be configured with an access mode
distinct from those of the secondary hosts, and it can be put
on a higher priority when a host is to be picked during a
failover process.
The failover support is configured by the following
connection properties (their functions are explained in the
paragraphs below):
* failOverReadOnly
* secondsBeforeRetryMaster
* queriesBeforeRetryMaster
* retriesAllDown
* autoReconnect
* autoReconnectForPools
Configuring Connection Access Mode
As with any standard connection, the initial connection to
the primary host is in read/write mode. However, if the
driver fails to establish the initial connection to the
primary host and it automatically switches to the next host
on the list, the access mode now depends on the value of the
property failOverReadOnly, which is "true" by default. The
same happens if the driver is initially connected to the
primary host and, because of some connection failure, it
fails over to a secondary host. Every time the connection
falls back to the primary host, its access mode will be
read/write, irrespective of whether or not the primary host
has been connected to before. The connection access mode can
be changed any time at runtime by calling the method
Connection.setReadOnly(boolean), which partially overrides
the property failOverReadOnly. When failOverReadOnly=false
and the access mode is explicitly set to either true or
false, it becomes the mode for every connection after a host
switch, no matter what host type are we connected to; but, if
failOverReadOnly=true, changing the access mode to read/write
is only possible if the driver is connecting to the primary
host; however, even if the access mode cannot be changed for
the current connection, the driver remembers the client's
last intention and, when falling back to the primary host,
that is the mode that will be used. For an illustration, see
the following successions of events with a two-host
connection.
* Sequence A, with failOverReadOnly=true:
1. Connects to primary host in read/write mode
2. Sets Connection.setReadOnly(true); primary host now
in read-only mode
3. Failover event; connects to secondary host in
read-only mode
4. Sets Connection.setReadOnly(false); secondary host
remains in read-only mode
5. Falls back to primary host; connection now in
read/write mode
* Sequence B, with failOverReadOnly=false
1. Connects to primary host in read/write mode
2. Sets Connection.setReadOnly(true); primary host now
in read-only mode
3. Failover event; connects to secondary host in
read-only mode
4. Set Connection.setReadOnly(false); connection to
secondary host switches to read/write mode
5. Falls back to primary host; connection now in
read/write mode
The difference between the two scenarios is in step 4: the
access mode for the secondary host in sequence A does not
change at that step, but the driver remembers and uses the
set mode when falling back to the primary host, which would
be read-only otherwise; but in sequence B, the access mode
for the secondary host changes immediately.
Configuring Fallback to Primary Host
As already mentioned, the primary host is special in the
failover arrangement when it comes to the host's access mode.
Additionally, the driver tries to fall back to the primary
host as soon as possible by default, even if no communication
exception occurs. Two properties, secondsBeforeRetryMaster
and queriesBeforeRetryMaster, determine when the driver is
ready to retry a reconnection to the primary host (the Master
in the property names stands for the primary host of our
connection URL, which is not necessarily a master host in a
replication setup; the naming was maintained for back
compatibility with Connector/J versions prior to 5.1.35):
* secondsBeforeRetryMaster determines how much time the
driver waits before trying to fall back to the primary
host
* queriesBeforeRetryMaster determines the number of queries
that are executed before the driver tries to fall back to
the primary host. Note that for the driver, each call to
a Statement.execute*() method increments the query
execution counter; therefore, when calls are made to
Statement.executeBatch() or if allowMultiQueries or
rewriteBatchStatements are enabled, the driver may not
have an accurate count of the actual number of queries
executed on the server. Also, the driver calls the
Statement.execute*() methods internally in several
occasions. All these mean you can only use
queriesBeforeRetryMaster only as a coarse specification
for when to fall back to the primary host.
In general, an attempt to fallback to the primary host is
made when at least one of the conditions specified by the two
properties is met, and the attempt always takes place at
transaction boundaries. However, if auto-commit is turned
off, the check happens only when the method
Connection.commit() or Connection.rollback() is called. The
automatic fallback to the primary host can be turned off by
setting simultaneously secondsBeforeRetryMaster and
queriesBeforeRetryMaster to "0". Setting only one of the
properties to "0" only disables one part of the check.
Configuring Reconnection Attempts
When establishing a new connection or when a failover event
occurs, the driver tries to connect successively to the next
candidate on the host list. When the end of the list has been
reached, it restarts all over again from the beginning of the
list; however, the primary host is skipped over, if (a) NOT
all the secondary hosts have already been tested at least
once, AND (b) the fallback conditions defined by
secondsBeforeRetryMaster and queriesBeforeRetryMaster are not
yet fulfilled. Each run-through of the whole host list,
(which is not necessarily completed at the end of the host
list) counts as a single connection attempt. The driver tries
as many connection attempts as specified by the value of the
property retriesAllDown.
Seamless Reconnection
Although not recommended, you can make the driver perform
failovers without invalidating the active Statement or
ResultSet instances by setting either the parameter
autoReconnect or autoReconnectForPools to true. This allows
the client to continue using the same object instances after
a failover event, without taking any exceptional measures.
This, however, may lead to unexpected results: for example,
if the driver is connected to the primary host with
read/write access mode and it fails-over to a secondary host
in real-only mode, further attempts to issue data-changing
queries will result in errors, and the client will not be
aware of that. This limitation is particularly relevant when
using data streaming: after the failover, the ResultSet looks
to be alright, but the underlying connection may have changed
already, and no backing cursor is available anymore.
8.2 Configuring Load Balancing with Connector/J
Connector/J has long provided an effective means to
distribute read/write load across multiple MySQL server
instances for Cluster or master-master replication
deployments. Starting with Connector/J 5.1.3, you can now
dynamically configure load-balanced connections, with no
service outage. In-process transactions are not lost, and no
application exceptions are generated if any application is
trying to use that particular server instance.
The load balancing is configured at the initial setup stage
of the server connection by the following connection URL,
which has a similar format as the general URL for MySQL
connection, but a specialized scheme:
jdbc:mysql:loadbalance://[host1][:port],[host2][:port][,[host3][:port]
]...[/[database]] ??
[?propertyName1=propertyValue1[&propertyName2=propertyValue2]...]
There are two configuration properties associated with this
functionality:
* loadBalanceConnectionGroup - This provides the ability to
group connections from different sources. This allows you
to manage these JDBC sources within a single class loader
in any combination you choose. If they use the same
configuration, and you want to manage them as a logical
single group, give them the same name. This is the key
property for management: if you do not define a name
(string) for loadBalanceConnectionGroup, you cannot
manage the connections. All load-balanced connections
sharing the same loadBalanceConnectionGroup value,
regardless of how the application creates them, will be
managed together.
* loadBalanceEnableJMX - The ability to manage the
connections is exposed when you define a
loadBalanceConnectionGroup; but if you want to manage
this externally, enable JMX by setting this property to
true. This enables a JMX implementation, which exposes
the management and monitoring operations of a connection
group. Further, start your application with the
-Dcom.sun.management.jmxremote JVM flag. You can then
perform connect and perform operations using a JMX client
such as jconsole.
Once a connection has been made using the correct connection
properties, a number of monitoring properties are available:
* Current active host count.
* Current active physical connection count.
* Current active logical connection count.
* Total logical connections created.
* Total transaction count.
The following management operations can also be performed:
* Add host.
* Remove host.
The JMX interface,
com.mysql.jdbc.jmx.LoadBalanceConnectionGroupManagerMBean,
has the following methods:
* int getActiveHostCount(String group);
* int getTotalHostCount(String group);
* long getTotalLogicalConnectionCount(String group);
* long getActiveLogicalConnectionCount(String group);
* long getActivePhysicalConnectionCount(String group);
* long getTotalPhysicalConnectionCount(String group);
* long getTotalTransactionCount(String group);
* void removeHost(String group, String host) throws
SQLException;
* void stopNewConnectionsToHost(String group, String host)
throws SQLException;
* void addHost(String group, String host, boolean
forExisting);
* String getActiveHostsList(String group);
* String getRegisteredConnectionGroups();
The getRegisteredConnectionGroups() method returns the names
of all connection groups defined in that class loader.
You can test this setup with the following code:
public class Test {
private static String URL = "jdbc:mysql:loadbalance://" +
"localhost:3306,localhost:3310/test?" +
"loadBalanceConnectionGroup=first&loadBalanceEnableJMX=true";
public static void main(String[] args) throws Exception {
new Thread(new Repeater()).start();
new Thread(new Repeater()).start();
new Thread(new Repeater()).start();
}
static Connection getNewConnection() throws SQLException, ClassNot
FoundException {
Class.forName("com.mysql.jdbc.Driver");
return DriverManager.getConnection(URL, "root", "");
}
static void executeSimpleTransaction(Connection c, int conn, int t
rans){
try {
c.setAutoCommit(false);
Statement s = c.createStatement();
s.executeQuery("SELECT SLEEP(1) /* Connection: " + conn +
", transaction: " + trans + " */");
c.commit();
} catch (SQLException e) {
e.printStackTrace();
}
}
public static class Repeater implements Runnable {
public void run() {
for(int i=0; i < 100; i++){
try {
Connection c = getNewConnection();
for(int j=0; j < 10; j++){
executeSimpleTransaction(c, i, j);
Thread.sleep(Math.round(100 * Math.random()));
}
c.close();
Thread.sleep(100);
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
}
After compiling, the application can be started with the
-Dcom.sun.management.jmxremote flag, to enable remote
management. jconsole can then be started. The Test main class
will be listed by jconsole. Select this and click Connect.
You can then navigate to the
com.mysql.jdbc.jmx.LoadBalanceConnectionGroupManager bean. At
this point, you can click on various operations and examine
the returned result.
If you now had an additional instance of MySQL running on
port 3309, you could ensure that Connector/J starts using it
by using the addHost(), which is exposed in jconsole. Note
that these operations can be performed dynamically without
having to stop the application running.
For further information on the combination of load balancing
and failover, see Section 8.4, "Advanced Load-balancing and
Failover Configuration."
