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.
Document generated on: 2014-10-17 (revision: 40474)
Table of Contents
This manual describes how to install, configure, and develop database applications using MySQL Connector/J, the JDBC driver for communicating with MySQL servers.
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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.
MySQL Connector/J is a JDBC Type 4 driver. Different versions are available that are compatible with the JDBC 3.0 and JDBC 4.0 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, Spring's JDBC templates or Ibatis SQL Maps to reduce the amount of JDBC code for you to debug, tune, secure, and maintain.
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”.
There are currently four versions of MySQL Connector/J available:
Connector/J 5.1 is the Type 4 pure Java JDBC driver, which
conforms to the JDBC 3.0 and JDBC 4.0 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 the
JDBC-4.0 XML processing, per connection client information,
NCHAR,
NVARCHAR and
NCLOB 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, 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.
For details of new features and bug fixes in each Connector/J release, see the MySQL Connector/J Release Notes.
The following table summarizes what version of Java RTE 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 | Java RTE required | JDK required (to build source code) |
|---|---|---|
| 5.1 | 1.5.x, 1.6.x, 1.7.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 the Development Source Tree”), 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.
Java 1.7 support requires Connector/J 5.1.21 and higher. 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.
Table of Contents
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.
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-.
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
version-bin-g.jarsrc/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.
Once you have extracted the distribution archive, you can
install the driver by placing
mysql-connector-java-in your classpath, either by adding the full path to
it to your version-bin.jar
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 Mac 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:$CLASSPATH # C shell (csh, tcsh): shell> setenv CLASSPATH /path/mysql-connector-java-ver-bin.jar:$CLASSPATH
Within Windows 2000, Windows XP, Windows Server 2003 and Windows Vista, 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 8.1, “Configuring Load Balancing with Connector/J”,
and
Section 8.2, “Configuring Failover with Connector/J”.
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.
The various MysqlDataSource classes
support the following parameters (through standard set
mutators):
user
password
serverName (see the previous section
about fail-over hosts)
databaseName
port
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.
In Connector/J 5.0.x and earlier, the alias for a table in
a SELECT 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 was 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.
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
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, 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 column will now return
the address of the byte[] array that
represents it, instead of a String
representation of the BLOB.
BLOB 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 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-
is shipped alongside the normal binary jar file that is
named
version-bin-g.jarmysql-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.
Read this section only if you are interested in helping us test our new code. To just get MySQL Connector/J up and running on your system, use a standard binary release distribution.
The requirements and steps for installing Connector/J 5.1.34 and later and 5.1.33 and earlier from source are different. Check the section below that is relevant for the version you desire.
Installing Connector/J 5.1.34 or later from the development source tree. To install MySQL Connector/J from the development source tree, make sure that you have the following software on your system:
A Bazaar client, to check out the sources from our Launchpad repository (available from http://bazaar-vcs.org/).
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-Install).
The required jar files from the
Hibernate ORM 4.1.12 Final release bundle, which is
available at
http://sourceforge.net/projects/hibernate/files/hibernate4/.
To check out and compile a specific branch of MySQL Connector/J, follow these steps:
Check out the latest code from the branch that you want with one of the following commands.
The source code repository for MySQL Connector/J is located on Launchpad at https://code.launchpad.net/connectorj. To check out the latest development branch, use:
shell> bzr branch lp:connectorj
This creates a connectorj subdirectory
in the current directory that contains the latest sources
for the requested branch.
To check out the code for the latest release in the 5.1 series, use:
shell> bzr branch lp:connectorj/5.1
This creates a 5.1 subdirectory in the
current directory containing the latest 5.1 code.
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.
Place the required junit.jar file in a
separate directory—for example,
/home/username/ant-extralibs.
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 4.1.2 Final release bundle.
Change your current working directory to either the
connectorj or 5.1
directory, depending on which branch you intend to build.
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_1.5com.mysql.jdbc.jdk6=path_to_jdk_1.6com.mysql.jdbc.extra.libs=path_to_folder_for_extra_libraries
Alternatively, you can set the values of those properties
through the Ant -D options.