8.3 Configuring Master/Slave Replication with Connector/J
This section describe a number of features of Connector/J's
support for replication-aware deployments.
The replication is configured at the initial setup stage of
the server connection by the connection URL, which has a
similar format as the general URL for MySQL connection, but a
specialized scheme:
jdbc:mysql:replication://[master host][:port],[slave host 1][:port][,[
slave host 2][:port]]...[/[database]] ??
[?propertyName1=propertyValue1[&propertyName2=propertyValue2]...]
Users may specify the property
allowMasterDownConnections=true to allow Connection objects
to be created even though no master hosts are reachable. Such
Connection objects report they are read-only, and
isMasterConnection() returns false for them. The Connection
tests for available master hosts when
Connection.setReadOnly(false) is called, throwing an
SQLException if it cannot establish a connection to a master,
or switching to a master connection if the host is available.
For Connector/J 5.1.38 and later, users may specify the
property allowSlavesDownConnections=true to allow Connection
objects to be created even though no slave hosts are
reachable. A Connection then, at runtime, tests for available
slave hosts when Connection.setReadOnly(true) is called (see
explanation for the method below), throwing an SQLException
if it cannot establish a connection to a slave, unless the
property readFromMasterWhenNoSlaves is set to be "true" (see
below for a description of the property).
Scaling out Read Load by Distributing Read Traffic to Slaves
Connector/J 3.1.7 and higher includes a variant of the driver
that will automatically send queries to a read/write master,
or a failover or round-robin loadbalanced set of slaves based
on the state of Connection.getReadOnly().
An application signals that it wants a transaction to be
read-only by calling Connection.setReadOnly(true). The
replication-aware connection will use one of the slave
connections, which are load-balanced per slave host using a
round-robin scheme. A given connection is sticky to a slave
until a transaction boundary command (a commit or rollback)
is issued, or until the slave is removed from service. For
Connector/J 5.1.38 and later, after calling
Connection.setReadOnly(true), if you want to allow connection
to a master when no slaves are available, set the property
readFromMasterWhenNoSlaves to "true." Notice that the master
host will be used in read-only state in those cases, as if it
is a slave host. Also notice that setting
readFromMasterWhenNoSlaves=true might result in an extra load
for the master host in a transparent manner.
If you have a write transaction, or if you have a read that
is time-sensitive (remember, replication in MySQL is
asynchronous), set the connection to be not read-only, by
calling Connection.setReadOnly(false) and the driver will
ensure that further calls are sent to the master MySQL
server. The driver takes care of propagating the current
state of autocommit, isolation level, and catalog between all
of the connections that it uses to accomplish this load
balancing functionality.
To enable this functionality, use the
com.mysql.jdbc.ReplicationDriver class when configuring your
application server's connection pool or when creating an
instance of a JDBC driver for your standalone application.
Because it accepts the same URL format as the standard MySQL
JDBC driver, ReplicationDriver does not currently work with
java.sql.DriverManager-based connection creation unless it is
the only MySQL JDBC driver registered with the DriverManager
.
Here is a short example of how ReplicationDriver might be
used in a standalone application:
import java.sql.Connection;
import java.sql.ResultSet;
import java.util.Properties;
import com.mysql.jdbc.ReplicationDriver;
public class ReplicationDriverDemo {
public static void main(String[] args) throws Exception {
ReplicationDriver driver = new ReplicationDriver();
Properties props = new Properties();
// We want this for failover on the slaves
props.put("autoReconnect", "true");
// We want to load balance between the slaves
props.put("roundRobinLoadBalance", "true");
props.put("user", "foo");
props.put("password", "bar");
//
// Looks like a normal MySQL JDBC url, with a
// comma-separated list of hosts, the first
// being the 'master', the rest being any number
// of slaves that the driver will load balance against
//
Connection conn =
driver.connect("jdbc:mysql:replication://master,slave1,slave2,
slave3/test",
props);
//
// Perform read/write work on the master
// by setting the read-only flag to "false"
//
conn.setReadOnly(false);
conn.setAutoCommit(false);
conn.createStatement().executeUpdate("UPDATE some_table ....");
conn.commit();
//
// Now, do a query from a slave, the driver automatically picks on
e
// from the list
//
conn.setReadOnly(true);
ResultSet rs =
conn.createStatement().executeQuery("SELECT a,b FROM alt_table")
;
.......
}
}
Consider using the Load Balancing JDBC Pool (lbpool) tool,
which provides a wrapper around the standard JDBC driver and
enables you to use DB connection pools that includes checks
for system failures and uneven load distribution. For more
information, see Load Balancing JDBC Driver for MySQL
(mysql-lbpool) (http://code.google.com/p/mysql-lbpool/).
Support for Multiple-Master Replication Topographies
Since Connector/J 5.1.27, multi-master replication
topographies are supported.
The connection URL for replication discussed earlier (i.e.,
in the format of
jdbc:mysql:replication://master,slave1,slave2,slave3/test)
assumes that the first (and only the first) host is the
master. Supporting deployments with an arbitrary number of
masters and slaves requires a different URL syntax for
specifying the hosts and the properties for specific hosts,
which is just an expansion of the URL syntax discussed in
Section 5.1, "" with the property type=[master|slave]; for
example:
jdbc:mysql://address=(type=master)(host=master1host),address=(type=mas
ter)(host=master2host),address=(type=slave)(host=slave1host)/database
Connector/J uses a load-balanced connection internally for
management of the master connections, which means that
ReplicationConnection, when configured to use multiple
masters, exposes the same options to balance load across
master hosts as described in Section 8.2, "Configuring Load
Balancing with Connector/J."
Live Reconfiguration of Replication Topography
Since Connector/J 5.1.28, live management of replication host
(single or multi-master) topographies is also supported. This
enables users to promote slaves for Java applications without
requiring an application restart.
The replication hosts are most effectively managed in the
context of a replication connection group. A
ReplicationConnectionGroup class represents a logical
grouping of connections which can be managed together. There
may be one or more such replication connection groups in a
given Java class loader (there can be an application with two
different JDBC resources needing to be managed
independently). This key class exposes host management
methods for replication connections, and
ReplicationConnection objects register themselves with the
appropriate ReplicationConnectionGroup if a value for the new
replicationConnectionGroup property is specified. The
ReplicationConnectionGroup object tracks these connections
until they are closed, and it is used to manipulate the hosts
associated with these connections.
Some important methods related to host management include:
* getMasterHosts(): Returns a collection of strings
representing the hosts configured as masters
* getSlaveHosts(): Returns a collection of strings
representing the hosts configured as slaves
* addSlaveHost(String host): Adds new host to pool of
possible slave hosts for selection at start of new
read-only workload
* promoteSlaveToMaster(String host): Removes the host from
the pool of potential slaves for future read-only
processes (existing read-only process is allowed to
continue to completion) and adds the host to the pool of
potential master hosts
* removeSlaveHost(String host, boolean closeGently):
Removes the host (host name match must be exact) from the
list of configured slaves; if closeGently is false,
existing connections which have this host as currently
active will be closed hardly (application should expect
exceptions)
* removeMasterHost(String host, boolean closeGently): Same
as removeSlaveHost(), but removes the host from the list
of configured masters
Some useful management metrics include:
* getConnectionCountWithHostAsSlave(String host): Returns
the number of ReplicationConnection objects that have the
given host configured as a possible slave
* getConnectionCountWithHostAsMaster(String host): Returns
the number of ReplicationConnection objects that have the
given host configured as a possible master
* getNumberOfSlavesAdded(): Returns the number of times a
slave host has been dynamically added to the group pool
* getNumberOfSlavesRemoved(): Returns the number of times a
slave host has been dynamically removed from the group
pool
* getNumberOfSlavePromotions(): Returns the number of times
a slave host has been promoted to a master
* getTotalConnectionCount(): Returns the number of
ReplicationConnection objects which have been registered
with this group
* getActiveConnectionCount(): Returns the number of
ReplicationConnection objects currently being managed by
this group
ReplicationConnectionGroupManager
com.mysql.jdbc.ReplicationConnectionGroupManager provides
access to the replication connection groups, together with
some utility methods.
* getConnectionGroup(String groupName): Returns the
ReplicationConnectionGroup object matching the groupName
provided
The other methods in ReplicationConnectionGroupManager mirror
those of ReplicationConnectionGroup, except that the first
argument is a String group name. These methods will operate
on all matching ReplicationConnectionGroups, which are
helpful for removing a server from service and have it
decommissioned across all possible
ReplicationConnectionGroups.
These methods might be useful for in-JVM management of
replication hosts if an application triggers topography
changes. For managing host configurations from outside the
JVM, JMX can be used.
Using JMX for Managing Replication Hosts
When Connector/J is started with replicationEnableJMX=true
and a value set for the property replicationConnectionGroup,
a JMX MBean will be registered, allowing manipulation of
replication hosts by a JMX client. The MBean interface is
defined in com.mysql.jdbc.jmx.ReplicationGroupManagerMBean,
and leverages the ReplicationConnectionGroupManager static
methods:
public abstract void addSlaveHost(String groupFilter, String host) th
rows SQLException;
public abstract void removeSlaveHost(String groupFilter, String host)
throws SQLException;
public abstract void promoteSlaveToMaster(String groupFilter, String
host) throws SQLException;
public abstract void removeMasterHost(String groupFilter, String host
) throws SQLException;
public abstract String getMasterHostsList(String group);
public abstract String getSlaveHostsList(String group);
public abstract String getRegisteredConnectionGroups();
public abstract int getActiveMasterHostCount(String group);
public abstract int getActiveSlaveHostCount(String group);
public abstract int getSlavePromotionCount(String group);
public abstract long getTotalLogicalConnectionCount(String group);
public abstract long getActiveLogicalConnectionCount(String group);
8.4 Advanced Load-balancing and Failover Configuration
Connector/J provides a useful load-balancing implementation
for MySQL Cluster or multi-master deployments, as explained
in Section 8.2, "Configuring Load Balancing with Connector/J"
and Section 8.3, "." As of Connector/J 5.1.12, this same
implementation is used for balancing load between read-only
slaves with ReplicationDriver.
When trying to balance workload between multiple servers, the
driver has to determine when it is safe to swap servers,
doing so in the middle of a transaction, for example, could
cause problems. It is important not to lose state
information. For this reason, Connector/J will only try to
pick a new server when one of the following happens:
1. At transaction boundaries (transactions are explicitly
committed or rolled back).
2. A communication exception (SQL State starting with "08")
is encountered.
3. When a SQLException matches conditions defined by user,
using the extension points defined by the
loadBalanceSQLStateFailover,
loadBalanceSQLExceptionSubclassFailover or
loadBalanceExceptionChecker properties.
The third condition revolves around three new properties
introduced with Connector/J 5.1.13. It allows you to control
which SQLExceptions trigger failover.
* loadBalanceExceptionChecker - The
loadBalanceExceptionChecker property is really the key.
This takes a fully-qualified class name which implements
the new com.mysql.jdbc.LoadBalanceExceptionChecker
interface. This interface is very simple, and you only
need to implement the following method:
public boolean shouldExceptionTriggerFailover(SQLException ex)
A SQLException is passed in, and a boolean returned. A
value of true triggers a failover, false does not.
You can use this to implement your own custom logic. An
example where this might be useful is when dealing with
transient errors when using MySQL Cluster, where certain
buffers may become overloaded. The following code snippet
illustrates this:
public class NdbLoadBalanceExceptionChecker
extends StandardLoadBalanceExceptionChecker {
public boolean shouldExceptionTriggerFailover(SQLException ex) {
return super.shouldExceptionTriggerFailover(ex)
|| checkNdbException(ex);
}
private boolean checkNdbException(SQLException ex){
// Have to parse the message since most NDB errors
// are mapped to the same DEMC.
return (ex.getMessage().startsWith("Lock wait timeout exceeded") ||
(ex.getMessage().startsWith("Got temporary error")
&& ex.getMessage().endsWith("from NDB")));
}
}
The code above extends
com.mysql.jdbc.StandardLoadBalanceExceptionChecker, which
is the default implementation. There are a few convenient
shortcuts built into this, for those who want to have
some level of control using properties, without writing
Java code. This default implementation uses the two
remaining properties: loadBalanceSQLStateFailover and
loadBalanceSQLExceptionSubclassFailover.
* loadBalanceSQLStateFailover - allows you to define a
comma-delimited list of SQLState code prefixes, against
which a SQLException is compared. If the prefix matches,
failover is triggered. So, for example, the following
would trigger a failover if a given SQLException starts
with "00", or is "12345":
loadBalanceSQLStateFailover=00,12345
* loadBalanceSQLExceptionSubclassFailover - can be used in
conjunction with loadBalanceSQLStateFailover or on its
own. If you want certain subclasses of SQLException to
trigger failover, simply provide a comma-delimited list
of fully-qualified class or interface names to check
against. For example, if you want all
SQLTransientConnectionExceptions to trigger failover, you
would specify:
loadBalanceSQLExceptionSubclassFailover=java.sql.SQLTransientConnectio
nException
While the three failover conditions enumerated earlier suit
most situations, if autocommit is enabled, Connector/J never
re-balances, and continues using the same physical
connection. This can be problematic, particularly when
load-balancing is being used to distribute read-only load
across multiple slaves. However, Connector/J can be
configured to re-balance after a certain number of statements
are executed, when autocommit is enabled. This functionality
is dependent upon the following properties:
* loadBalanceAutoCommitStatementThreshold - defines the
number of matching statements which will trigger the
driver to potentially swap physical server connections.
The default value, 0, retains the behavior that
connections with autocommit enabled are never balanced.
* loadBalanceAutoCommitStatementRegex - the regular
expression against which statements must match. The
default value, blank, matches all statements. So, for
example, using the following properties will cause
Connector/J to re-balance after every third statement
that contains the string "test":
loadBalanceAutoCommitStatementThreshold=3
loadBalanceAutoCommitStatementRegex=.*test.*
loadBalanceAutoCommitStatementRegex can prove useful in a
number of situations. Your application may use temporary
tables, server-side session state variables, or
connection state, where letting the driver arbitrarily
swap physical connections before processing is complete
could cause data loss or other problems. This allows you
to identify a trigger statement that is only executed
when it is safe to swap physical connections.
Chapter 9 Using the Connector/J Interceptor Classes
An interceptor is a software design pattern that provides a
transparent way to extend or modify some aspect of a program,
similar to a user exit. No recompiling is required. With
Connector/J, the interceptors are enabled and disabled by
updating the connection string to refer to different sets of
interceptor classes that you instantiate.
The connection properties that control the interceptors are
explained in Section 5.1, "Driver/Datasource Class Names, URL
Syntax and Configuration Properties for Connector/J:"
* connectionLifecycleInterceptors, where you specify the
fully qualified names of classes that implement the
com.mysql.jdbc.ConnectionLifecycleInterceptor interface.
In these kinds of interceptor classes, you might log
events such as rollbacks, measure the time between
transaction start and end, or count events such as calls
to setAutoCommit().
* exceptionInterceptors, where you specify the fully
qualified names of classes that implement the
com.mysql.jdbc.ExceptionInterceptor interface. In these
kinds of interceptor classes, you might add extra
diagnostic information to exceptions that can have
multiple causes or indicate a problem with server
settings. Because exceptionInterceptors classes are only
called when handling a SQLException thrown from
Connector/J code, they can be used even in production
deployments without substantial performance overhead.
* statementInterceptors, where you specify the fully
qualified names of classes that implement the
com.mysql.jdbc.StatementInterceptorV2 interface. In these
kinds of interceptor classes, you might change or augment
the processing done by certain kinds of statements, such
as automatically checking for queried data in a memcached
server, rewriting slow queries, logging information about
statement execution, or route requests to remote servers.
Chapter 10 Using Connector/J with Tomcat
The following instructions are based on the instructions for
Tomcat-5.x, available at
http://tomcat.apache.org/tomcat-5.5-doc/jndi-datasource-examp
les-howto.html which is current at the time this document was
written.
First, install the .jar file that comes with Connector/J in
$CATALINA_HOME/common/lib so that it is available to all
applications installed in the container.
Next, configure the JNDI DataSource by adding a declaration
resource to $CATALINA_HOME/conf/server.xml in the context
that defines your web application:
<Context ....>
...
<Resource name="jdbc/MySQLDB"
auth="Container"
type="javax.sql.DataSource"/>
<ResourceParams name="jdbc/MySQLDB">
<parameter>
<name>factory</name>
<value>org.apache.commons.dbcp.BasicDataSourceFactory</value>
</parameter>
<parameter>
<name>maxActive</name>
<value>10</value>
</parameter>
<parameter>
<name>maxIdle</name>
<value>5</value>
</parameter>
<parameter>
<name>validationQuery</name>
<value>SELECT 1</value>
</parameter>
<parameter>
<name>testOnBorrow</name>
<value>true</value>
</parameter>
<parameter>
<name>testWhileIdle</name>
<value>true</value>
</parameter>
<parameter>
<name>timeBetweenEvictionRunsMillis</name>
<value>10000</value>
</parameter>
<parameter>
<name>minEvictableIdleTimeMillis</name>
<value>60000</value>
</parameter>
<parameter>
<name>username</name>
<value>someuser</value>
</parameter>
<parameter>
<name>password</name>
<value>somepass</value>
</parameter>
<parameter>
<name>driverClassName</name>
<value>com.mysql.jdbc.Driver</value>
</parameter>
<parameter>
<name>url</name>
<value>jdbc:mysql://localhost:3306/test</value>
</parameter>
</ResourceParams>
</Context>
Note that Connector/J 5.1.3 introduced a facility whereby,
rather than use a validationQuery value of SELECT 1, it is
possible to use validationQuery with a value set to /* ping
*/. This sends a ping to the server which then returns a fake
result set. This is a lighter weight solution. It also has
the advantage that if using ReplicationConnection or
LoadBalancedConnection type connections, the ping will be
sent across all active connections. The following XML snippet
illustrates how to select this option:
<parameter>
<name>validationQuery</name>
<value>/* ping */</value>
</parameter>
Note that /* ping */ has to be specified exactly.
In general, follow the installation instructions that come
with your version of Tomcat, as the way you configure
datasources in Tomcat changes from time to time, and if you
use the wrong syntax in your XML file, you will most likely
end up with an exception similar to the following:
Error: java.sql.SQLException: Cannot load JDBC driver class 'null ' SQ
L
state: null
Note that the auto-loading of drivers having the
META-INF/service/java.sql.Driver class in JDBC 4.0 and above
causes an improper undeployment of the Connector/J driver in
Tomcat on Windows. Namely, the Connector/J jar remains
locked. This is an initialization problem that is not related
to the driver. The possible workarounds, if viable, are as
follows: use "antiResourceLocking=true" as a Tomcat Context
attribute, or remove the META-INF/ directory.
Chapter 11 Using Connector/J with JBoss
These instructions cover JBoss-4.x. To make the JDBC driver
classes available to the application server, copy the .jar
file that comes with Connector/J to the lib directory for
your server configuration (which is usually called default).