Issue the following command to compile the driver and create
a .jar file suitable for installation:
shell> ant dist
This creates a build directory in the
current directory, where all build output will go. A
directory is created in the build
directory that includes the version number of the sources
you are building from. This directory contains the sources,
compiled .class files, and a
.jar file suitable for deployment. For
more information and other possible targets, including those
that create a fully packaged distribution, issue the
following command:
shell> ant -projecthelp
A newly created .jar file containing
the JDBC driver will be placed in the directory
build/mysql-connector-java-.
Install the newly created JDBC driver as you would install a
binary version.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
Installing Connector/J 5.1.33 or earlier from the development source tree. To install MySQL Connector/J from the development source tree, make sure that you have the following software on your system:
A Bazaar client, to check out the sources from our Launchpad repository (available from http://bazaar-vcs.org/).
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-contrib/1.0b3/) and JUnit (available from https://github.com/junit-team/junit/wiki/Download-and-Install) libraries.
The required jar files from the
Hibernate ORM 4.1.12 Final release bundle, which is
available at
http://sourceforge.net/projects/hibernate/files/hibernate4/.
To check out and compile a specific branch of MySQL Connector/J, follow these steps:
Check out the code for the Connector/J revision you want. The source code repository for MySQL Connector/J is located on Launchpad at https://code.launchpad.net/connectorj. Check out the code for revision 5.1.xx by using the following Bazaar command, specifying the tag revision for it:
shell> bzr branch connectorj/5.1 -r tag:5.1.xx
This creates a 5.1 subdirectory in the
current directory containing the 5.1.xx code.
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.
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.
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 4.1.2 Final release bundle.
Change your current working directory to either the
connectorj or 5.1
directory, depending on which branch you intend to build.
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.
Issue the following command to compile the driver and create
a .jar file suitable for installation:
shell> ant dist
This creates a build directory in the
current directory, where all build output will go. A
directory is created in the build
directory that includes the version number of the sources
you are building from. This directory contains the sources,
compiled .class files, and a
.jar file suitable for deployment. For
more information and other possible targets, including those
that create a fully packaged distribution, issue the
following command:
shell> ant -projecthelp
A newly created .jar file containing
the JDBC driver will be placed in the directory
build/mysql-connector-java-.
Install the newly created JDBC driver as you would install a
binary version.jar file you download from
MySQL by following the instructions given in
Section 3.2, “Installing the Driver and Configuring the CLASSPATH”.
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 6.6, “Connector/J: Setting CallableStatement input
parameters”
Example 6.7, “Connector/J: Retrieving results and output parameter values”
Example 6.9, “Connector/J: Retrieving AUTO_INCREMENT column values
using SELECT LAST_INSERT_ID()”
Example 6.10, “Connector/J: Retrieving AUTO_INCREMENT column values
in Updatable ResultSets”
Example 7.1, “Connector/J: Using a connection pool with a J2EE application server”
Example 15.1, “Connector/J: Example of transaction with retry logic”
Table of Contents
This section of the manual contains reference material for MySQL 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 otherwise configuring software to use MySQL Connector/J.
The JDBC URL format for MySQL Connector/J is as follows, with items in square brackets ([, ]) being optional:
jdbc:mysql://[host][,failoverhost...][:port]/[database] » [?propertyName1][=propertyValue1][&propertyName2][=propertyValue2]...
If the host name is not specified, it defaults to
127.0.0.1. If the port is not specified, it
defaults to 3306, the default port number for
MySQL servers.
jdbc:mysql://[host:port],[host:port].../[database] » [?propertyName1][=propertyValue1][&propertyName2][=propertyValue2]...
Here is a sample connection URL:
jdbc:mysql://localhost:3306/sakila?profileSQL=true
For IPv6 connections, use this alternative syntax to specify
hosts in the URL,
address=(.
Supported keys are:
key=value)
(protocol=tcp), or
(protocol=pipe) for named pipes on
Windows.
(path=
for named pipes.
path_to_pipe)
(host=
for TCP connections.
hostname)
(port=
for TCP connections.
port_number)
For example:
jdbc:mysql://address=(protocol=tcp)(host=localhost)(port=3306)(user=test)/db
Any other parameters are treated as host-specific properties that follow the conventions of the JDBC URL properties. This now allows per-host overrides of any configuration property for multi-host connections (that is, when using failover, load balancing, or replication). Limit the overrides to user, password, network timeouts and statement and metadata cache sizes; the results of other per-host overrides are not defined.
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
) 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.
dbname.tablename.colname
FROM dbname.tablename...
Always use the Connection.setCatalog()
method to specify the desired database in JDBC applications,
rather than the USE
statement.
database
MySQL Connector/J has failover support. This enables the driver
to fail over to any number of slave hosts and still perform
read-only queries. Failover only happens when the connection is
in an autoCommit(true) state, because
failover cannot happen reliably when a
transaction is in
progress. Most application servers and connection pools set
autoCommit to true at the
end of every transaction/connection use.
The failover functionality has the following behavior:
If the URL property autoReconnect is
false: Failover only happens at
connection initialization, and failback occurs when the
driver determines that the first host has become available
again.
If the URL property autoReconnect is
true: Failover happens when the driver
determines that the connection has failed (checked before
every query), and falls back to the
first host when it determines that the host has become
available again (after
queriesBeforeRetryMaster queries have
been issued).
In either case, whenever you are connected to a “failed-over” server, the connection is set to read-only state, so queries that attempt to modify data will throw exceptions (the query will never be processed by the MySQL server).
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.MysqlConnectionPoolDataSource
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 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, 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 master 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 master. Defaults to 50. Default: 50 Since version: 3.0.2 |
secondsBeforeRetryMaster How long should the driver wait, when failed over, before attempting Default: 30 Since version: 3.0.2 |
allowMasterDownConnections Should replication-aware driver establish connections to slaves when connection to master servers cannot be established at initial connection? Defaults to 'false', which will cause SQLException when configured master hosts are all unavailable when establishing a new replication-aware Connection. Default: false Since version: 5.1.27 |
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), defaults to '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: 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 |
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 platform character set, which works for ISO8859_1 (i.e. "latin1") passwords. For passwords in other character encodings, the encoding will have to be specified with this property, 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 |
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 |
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 will 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 |
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.getString()) Default: false Since version: 3.1.7 |
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: 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 |
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 NT, Windows 2000, or Windows XP using the
NamedPipeSocketFactory as a plugin-socket
factory using the socketFactory property. 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, use:
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.
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-
JAR file. For example, the Connector/J 5.1.9 driver includes
the following configuration properties files:
version-bin.jar
$ 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.
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
useDirectRowUnpack=false
autoReconnect=true failOverReadOnly=false roundRobinLoadBalance=true
useDynamicCharsetInfo=false alwaysSendSetIsolation=false useLocalSessionState=true autoReconnect=true
profileSQL=true gatherPerfMetrics=true useUsageAdvisor=true logSlowQueries=true explainSlowQueries=true
cachePrepStmts=true cacheCallableStmts=true cacheServerConfiguration=true useLocalSessionState=true elideSetAutoCommits=true alwaysSendSetIsolation=false enableQueryTimeouts=false
useUnbufferedInput=false useReadAheadInput=false maintainTimeStats=false
MySQL Connector/J, as a rigorous implementation of the JDBC API, 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 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.
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
information
(getImportedKeys()/getExportedKeys()
and getCrossReference()) is only
available from InnoDB tables.
The driver uses SHOW CREATE
TABLE 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
statement. In the case of
setQueryTimeout(), the implementation
creates an additional thread to handle the timeout
functionality.
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.
The MySQL statement
KILL QUERY
(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 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 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.
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 statement.
This method returns NULL if no such
stream has been set using
setLocalInfileInputStream().
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.
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 |
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
java.sql.Types classes see
Java
2 Platform Types.
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 |
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().