Then, in the same configuration directory, in the
subdirectory named deploy, create a datasource configuration
file that ends with -ds.xml, which tells JBoss to deploy this
file as a JDBC Datasource. The file should have the following
contents:
<datasources>
<local-tx-datasource>
<jndi-name>MySQLDB</jndi-name>
<connection-url>jdbc:mysql://localhost:3306/dbname</connection
-url>
<driver-class>com.mysql.jdbc.Driver</driver-class>
<user-name>user</user-name>
<password>pass</password>
<min-pool-size>5</min-pool-size>
<max-pool-size>20</max-pool-size>
<idle-timeout-minutes>5</idle-timeout-minutes>
<exception-sorter-class-name>
com.mysql.jdbc.integration.jboss.ExtendedMysqlExceptionSorter
</exception-sorter-class-name>
<valid-connection-checker-class-name>
com.mysql.jdbc.integration.jboss.MysqlValidConnectionChecker
</valid-connection-checker-class-name>
</local-tx-datasource>
</datasources>
Chapter 12 Using Connector/J with Spring
The Spring Framework is a Java-based application framework
designed for assisting in application design by providing a
way to configure components. The technique used by Spring is
a well known design pattern called Dependency Injection (see
Inversion of Control Containers and the Dependency Injection
pattern
(http://www.martinfowler.com/articles/injection.html)). This
article will focus on Java-oriented access to MySQL databases
with Spring 2.0. For those wondering, there is a .NET port of
Spring appropriately named Spring.NET.
Spring is not only a system for configuring components, but
also includes support for aspect oriented programming (AOP).
This is one of the main benefits and the foundation for
Spring's resource and transaction management. Spring also
provides utilities for integrating resource management with
JDBC and Hibernate.
For the examples in this section the MySQL world sample
database will be used. The first task is to set up a MySQL
data source through Spring. Components within Spring use the
"bean" terminology. For example, to configure a connection to
a MySQL server supporting the world sample database, you
might use:
<util:map id="dbProps">
<entry key="db.driver" value="com.mysql.jdbc.Driver"/>
<entry key="db.jdbcurl" value="jdbc:mysql://localhost/world"/>
<entry key="db.username" value="myuser"/>
<entry key="db.password" value="mypass"/>
</util:map>
In the above example, we are assigning values to properties
that will be used in the configuration. For the datasource
configuration:
<bean id="dataSource"
class="org.springframework.jdbc.datasource.DriverManagerDataSou
rce">
<property name="driverClassName" value="${db.driver}"/>
<property name="url" value="${db.jdbcurl}"/>
<property name="username" value="${db.username}"/>
<property name="password" value="${db.password}"/>
</bean>
The placeholders are used to provide values for properties of
this bean. This means that you can specify all the properties
of the configuration in one place instead of entering the
values for each property on each bean. We do, however, need
one more bean to pull this all together. The last bean is
responsible for actually replacing the placeholders with the
property values.
<bean
class="org.springframework.beans.factory.config.PropertyPlaceholderCo
nfigurer">
<property name="properties" ref="dbProps"/>
</bean>
Now that we have our MySQL data source configured and ready
to go, we write some Java code to access it. The example
below will retrieve three random cities and their
corresponding country using the data source we configured
with Spring.
// Create a new application context. this processes the Spring config
ApplicationContext ctx =
new ClassPathXmlApplicationContext("ex1appContext.xml");
// Retrieve the data source from the application context
DataSource ds = (DataSource) ctx.getBean("dataSource");
// Open a database connection using Spring's DataSourceUtils
Connection c = DataSourceUtils.getConnection(ds);
try {
// retrieve a list of three random cities
PreparedStatement ps = c.prepareStatement(
"select City.Name as 'City', Country.Name as 'Country' " +
"from City inner join Country on City.CountryCode = Country.Co
de " +
"order by rand() limit 3");
ResultSet rs = ps.executeQuery();
while(rs.next()) {
String city = rs.getString("City");
String country = rs.getString("Country");
System.out.printf("The city %s is in %s%n", city, country);
}
} catch (SQLException ex) {
// something has failed and we print a stack trace to analyse the
error
ex.printStackTrace();
// ignore failure closing connection
try { c.close(); } catch (SQLException e) { }
} finally {
// properly release our connection
DataSourceUtils.releaseConnection(c, ds);
}
This is very similar to normal JDBC access to MySQL with the
main difference being that we are using DataSourceUtils
instead of the DriverManager to create the connection.
While it may seem like a small difference, the implications
are somewhat far reaching. Spring manages this resource in a
way similar to a container managed data source in a J2EE
application server. When a connection is opened, it can be
subsequently accessed in other parts of the code if it is
synchronized with a transaction. This makes it possible to
treat different parts of your application as transactional
instead of passing around a database connection.
12.1 Using JdbcTemplate
Spring makes extensive use of the Template method design
pattern (see Template Method Pattern
(http://en.wikipedia.org/wiki/Template_method_pattern)). Our
immediate focus will be on the JdbcTemplate and related
classes, specifically NamedParameterJdbcTemplate. The
template classes handle obtaining and releasing a connection
for data access when one is needed.
The next example shows how to use NamedParameterJdbcTemplate
inside of a DAO (Data Access Object) class to retrieve a
random city given a country code.
public class Ex2JdbcDao {
/**
* Data source reference which will be provided by Spring.
*/
private DataSource dataSource;
/**
* Our query to find a random city given a country code. Notice
* the ":country" parameter toward the end. This is called a
* named parameter.
*/
private String queryString = "select Name from City " +
"where CountryCode = :country order by rand() limit 1";
/**
* Retrieve a random city using Spring JDBC access classes.
*/
public String getRandomCityByCountryCode(String cntryCode) {
// A template that permits using queries with named parameter
s
NamedParameterJdbcTemplate template =
new NamedParameterJdbcTemplate(dataSource);
// A java.util.Map is used to provide values for the paramete
rs
Map params = new HashMap();
params.put("country", cntryCode);
// We query for an Object and specify what class we are expec
ting
return (String)template.queryForObject(queryString, params, S
tring.class);
}
/**
* A JavaBean setter-style method to allow Spring to inject the dat
a source.
* @param dataSource
*/
public void setDataSource(DataSource dataSource) {
this.dataSource = dataSource;
}
}
The focus in the above code is on the
getRandomCityByCountryCode() method. We pass a country code
and use the NamedParameterJdbcTemplate to query for a city.
The country code is placed in a Map with the key "country",
which is the parameter is named in the SQL query.
To access this code, you need to configure it with Spring by
providing a reference to the data source.
<bean id="dao" class="code.Ex2JdbcDao">
<property name="dataSource" ref="dataSource"/>
</bean>
At this point, we can just grab a reference to the DAO from
Spring and call getRandomCityByCountryCode().
// Create the application context
ApplicationContext ctx =
new ClassPathXmlApplicationContext("ex2appContext.xml");
// Obtain a reference to our DAO
Ex2JdbcDao dao = (Ex2JdbcDao) ctx.getBean("dao");
String countryCode = "USA";
// Find a few random cities in the US
for(int i = 0; i < 4; ++i)
System.out.printf("A random city in %s is %s%n", countryCode,
dao.getRandomCityByCountryCode(countryCode));
This example shows how to use Spring's JDBC classes to
completely abstract away the use of traditional JDBC classes
including Connection and PreparedStatement.
12.2 Transactional JDBC Access
You might be wondering how we can add transactions into our
code if we do not deal directly with the JDBC classes. Spring
provides a transaction management package that not only
replaces JDBC transaction management, but also enables
declarative transaction management (configuration instead of
code).
To use transactional database access, we will need to change
the storage engine of the tables in the world database. The
downloaded script explicitly creates MyISAM tables which do
not support transactional semantics. The InnoDB storage
engine does support transactions and this is what we will be
using. We can change the storage engine with the following
statements.
ALTER TABLE City ENGINE=InnoDB;
ALTER TABLE Country ENGINE=InnoDB;
ALTER TABLE CountryLanguage ENGINE=InnoDB;
A good programming practice emphasized by Spring is
separating interfaces and implementations. What this means is
that we can create a Java interface and only use the
operations on this interface without any internal knowledge
of what the actual implementation is. We will let Spring
manage the implementation and with this it will manage the
transactions for our implementation.
First you create a simple interface:
public interface Ex3Dao {
Integer createCity(String name, String countryCode,
String district, Integer population);
}
This interface contains one method that will create a new
city record in the database and return the id of the new
record. Next you need to create an implementation of this
interface.
public class Ex3DaoImpl implements Ex3Dao {
protected DataSource dataSource;
protected SqlUpdate updateQuery;
protected SqlFunction idQuery;
public Integer createCity(String name, String countryCode,
String district, Integer population) {
updateQuery.update(new Object[] { name, countryCode,
district, population });
return getLastId();
}
protected Integer getLastId() {
return idQuery.run();
}
}
You can see that we only operate on abstract query objects
here and do not deal directly with the JDBC API. Also, this
is the complete implementation. All of our transaction
management will be dealt with in the configuration. To get
the configuration started, we need to create the DAO.
<bean id="dao" class="code.Ex3DaoImpl">
<property name="dataSource" ref="dataSource"/>
<property name="updateQuery">...</property>
<property name="idQuery">...</property>
</bean>
Now you need to set up the transaction configuration. The
first thing you must do is create transaction manager to
manage the data source and a specification of what
transaction properties are required for the dao methods.
<bean id="transactionManager"
class="org.springframework.jdbc.datasource.DataSourceTransactionMana
ger">
<property name="dataSource" ref="dataSource"/>
</bean>
<tx:advice id="txAdvice" transaction-manager="transactionManager">
<tx:attributes>
<tx:method name="*"/>
</tx:attributes>
</tx:advice>
The preceding code creates a transaction manager that handles
transactions for the data source provided to it. The txAdvice
uses this transaction manager and the attributes specify to
create a transaction for all methods. Finally you need to
apply this advice with an AOP pointcut.
<aop:config>
<aop:pointcut id="daoMethods"
expression="execution(* code.Ex3Dao.*(..))"/>
<aop:advisor advice-ref="txAdvice" pointcut-ref="daoMethods"/>
</aop:config>
This basically says that all methods called on the Ex3Dao
interface will be wrapped in a transaction. To make use of
this, you only have to retrieve the dao from the application
context and call a method on the dao instance.
Ex3Dao dao = (Ex3Dao) ctx.getBean("dao");
Integer id = dao.createCity(name, countryCode, district, pop);
We can verify from this that there is no transaction
management happening in our Java code and it is all
configured with Spring. This is a very powerful notion and
regarded as one of the most beneficial features of Spring.
12.3 Connection Pooling with Spring
In many situations, such as web applications, there will be a
large number of small database transactions. When this is the
case, it usually makes sense to create a pool of database
connections available for web requests as needed. Although
MySQL does not spawn an extra process when a connection is
made, there is still a small amount of overhead to create and
set up the connection. Pooling of connections also alleviates
problems such as collecting large amounts of sockets in the
TIME_WAIT state.
Setting up pooling of MySQL connections with Spring is as
simple as changing the data source configuration in the
application context. There are a number of configurations
that we can use. The first example is based on the Jakarta
Commons DBCP library
(http://jakarta.apache.org/commons/dbcp/). The example below
replaces the source configuration that was based on
DriverManagerDataSource with DBCP's BasicDataSource.
<bean id="dataSource" destroy-method="close"
class="org.apache.commons.dbcp.BasicDataSource">
<property name="driverClassName" value="${db.driver}"/>
<property name="url" value="${db.jdbcurl}"/>
<property name="username" value="${db.username}"/>
<property name="password" value="${db.password}"/>
<property name="initialSize" value="3"/>
</bean>
The configuration of the two solutions is very similar. The
difference is that DBCP will pool connections to the database
instead of creating a new connection every time one is
requested. We have also set a parameter here called
initialSize. This tells DBCP that we want three connections
in the pool when it is created.
Another way to configure connection pooling is to configure a
data source in our J2EE application server. Using JBoss as an
example, you can set up the MySQL connection pool by creating
a file called mysql-local-ds.xml and placing it in the
server/default/deploy directory in JBoss. Once we have this
setup, we can use JNDI to look it up. With Spring, this
lookup is very simple. The data source configuration looks
like this.
<jee:jndi-lookup id="dataSource" jndi-name="java:MySQL_DS"/>
Chapter 13 Using Connector/J with GlassFish
This section explains how to use MySQL Connector/J with
GlassFish (tm) Server Open Source Edition 3.0.1. GlassFish
can be downloaded from the GlassFish website
(https://glassfish.dev.java.net/public/downloadsindex.html#to
p).
Once GlassFish is installed, make sure it can access MySQL
Connector/J. To do this, copy the MySQL Connector/J jar file
to the domain-dir/lib directory. For example, copy
mysql-connector-java-5.1.30-bin.jar to
C:\glassfish-install-path\domains\domain-name\lib. Restart
the GlassFish Application Server. For more information, see
"Integrating the JDBC Driver" in GlassFish Server Open Source
Edition Administration Guide, available at GlassFish Server
Documentation
(https://glassfish.java.net/documentation.html).
You are now ready to create JDBC Connection Pools and JDBC
Resources.
Creating a Connection Pool
1. In the GlassFish Administration Console, using the
navigation tree navigate to Resources, JDBC, Connection
Pools.
2. In the JDBC Connection Pools frame click New. You will
enter a two step wizard.
3. In the Name field under General Settings enter the name
for the connection pool, for example enter MySQLConnPool.
4. In the Resource Type field, select javax.sql.DataSource
from the drop-down listbox.
5. In the Database Vendor field, select MySQL from the
drop-down listbox. Click Next to go to the next page of
the wizard.
6. You can accept the default settings for General Settings,
Pool Settings and Transactions for this example. Scroll
down to Additional Properties.
7. In Additional Properties you will need to ensure the
following properties are set:
+ ServerName - The server to connect to. For local
testing this will be localhost.
+ User - The user name with which to connect to MySQL.
+ Password - The corresponding password for the user.
+ DatabaseName - The database to connect to, for
example the sample MySQL database World.
8. Click Finish to exit the wizard. You will be taken to the
JDBC Connection Pools page where all current connection
pools, including the one you just created, will be
displayed.
9. In the JDBC Connection Pools frame click on the
connection pool you just created. Here, you can review
and edit information about the connection pool. Because
Connector/J does not support optimized validation
queries, go to the Advanced tab, and under Connection
Validation, configure the following settings:
+ Connection Validation - select Required.
+ Validation Method - select table from the drop-down
menu.
+ Table Name - enter DUAL.
10. To test your connection pool click the Ping button at the
top of the frame. A message will be displayed confirming
correct operation or otherwise. If an error message is
received recheck the previous steps, and ensure that
MySQL Connector/J has been correctly copied into the
previously specified location.
Now that you have created a connection pool you will also
need to create a JDBC Resource (data source) for use by your
application.
Creating a JDBC Resource
Your Java application will usually reference a data source
object to establish a connection with the database. This
needs to be created first using the following procedure.
* Using the navigation tree in the GlassFish Administration
Console, navigate to Resources, JDBC, JDBC Resources. A
list of resources will be displayed in the JDBC Resources
frame.
* Click New. The New JDBC Resource frame will be displayed.
* In the JNDI Name field, enter the JNDI name that will be
used to access this resource, for example enter
jdbc/MySQLDataSource.
* In the Pool Name field, select a connection pool you want
this resource to use from the drop-down listbox.
* Optionally, you can enter a description into the
Description field.
* Additional properties can be added if required.
* Click OK to create the new JDBC resource. The JDBC
Resources frame will list all available JDBC Resources.
13.1 A Simple JSP Application with GlassFish, Connector/J and MySQL
This section shows how to deploy a simple JSP application on
GlassFish, that connects to a MySQL database.
This example assumes you have already set up a suitable
Connection Pool and JDBC Resource, as explained in the
preceding sections. It is also assumed you have a sample
database installed, such as world.
The main application code, index.jsp is presented here:
<%@ page import="java.sql.*, javax.sql.*, java.io.*, javax.naming.*" %
>
<html>
<head><title>Hello world from JSP</title></head>
<body>
<%
InitialContext ctx;
DataSource ds;
Connection conn;
Statement stmt;
ResultSet rs;
try {
ctx = new InitialContext();
ds = (DataSource) ctx.lookup("java:comp/env/jdbc/MySQLDataSource")
;
//ds = (DataSource) ctx.lookup("jdbc/MySQLDataSource");
conn = ds.getConnection();
stmt = conn.createStatement();
rs = stmt.executeQuery("SELECT * FROM Country");
while(rs.next()) {
%>
<h3>Name: <%= rs.getString("Name") %></h3>
<h3>Population: <%= rs.getString("Population") %></h3>
<%
}
}
catch (SQLException se) {
%>
<%= se.getMessage() %>
<%
}
catch (NamingException ne) {
%>
<%= ne.getMessage() %>
<%
}
%>
</body>
</html>
In addition two XML files are required: web.xml, and
sun-web.xml. There may be other files present, such as
classes and images. These files are organized into the
directory structure as follows:
index.jsp
WEB-INF
|
- web.xml
- sun-web.xml
The code for web.xml is:
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:x
si="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="htt
p://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2
_4.xsd">
<display-name>HelloWebApp</display-name>
<distributable/>
<resource-ref>
<res-ref-name>jdbc/MySQLDataSource</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<res-auth>Container</res-auth>
<res-sharing-scope>Shareable</res-sharing-scope>
</resource-ref>
</web-app>
The code for sun-web.xml is:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE sun-web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Applicati
on Server 8.1 Servlet 2.4//EN" "http://www.sun.com/software/appserver/
dtds/sun-web-app_2_4-1.dtd">
<sun-web-app>
<context-root>HelloWebApp</context-root>
<resource-ref>
<res-ref-name>jdbc/MySQLDataSource</res-ref-name>
<jndi-name>jdbc/MySQLDataSource</jndi-name>
</resource-ref>
</sun-web-app>
These XML files illustrate a very important aspect of running
JDBC applications on GlassFish. On GlassFish it is important
to map the string specified for a JDBC resource to its JNDI
name, as set up in the GlassFish administration console. In
this example, the JNDI name for the JDBC resource, as
specified in the GlassFish Administration console when
creating the JDBC Resource, was jdbc/MySQLDataSource. This
must be mapped to the name given in the application. In this
example the name specified in the application,
jdbc/MySQLDataSource, and the JNDI name, happen to be the
same, but this does not necessarily have to be the case. Note
that the XML element <res-ref-name> is used to specify the
name as used in the application source code, and this is
mapped to the JNDI name specified using the <jndi-name>
element, in the file sun-web.xml. The resource also has to be
created in the web.xml file, although the mapping of the
resource to a JNDI name takes place in the sun-web.xml file.
If you do not have this mapping set up correctly in the XML
files you will not be able to lookup the data source using a
JNDI lookup string such as:
ds = (DataSource) ctx.lookup("java:comp/env/jdbc/MySQLDataSource");
You will still be able to access the data source directly
using:
ds = (DataSource) ctx.lookup("jdbc/MySQLDataSource");
With the source files in place, in the correct directory
structure, you are ready to deploy the application:
1. In the navigation tree, navigate to Applications - the
Applications frame will be displayed. Click Deploy.
2. You can now deploy an application packaged into a single
WAR file from a remote client, or you can choose a
packaged file or directory that is locally accessible to
the server. If you are simply testing an application
locally you can simply point GlassFish at the directory
that contains your application, without needing to
package the application into a WAR file.
3. Now select the application type from the Type drop-down
listbox, which in this example is Web application.
4. Click OK.
Now, when you navigate to the Applications frame, you will
have the option to Launch, Redeploy, or Restart your
application. You can test your application by clicking
Launch. The application will connection to the MySQL database
and display the Name and Population of countries in the
Country table.
13.2 A Simple Servlet with GlassFish, Connector/J and MySQL
This section describes a simple servlet that can be used in
the GlassFish environment to access a MySQL database. As with
the previous section, this example assumes the sample
database world is installed.