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.
The character encoding between client and server is
automatically detected upon connection. You specify the encoding
on the server using the
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.
For example, to use 4-byte UTF-8 character sets with
Connector/J, configure the MySQL server with
character_set_server=utf8mb4,
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 |
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.
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://developer.java.sun.com/developer/bugParade/bugs/4273544.html
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 Configuring MySQL for SSL.
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=MySQL AB, L=Orenburg, ST=Some-State, C=RU
Issuer: EMAILADDRESS=walrus@example.com, CN=Walrus,
O=MySQL AB, 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 mysqlClientCertificate
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]: MySQL AB
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=MySQL AB,
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.
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 for more information. Connector/J implements the same cleartext authentication method as in The Cleartext Client-Side Authentication Plugin.
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.
See Section 8.3, “Master/Slave Replication with ReplicationConnection” for details on the topic.
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 | 41000 | 41000 |
| 1207 | ER_READ_ONLY_TRANSACTION | 25000 | 25000 |
| 1211 | ER_NO_PERMISSION_TO_CREATE_USER | 42000 | 42000 |
| 1213 | ER_LOCK_DEADLOCK | 41000 | 41000 |
| 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 |
Table of Contents
This section provides some general JDBC background.
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 section
Section 6.1, “Connecting to MySQL Using the JDBC DriverManager
Interface”
before working with these examples.
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=monty&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.
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 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 or an
UPDATE/INSERT,
then you can use the execute(String SQL)
method. This method will return true if the SQL query was a
SELECT, or false if it was an
UPDATE,
INSERT, or
DELETE statement. If the
statement was a SELECT query, you
can retrieve the results by calling the
getResultSet() method. If the statement was
an UPDATE,
INSERT, or
DELETE 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 previous 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;
}
}
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 http://dev.mysql.com/doc/mysql/en/stored-routines.html.
Connector/J exposes stored procedure functionality through
JDBC's CallableStatement interface.
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:
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");
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.
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);
...
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);
...
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
...
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 to a table that had an
AUTO_INCREMENT key. Using the MySQL-specific
method call isn't portable, and issuing a
SELECT 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.
Connection pooling is a technique of creating and managing a pool of connections that are ready for use by any thread that needs them. Connection pooling can greatly increase the performance of your Java application, while reducing overall resource usage.
Most applications only need a thread to have access to a JDBC connection when they are actively processing a transaction, 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.
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 lead to unpredictable behavior under load.
Sun has standardized the concept of connection pooling in JDBC 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.
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 Sun'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.
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:
Before the pool returns a connection to the application.
When the application returns a connection to the pool.
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.
Table of Contents
The following sections discuss a number of topics that involve multi-host connections, namely: server load-balancing, fail-over, 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.
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.
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.
There are two connection string options 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 string options, 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, ClassNotFoundException {
Class.forName("com.mysql.jdbc.Driver");
return DriverManager.getConnection(URL, "root", "");
}
static void executeSimpleTransaction(Connection c, int conn, int trans){
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
. 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 8.2, “Configuring Failover with Connector/J”.
Connector/J provides a useful load-balancing implementation for
Cluster or multi-master deployments, as explained in
Section 8.1, “Configuring Load Balancing with Connector/J”.
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:
At transaction boundaries (transactions are explicitly committed or rolled back).
A communication exception (SQL State starting with "08") is encountered.
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.SQLTransientConnectionException
While the three fail-over 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.
This section describe a number of features of Connector/J's support for replication-aware deployments.
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), this
replication-aware connection will use one of the slave
connections, which are load-balanced per-vm using a round-robin
scheme (a given connection is sticky to a slave unless that
slave is removed from service). 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 one
// from the list
//
conn.setReadOnly(true);
ResultSet rs =
conn.createStatement().executeQuery("SELECT a,b FROM alt_table");
.......
}
}
Consider investigating 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).