The project is set up with the following directory structure:
index.html
WEB-INF
|
- web.xml
- sun-web.xml
- classes
|
- HelloWebServlet.java
- HelloWebServlet.class
The code for the servlet, located in HelloWebServlet.java, is
as follows:
import javax.servlet.http.*;
import javax.servlet.*;
import java.io.*;
import java.sql.*;
import javax.sql.*;
import javax.naming.*;
public class HelloWebServlet extends HttpServlet {
InitialContext ctx = null;
DataSource ds = null;
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
String sql = "SELECT Name, Population FROM Country WHERE Name=?";
public void init () throws ServletException {
try {
ctx = new InitialContext();
ds = (DataSource) ctx.lookup("java:comp/env/jdbc/MySQLDataSource
");
conn = ds.getConnection();
ps = conn.prepareStatement(sql);
}
catch (SQLException se) {
System.out.println("SQLException: "+se.getMessage());
}
catch (NamingException ne) {
System.out.println("NamingException: "+ne.getMessage());
}
}
public void destroy () {
try {
if (rs != null)
rs.close();
if (ps != null)
ps.close();
if (conn != null)
conn.close();
if (ctx != null)
ctx.close();
}
catch (SQLException se) {
System.out.println("SQLException: "+se.getMessage());
}
catch (NamingException ne) {
System.out.println("NamingException: "+ne.getMessage());
}
}
public void doPost(HttpServletRequest req, HttpServletResponse resp)
{
try {
String country_name = req.getParameter("country_name");
resp.setContentType("text/html");
PrintWriter writer = resp.getWriter();
writer.println("<html><body>");
writer.println("<p>Country: "+country_name+"</p>");
ps.setString(1, country_name);
rs = ps.executeQuery();
if (!rs.next()){
writer.println("<p>Country does not exist!</p>");
}
else {
rs.beforeFirst();
while(rs.next()) {
writer.println("<p>Name: "+rs.getString("Name")+"</p>");
writer.println("<p>Population: "+rs.getString("Population")+
"</p>");
}
}
writer.println("</body></html>");
writer.close();
}
catch (Exception e) {
e.printStackTrace();
}
}
public void doGet(HttpServletRequest req, HttpServletResponse resp){
try {
resp.setContentType("text/html");
PrintWriter writer = resp.getWriter();
writer.println("<html><body>");
writer.println("<p>Hello from servlet doGet()</p>");
writer.println("</body></html>");
writer.close();
}
catch (Exception e) {
e.printStackTrace();
}
}
}
In the preceding code a basic doGet() method is implemented,
but is not used in the example. The code to establish the
connection with the database is as shown in the previous
example, Section 13.1, "A Simple JSP Application with
GlassFish, Connector/J and MySQL," and is most conveniently
located in the servlet init() method. The corresponding
freeing of resources is located in the destroy method. The
main functionality of the servlet is located in the doPost()
method. If the user enters into the input form a country name
that can be located in the database, the population of the
country is returned. The code is invoked using a POST action
associated with the input form. The form is defined in the
file index.html:
<html>
<head><title>HelloWebServlet</title></head>
<body>
<h1>HelloWebServlet</h1>
<p>Please enter country name:</p>
<form action="HelloWebServlet" method="POST">
<input type="text" name="country_name" length="50" />
<input type="submit" value="Submit" />
</form>
</body>
</html>
The XML files web.xml and sun-web.xml are as for the example
in the preceding section, Section 13.1, "A Simple JSP
Application with GlassFish, Connector/J and MySQL," no
additional changes are required.
When compiling the Java source code, you will need to specify
the path to the file javaee.jar. On Windows, this can be done
as follows:
shell> javac -classpath c:\glassfishv3\glassfish\lib\javaee.jar HelloW
ebServlet.java
Once the code is correctly located within its directory
structure, and compiled, the application can be deployed in
GlassFish. This is done in exactly the same way as described
in the preceding section, Section 13.1, "A Simple JSP
Application with GlassFish, Connector/J and MySQL."
Once deployed the application can be launched from within the
GlassFish Administration Console. Enter a country name such
as "England", and the application will return "Country does
not exist!". Enter "France", and the application will return
a population of 59225700.
Chapter 14 Using Connector/J with MySQL Fabric
MySQL Fabric is a system for managing a farm of MySQL servers
(and other components). Fabric provides an extensible and
easy to use system for managing a MySQL deployment for
sharding and high-availability.
For more information on MySQL Fabric, see MySQL Fabric
(http://dev.mysql.com/doc/mysql-utilities/1.5/en/fabric.html)
. For instructions on how to use Connector/J with MySQL
Fabric, see Using Connector/J with MySQL Fabric
(http://dev.mysql.com/doc/mysql-utilities/1.5/en/connector-j-
fabric.html).
Chapter 15 Troubleshooting Connector/J Applications
This section explains the symptoms and resolutions for the
most commonly encountered issues with applications using
MySQL Connector/J.
Questions
* 15.1: When I try to connect to the database with MySQL
Connector/J, I get the following exception:
SQLException: Server configuration denies access to data source
SQLState: 08001
VendorError: 0
What is going on? I can connect just fine with the MySQL
command-line client.
* 15.2: My application throws an SQLException 'No Suitable
Driver'. Why is this happening?
* 15.3: I'm trying to use MySQL Connector/J in an applet or
application and I get an exception similar to:
SQLException: Cannot connect to MySQL server on host:3306.
Is there a MySQL server running on the machine/port you
are trying to connect to?
(java.security.AccessControlException)
SQLState: 08S01
VendorError: 0
* 15.4: I have a servlet/application that works fine for a
day, and then stops working overnight
* 15.5: I'm trying to use JDBC 2.0 updatable result sets,
and I get an exception saying my result set is not
updatable.
* 15.6: I cannot connect to the MySQL server using
Connector/J, and I'm sure the connection parameters are
correct.
* 15.7: I am trying to connect to my MySQL server within my
application, but I get the following error and stack
trace:
java.net.SocketException
MESSAGE: Software caused connection abort: recv failed
STACKTRACE:
java.net.SocketException: Software caused connection abort: recv faile
d
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(Unknown Source)
at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:1392)
at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:1414)
at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:625)
at com.mysql.jdbc.Connection.createNewIO(Connection.java:1926)
at com.mysql.jdbc.Connection.<init>(Connection.java:452)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.ja
va:411)
* 15.8: My application is deployed through JBoss and I am
using transactions to handle the statements on the MySQL
database. Under heavy loads, I am getting an error and
stack trace, but these only occur after a fixed period of
heavy activity.
* 15.9: When using gcj, a java.io.CharConversionException
exception is raised when working with certain character
sequences.
* 15.10: Updating a table that contains a primary key
(http://dev.mysql.com/doc/refman/5.7/en/glossary.html#glo
s_primary_key) that is either FLOAT
(http://dev.mysql.com/doc/refman/5.7/en/floating-point-ty
pes.html) or compound primary key that uses FLOAT
(http://dev.mysql.com/doc/refman/5.7/en/floating-point-ty
pes.html) fails to update the table and raises an
exception.
* 15.11: You get an ER_NET_PACKET_TOO_LARGE
(http://dev.mysql.com/doc/refman/5.7/en/error-messages-se
rver.html#error_er_net_packet_too_large) exception, even
though the binary blob size you want to insert using JDBC
is safely below the max_allowed_packet
(http://dev.mysql.com/doc/refman/5.7/en/server-system-var
iables.html#sysvar_max_allowed_packet) size.
* 15.12: What should you do if you receive error messages
similar to the following: "Communications link failure -
Last packet sent to the server was X ms ago"?
* 15.13: Why does Connector/J not reconnect to MySQL and
re-issue the statement after a communication failure,
instead of throwing an Exception, even though I use the
autoReconnect connection string option?
* 15.14: How can I use 3-byte UTF8 with Connector/J?
* 15.15: How can I use 4-byte UTF8, utf8mb4 with
Connector/J?
* 15.16: Using useServerPrepStmts=false and certain
character encodings can lead to corruption when inserting
BLOBs. How can this be avoided?
Questions and Answers
15.1: When I try to connect to the database with MySQL
Connector/J, I get the following exception:
SQLException: Server configuration denies access to data source
SQLState: 08001
VendorError: 0
What is going on? I can connect just fine with the MySQL
command-line client.
MySQL Connector/J must use TCP/IP sockets to connect to
MySQL, as Java does not support Unix Domain Sockets.
Therefore, when MySQL Connector/J connects to MySQL, the
security manager in MySQL server will use its grant tables to
determine whether the connection is permitted.
You must add the necessary security credentials to the MySQL
server for this to happen, using the GRANT
(http://dev.mysql.com/doc/refman/5.7/en/grant.html) statement
to your MySQL Server. See GRANT Syntax
(http://dev.mysql.com/doc/refman/5.7/en/grant.html), for more
information.
Note
Testing your connectivity with the mysql command-line client
will not work unless you add the "host" flag, and use
something other than localhost for the host. The mysql
command-line client will use Unix domain sockets if you use
the special host name localhost. If you are testing
connectivity to localhost, use 127.0.0.1 as the host name
instead.
Warning
Changing privileges and permissions improperly in MySQL can
potentially cause your server installation to not have
optimal security properties.
15.2: My application throws an SQLException 'No Suitable
Driver'. Why is this happening?
There are three possible causes for this error:
* The Connector/J driver is not in your CLASSPATH, see
Chapter 3, "Connector/J Installation."
* The format of your connection URL is incorrect, or you
are referencing the wrong JDBC driver.
* When using DriverManager, the jdbc.drivers system
property has not been populated with the location of the
Connector/J driver.
15.3: I'm trying to use MySQL Connector/J in an applet or
application and I get an exception similar to:
SQLException: Cannot connect to MySQL server on host:3306.
Is there a MySQL server running on the machine/port you
are trying to connect to?
(java.security.AccessControlException)
SQLState: 08S01
VendorError: 0
Either you're running an Applet, your MySQL server has been
installed with the "skip-networking" option set, or your
MySQL server has a firewall sitting in front of it.
Applets can only make network connections back to the machine
that runs the web server that served the .class files for the
applet. This means that MySQL must run on the same machine
(or you must have some sort of port re-direction) for this to
work. This also means that you will not be able to test
applets from your local file system, you must always deploy
them to a web server.
MySQL Connector/J can only communicate with MySQL using
TCP/IP, as Java does not support Unix domain sockets. TCP/IP
communication with MySQL might be affected if MySQL was
started with the "skip-networking" flag, or if it is
firewalled.
If MySQL has been started with the "skip-networking" option
set (the Debian Linux package of MySQL server does this for
example), you need to comment it out in the file
/etc/mysql/my.cnf or /etc/my.cnf. Of course your my.cnf file
might also exist in the data directory of your MySQL server,
or anywhere else (depending on how MySQL was compiled for
your system). Binaries created by us always look in
/etc/my.cnf and datadir/my.cnf. If your MySQL server has been
firewalled, you will need to have the firewall configured to
allow TCP/IP connections from the host where your Java code
is running to the MySQL server on the port that MySQL is
listening to (by default, 3306).
15.4: I have a servlet/application that works fine for a day,
and then stops working overnight
MySQL closes connections after 8 hours of inactivity. You
either need to use a connection pool that handles stale
connections or use the autoReconnect parameter (see Section
5.1, "Driver/Datasource Class Names, URL Syntax and
Configuration Properties for Connector/J").
Also, catch SQLExceptions in your application and deal with
them, rather than propagating them all the way until your
application exits. This is just good programming practice.
MySQL Connector/J will set the SQLState (see
java.sql.SQLException.getSQLState() in your API docs) to
08S01 when it encounters network-connectivity issues during
the processing of a query. Attempt to reconnect to MySQL at
this point.
The following (simplistic) example shows what code that can
handle these exceptions might look like:
Example 15.1 Connector/J: Example of transaction with retry
logic
public void doBusinessOp() throws SQLException {
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
//
// How many times do you want to retry the transaction
// (or at least _getting_ a connection)?
//
int retryCount = 5;
boolean transactionCompleted = false;
do {
try {
conn = getConnection(); // assume getting this from a
// javax.sql.DataSource, or the
// java.sql.DriverManager
conn.setAutoCommit(false);
//
// Okay, at this point, the 'retry-ability' of the
// transaction really depends on your application logic,
// whether or not you're using autocommit (in this case
// not), and whether you're using transactional storage
// engines
//
// For this example, we'll assume that it's _not_ safe
// to retry the entire transaction, so we set retry
// count to 0 at this point
//
// If you were using exclusively transaction-safe tables,
// or your application could recover from a connection goi
ng
// bad in the middle of an operation, then you would not
// touch 'retryCount' here, and just let the loop repeat
// until retryCount == 0.
//
retryCount = 0;
stmt = conn.createStatement();
String query = "SELECT foo FROM bar ORDER BY baz";
rs = stmt.executeQuery(query);
while (rs.next()) {
}
rs.close();
rs = null;
stmt.close();
stmt = null;
conn.commit();
conn.close();
conn = null;
transactionCompleted = true;
} catch (SQLException sqlEx) {
//
// The two SQL states that are 'retry-able' are 08S01
// for a communications error, and 40001 for deadlock.
//
// Only retry if the error was due to a stale connection,
// communications problem or deadlock
//
String sqlState = sqlEx.getSQLState();
if ("08S01".equals(sqlState) || "40001".equals(sqlState))
{
retryCount -= 1;
} else {
retryCount = 0;
}
} finally {
if (rs != null) {
try {
rs.close();
} catch (SQLException sqlEx) {
// You'd probably want to log this...
}
}
if (stmt != null) {
try {
stmt.close();
} catch (SQLException sqlEx) {
// You'd probably want to log this as well...
}
}
if (conn != null) {
try {
//
// If we got here, and conn is not null, the
// transaction should be rolled back, as not
// all work has been done
try {
conn.rollback();
} finally {
conn.close();
}
} catch (SQLException sqlEx) {
//
// If we got an exception here, something
// pretty serious is going on, so we better
// pass it up the stack, rather than just
// logging it...
throw sqlEx;
}
}
}
} while (!transactionCompleted && (retryCount > 0));
}
Note
Use of the autoReconnect option is not recommended because
there is no safe method of reconnecting to the MySQL server
without risking some corruption of the connection state or
database state information. Instead, use a connection pool,
which will enable your application to connect to the MySQL
server using an available connection from the pool. The
autoReconnect facility is deprecated, and may be removed in a
future release.
15.5: I'm trying to use JDBC 2.0 updatable result sets, and I
get an exception saying my result set is not updatable.
Because MySQL does not have row identifiers, MySQL
Connector/J can only update result sets that have come from
queries on tables that have at least one primary key
(http://dev.mysql.com/doc/refman/5.7/en/glossary.html#glos_pr
imary_key), the query must select every primary key column,
and the query can only span one table (that is, no joins).
This is outlined in the JDBC specification.
Note that this issue only occurs when using updatable result
sets, and is caused because Connector/J is unable to
guarantee that it can identify the correct rows within the
result set to be updated without having a unique reference to
each row. There is no requirement to have a unique field on a
table if you are using UPDATE
(http://dev.mysql.com/doc/refman/5.7/en/update.html) or
DELETE (http://dev.mysql.com/doc/refman/5.7/en/delete.html)
statements on a table where you can individually specify the
criteria to be matched using a WHERE clause.
15.6: I cannot connect to the MySQL server using Connector/J,
and I'm sure the connection parameters are correct.
Make sure that the skip-networking
(http://dev.mysql.com/doc/refman/5.7/en/server-options.html#o
ption_mysqld_skip-networking) option has not been enabled on
your server. Connector/J must be able to communicate with
your server over TCP/IP; named sockets are not supported.
Also ensure that you are not filtering connections through a
firewall or other network security system. For more
information, see Can't connect to [local] MySQL server
(http://dev.mysql.com/doc/refman/5.7/en/can-not-connect-to-se
rver.html).
15.7: I am trying to connect to my MySQL server within my
application, but I get the following error and stack trace:
java.net.SocketException
MESSAGE: Software caused connection abort: recv failed
STACKTRACE:
java.net.SocketException: Software caused connection abort: recv faile
d
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(Unknown Source)
at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:1392)
at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:1414)
at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:625)
at com.mysql.jdbc.Connection.createNewIO(Connection.java:1926)
at com.mysql.jdbc.Connection.<init>(Connection.java:452)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.ja
va:411)
The error probably indicates that you are using a older
version of the Connector/J JDBC driver (2.0.14 or 3.0.x) and
you are trying to connect to a MySQL server with version 4.1x
or newer. The older drivers are not compatible with 4.1 or
newer of MySQL as they do not support the newer
authentication mechanisms.
It is likely that the older version of the Connector/J driver
exists within your application directory or your CLASSPATH
includes the older Connector/J package.
15.8: My application is deployed through JBoss and I am using
transactions to handle the statements on the MySQL database.
Under heavy loads, I am getting an error and stack trace, but
these only occur after a fixed period of heavy activity.
This is a JBoss, not Connector/J, issue and is connected to
the use of transactions. Under heavy loads the time taken for
transactions to complete can increase, and the error is
caused because you have exceeded the predefined timeout.
You can increase the timeout value by setting the
TransactionTimeout attribute to the TransactionManagerService
within the /conf/jboss-service.xml file (pre-4.0.3) or
/deploy/jta-service.xml for JBoss 4.0.3 or later. See
TransactionTimeout
(http://wiki.jboss.org/wiki/Wiki.jsp?page=TransactionTimeout)
within the JBoss wiki for more information.
15.9: When using gcj, a java.io.CharConversionException
exception is raised when working with certain character
sequences.
This is a known issue with gcj which raises an exception when
it reaches an unknown character or one it cannot convert. Add
useJvmCharsetConverters=true to your connection string to
force character conversion outside of the gcj libraries, or
try a different JDK.
15.10: Updating a table that contains a primary key
(http://dev.mysql.com/doc/refman/5.7/en/glossary.html#glos_pr
imary_key) that is either FLOAT
(http://dev.mysql.com/doc/refman/5.7/en/floating-point-types.
html) or compound primary key that uses FLOAT
(http://dev.mysql.com/doc/refman/5.7/en/floating-point-types.
html) fails to update the table and raises an exception.
Connector/J adds conditions to the WHERE clause during an
UPDATE (http://dev.mysql.com/doc/refman/5.7/en/update.html)
to check the old values of the primary key. If there is no
match, then Connector/J considers this a failure condition
and raises an exception.
The problem is that rounding differences between supplied
values and the values stored in the database may mean that
the values never match, and hence the update fails. The issue
will affect all queries, not just those from Connector/J.
To prevent this issue, use a primary key that does not use
FLOAT
(http://dev.mysql.com/doc/refman/5.7/en/floating-point-types.
html). If you have to use a floating point column in your
primary key, use DOUBLE
(http://dev.mysql.com/doc/refman/5.7/en/floating-point-types.
html) or DECIMAL
(http://dev.mysql.com/doc/refman/5.7/en/fixed-point-types.htm
l) types in place of FLOAT
(http://dev.mysql.com/doc/refman/5.7/en/floating-point-types.
html).
15.11: You get an ER_NET_PACKET_TOO_LARGE
(http://dev.mysql.com/doc/refman/5.7/en/error-messages-server
.html#error_er_net_packet_too_large) exception, even though
the binary blob size you want to insert using JDBC is safely
below the max_allowed_packet
(http://dev.mysql.com/doc/refman/5.7/en/server-system-variabl
es.html#sysvar_max_allowed_packet) size.
This is because the hexEscapeBlock() method in
com.mysql.jdbc.PreparedStatement.streamToBytes() may almost
double the size of your data.
15.12: What should you do if you receive error messages
similar to the following: "Communications link failure - Last
packet sent to the server was X ms ago"?