Since Connector/J 5.1.27, multi-master replication topographies are supported. They can be specified using the following host definition syntax:
address=(host=hostname)(port=3306)(type=[master|slave])
The definition described above 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 different properties for specific hosts,
which is just an expansion of the legacy URL syntax with the
property type=[master|slave]; for example:
jdbc:mysql://address=(type=master)(host=master1host),address=(type=master)(host=master2host),address=(type=slave)(host=slave1host)/db
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 8.1, “Configuring Load Balancing with Connector/J”.
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.
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
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.
When Connector/J is started with
replicationEnableJMX=true, 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) throws 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);
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.
The following instructions are based on the instructions for Tomcat-5.x, available at http://tomcat.apache.org/tomcat-5.5-doc/jndi-datasource-examples-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 ' SQL state: null
Note that the auto-loading of drivers having the
META-INF/service/java.sql.Driver class in
JDBC 4.0 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.
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>
Table of Contents
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). 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.DriverManagerDataSource">
<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.PropertyPlaceholderConfigurer">
<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.Code " +
"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.
Spring makes extensive use of the Template method design pattern
(see
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 parameters
NamedParameterJdbcTemplate template =
new NamedParameterJdbcTemplate(dataSource);
// A java.util.Map is used to provide values for the parameters
Map params = new HashMap();
params.put("country", cntryCode);
// We query for an Object and specify what class we are expecting
return (String)template.queryForObject(queryString, params, String.class);
}
/**
* A JavaBean setter-style method to allow Spring to inject the data 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.
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.DataSourceTransactionManager">
<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.
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. 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"/>
Table of Contents
This section explains how to use MySQL Connector/J with GlassFish ™ Server Open Source Edition 3.0.1. GlassFish can be downloaded from the GlassFish website.
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/libmysql-connector-java-5.1.30-bin.jar to
C:\.
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.
glassfish-install-path\domains\domain-name\lib
You are now ready to create JDBC Connection Pools and JDBC Resources.
Creating a Connection Pool
In the GlassFish Administration Console, using the navigation tree navigate to Resources, JDBC, Connection Pools.
In the JDBC Connection Pools frame click . You will enter a two step wizard.
In the Name field under General
Settings enter the name for the connection pool,
for example enter MySQLConnPool.
In the Resource Type field, select
javax.sql.DataSource from the drop-down
listbox.
In the Database Vendor field, select
MySQL from the drop-down listbox. Click
to go to the next page of the
wizard.
You can accept the default settings for General Settings, Pool Settings and Transactions for this example. Scroll down to Additional Properties.
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.
Click 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.
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.
To test your connection pool click the 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 . 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 to create the new JDBC resource. The JDBC Resources frame will list all available JDBC Resources.
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:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://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 Application 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:
In the navigation tree, navigate to Applications - the Applications frame will be displayed. Click .
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.
Now select the application type from the
Type drop-down listbox, which in this
example is Web application.
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.
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 nto 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.
Whe 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 HelloWebServlet.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.
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. For instructions on how to use Connector/J with MySQL Fabric, see Using Connector/J with MySQL Fabric.
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 failed 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.java: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 that is
either FLOAT or compound
primary key that uses FLOAT
fails to update the table and raises an exception.
15.11:
You get an
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 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 statement to your MySQL
Server. See GRANT Syntax, for more information.
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.
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
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 going
// 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));
}
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, 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 or
DELETE 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 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.
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 failed 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.java: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
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 that is
either FLOAT or compound
primary key that uses FLOAT
fails to update the table and raises an exception.
Connector/J adds conditions to the WHERE
clause during an UPDATE 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. If you have to use a
floating point column in your primary key, use
DOUBLE or
DECIMAL types in place of
FLOAT.
15.11:
You get an
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 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.
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 customer='Smith'"); conn.createStatement().execute( "UPDATE savings_account SET balance = balance + 1000.00 WHERE customer='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:
Set the connection string option
useServerPrepStmts to
true.
Set SQL_MODE to
NO_BACKSLASH_ESCAPES.
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
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.
Community support from experienced users is also available through the JDBC Forum. 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.
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/.
Table of Contents
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