Generally speaking, this error suggests that the network
connection has been closed. There can be several root causes:
* Firewalls or routers may clamp down on idle connections
(the MySQL client/server protocol does not ping).
* The MySQL Server may be closing idle connections that
exceed the wait_timeout or interactive_timeout threshold.
To help troubleshoot these issues, the following tips can be
used. If a recent (5.1.13+) version of Connector/J is used,
you will see an improved level of information compared to
earlier versions. Older versions simply display the last time
a packet was sent to the server, which is frequently 0 ms
ago. This is of limited use, as it may be that a packet was
just sent, while a packet from the server has not been
received for several hours. Knowing the period of time since
Connector/J last received a packet from the server is useful
information, so if this is not displayed in your exception
message, it is recommended that you update Connector/J.
Further, if the time a packet was last sent/received exceeds
the wait_timeout or interactive_timeout threshold, this is
noted in the exception message.
Although network connections can be volatile, the following
can be helpful in avoiding problems:
* Ensure connections are valid when used from the
connection pool. Use a query that starts with /* ping */
to execute a lightweight ping instead of full query.
Note, the syntax of the ping needs to be exactly as
specified here.
* Minimize the duration a connection object is left idle
while other application logic is executed.
* Explicitly validate the connection before using it if the
connection has been left idle for an extended period of
time.
* Ensure that wait_timeout and interactive_timeout are set
sufficiently high.
* Ensure that tcpKeepalive is enabled.
* Ensure that any configurable firewall or router timeout
settings allow for the maximum expected connection idle
time.
Note
Do not expect to be able to reuse a connection without
problems, if it has being lying idle for a period. If a
connection is to be reused after being idle for any length of
time, ensure that you explicitly test it before reusing it.
15.13: Why does Connector/J not reconnect to MySQL and
re-issue the statement after a communication failure, instead
of throwing an Exception, even though I use the autoReconnect
connection string option?
There are several reasons for this. The first is
transactional integrity. The MySQL Reference Manual states
that "there is no safe method of reconnecting to the MySQL
server without risking some corruption of the connection
state or database state information". Consider the following
series of statements for example:
conn.createStatement().execute(
"UPDATE checking_account SET balance = balance - 1000.00 WHERE custo
mer='Smith'");
conn.createStatement().execute(
"UPDATE savings_account SET balance = balance + 1000.00 WHERE custom
er='Smith'");
conn.commit();
Consider the case where the connection to the server fails
after the UPDATE to checking_account. If no exception is
thrown, and the application never learns about the problem,
it will continue executing. However, the server did not
commit the first transaction in this case, so that will get
rolled back. But execution continues with the next
transaction, and increases the savings_account balance by
1000. The application did not receive an exception, so it
continued regardless, eventually committing the second
transaction, as the commit only applies to the changes made
in the new connection. Rather than a transfer taking place, a
deposit was made in this example.
Note that running with autocommit enabled does not solve this
problem. When Connector/J encounters a communication problem,
there is no means to determine whether the server processed
the currently executing statement or not. The following
theoretical states are equally possible:
* The server never received the statement, and therefore no
related processing occurred on the server.
* The server received the statement, executed it in full,
but the response was not received by the client.
If you are running with autocommit enabled, it is not
possible to guarantee the state of data on the server when a
communication exception is encountered. The statement may
have reached the server, or it may not. All you know is that
communication failed at some point, before the client
received confirmation (or data) from the server. This does
not only affect autocommit statements though. If the
communication problem occurred during Connection.commit(),
the question arises of whether the transaction was committed
on the server before the communication failed, or whether the
server received the commit request at all.
The second reason for the generation of exceptions is that
transaction-scoped contextual data may be vulnerable, for
example:
* Temporary tables.
* User-defined variables.
* Server-side prepared statements.
These items are lost when a connection fails, and if the
connection silently reconnects without generating an
exception, this could be detrimental to the correct execution
of your application.
In summary, communication errors generate conditions that may
well be unsafe for Connector/J to simply ignore by silently
reconnecting. It is necessary for the application to be
notified. It is then for the application developer to decide
how to proceed in the event of connection errors and
failures.
15.14: How can I use 3-byte UTF8 with Connector/J?
To use 3-byte UTF8 with Connector/J set
characterEncoding=utf8 and set useUnicode=true in the
connection string.
15.15: How can I use 4-byte UTF8, utf8mb4 with Connector/J?
To use 4-byte UTF8 with Connector/J configure the MySQL
server with character_set_server=utf8mb4. Connector/J will
then use that setting as long as characterEncoding has not
been set in the connection string. This is equivalent to
autodetection of the character set.
15.16: Using useServerPrepStmts=false and certain character
encodings can lead to corruption when inserting BLOBs. How
can this be avoided?
When using certain character encodings, such as SJIS, CP932,
and BIG5, it is possible that BLOB data contains characters
that can be interpreted as control characters, for example,
backslash, '\'. This can lead to corrupted data when
inserting BLOBs into the database. There are two things that
need to be done to avoid this:
1. Set the connection string option useServerPrepStmts to
true.
2. Set SQL_MODE to NO_BACKSLASH_ESCAPES.
Chapter 16 Known Issues and Limitations
The following are some known issues and limitations for MySQL
Connector/J:
* When Connector/J retrieves timestamps for a daylight
saving time (DST) switch day using the getTimeStamp()
method on the result set, some of the returned values
might be wrong. The errors can be avoided by using the
following connection options when connecting to a
database:
useTimezone=true
useLegacyDatetimeCode=false
serverTimezone=UTC
Chapter 17 Connector/J Support
17.1 Connector/J Community Support
Oracle provides assistance to the user community by means of
its mailing lists. For Connector/J related issues, you can
get help from experienced users by using the MySQL and Java
mailing list. Archives and subscription information is
available online at http://lists.mysql.com/java.
For information about subscribing to MySQL mailing lists or
to browse list archives, visit http://lists.mysql.com/. See
MySQL Mailing Lists
(http://dev.mysql.com/doc/refman/5.7/en/mailing-lists.html).
Community support from experienced users is also available
through the JDBC Forum (http://forums.mysql.com/list.php?39).
You may also find help from other users in the other MySQL
Forums, located at http://forums.mysql.com. See MySQL
Community Support at the MySQL Forums
(http://dev.mysql.com/doc/refman/5.7/en/forums.html).
17.2 How to Report Connector/J Bugs or Problems
The normal place to report bugs is http://bugs.mysql.com/,
which is the address for our bugs database. This database is
public, and can be browsed and searched by anyone. If you log
in to the system, you will also be able to enter new reports.
If you find a sensitive security bug in MySQL Server, please
let us know immediately by sending an email message to
secalert_us@oracle.com. Exception: Support customers should
report all problems, including security bugs, to Oracle
Support at http://support.oracle.com/.
Writing a good bug report takes patience, but doing it right
the first time saves time both for us and for yourself. A
good bug report, containing a full test case for the bug,
makes it very likely that we will fix the bug in the next
release.
This section will help you write your report correctly so
that you do not waste your time doing things that may not
help us much or at all.
If you have a repeatable bug report, please report it to the
bugs database at http://bugs.mysql.com/. Any bug that we are
able to repeat has a high chance of being fixed in the next
MySQL release.
To report other problems, you can use one of the MySQL
mailing lists.
Remember that it is possible for us to respond to a message
containing too much information, but not to one containing
too little. People often omit facts because they think they
know the cause of a problem and assume that some details do
not matter.
A good principle is this: If you are in doubt about stating
something, state it. It is faster and less troublesome to
write a couple more lines in your report than to wait longer
for the answer if we must ask you to provide information that
was missing from the initial report.
The most common errors made in bug reports are (a) not
including the version number of Connector/J or MySQL used,
and (b) not fully describing the platform on which
Connector/J is installed (including the JVM version, and the
platform type and version number that MySQL itself is
installed on).
This is highly relevant information, and in 99 cases out of
100, the bug report is useless without it. Very often we get
questions like, "Why doesn't this work for me?" Then we find
that the feature requested wasn't implemented in that MySQL
version, or that a bug described in a report has already been
fixed in newer MySQL versions.
Sometimes the error is platform-dependent; in such cases, it
is next to impossible for us to fix anything without knowing
the operating system and the version number of the platform.
If at all possible, create a repeatable, standalone testcase
that doesn't involve any third-party classes.
To streamline this process, we ship a base class for
testcases with Connector/J, named
'com.mysql.jdbc.util.BaseBugReport'. To create a testcase for
Connector/J using this class, create your own class that
inherits from com.mysql.jdbc.util.BaseBugReport and override
the methods setUp(), tearDown() and runTest().
In the setUp() method, create code that creates your tables,
and populates them with any data needed to demonstrate the
bug.
In the runTest() method, create code that demonstrates the
bug using the tables and data you created in the setUp
method.
In the tearDown() method, drop any tables you created in the
setUp() method.
In any of the above three methods, use one of the variants of
the getConnection() method to create a JDBC connection to
MySQL:
* getConnection() - Provides a connection to the JDBC URL
specified in getUrl(). If a connection already exists,
that connection is returned, otherwise a new connection
is created.
* getNewConnection() - Use this if you need to get a new
connection for your bug report (that is, there is more
than one connection involved).
* getConnection(String url) - Returns a connection using
the given URL.
* getConnection(String url, Properties props) - Returns a
connection using the given URL and properties.
If you need to use a JDBC URL that is different from
'jdbc:mysql:///test', override the method getUrl() as well.
Use the assertTrue(boolean expression) and assertTrue(String
failureMessage, boolean expression) methods to create
conditions that must be met in your testcase demonstrating
the behavior you are expecting (vs. the behavior you are
observing, which is why you are most likely filing a bug
report).
Finally, create a main() method that creates a new instance
of your testcase, and calls the run method:
public static void main(String[] args) throws Exception {
new MyBugReport().run();
}
Once you have finished your testcase, and have verified that
it demonstrates the bug you are reporting, upload it with
your bug report to http://bugs.mysql.com/.
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