Tomcat 结合Atomikos 实现JTA

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Tomcat下配置Atomikos实现JTA

Tomcat作为一款经典的Web服务器，在开发、测试和生产环境中得到了广泛的使用。但Tomcat毕竟不是Java EE服务器，因此在EJB，JTA方面并没有提供支持。本文讲述了Tomcat使用Atomikos实现JTA的一种方法。

在Tomcat中使用JTA，可以将Atomikos部署在Tomcat中，使用Tomcat支持的数据源；也可以在项目中配置，利用Spring配置好数据源、连接池、事务管理器等等。两种方式各有特点，本文只介绍Tomcat与Atomikos的集成，集成后Tomcat可以对外提供JTA的事务管理器和数据源。

在使用Atomikos之前，我们也曾使用过JOTM，不过在高并发的情况下，JOTM频频出错，最后不得不放弃，通过测试，发现Atomikos性能和稳定性都不错。

我们使用了Atomikos最新的4.04版本，Jar包的获取可以从maven的配置库中得到，链接地址：http://mvnrepository.com/artifact/com.atomikos

如果不使用Hibernate，需要的包包括：

atomikos-util.jar,jta.jar,transactions.jar,transactions-api.jar,transactions-jdbc.jar,

transactions-jta.jar

配置步骤如下：

Step 1：将这些jar 拷贝到tomcat 的lib 目录中。要实现Tomcat与Atomikos集成，还需要一个集成包，这个集成包里面有两个class,可以自己参考实现，也可以使用官方提供的jar包，最新的是atomikos-integration-extension-3.7.2.jar

Step2：在tomcat/config/server.xml中增加一个监听器

Step3：在tomcat/config/context.xml中增加数据源和相关的事务管理器，下面是一个参考的例子，参数酌情修改

<Resource name="jdbc/DS_MYSQL"

auth="Container"

type="com.atomikos.jdbc.AtomikosDataSourceBean"

uniqueResourceName="jdbc/DS_MYSQL"

xaDataSourceClassName="com.mysql.jdbc.jdbc2.optional.MysqlXADataSource"

xaProperties.databaseName="db_test"

xaProperties.serverName="localhost"

xaProperties.port="3306"

xaProperties.user="root"

xaProperties.password="root"

maxPoolSize="200"

xaProperties.url="jdbc:mysql://localhost:3306/db_test?characterEncoding=UTF8"

factory="com.atomikos.tomcat.EnhancedTomcatAtomikosBeanFactory" />

<Resource name="UserTransaction"

auth="Container"

type="javax.transaction.UserTransaction" />

Step4：在tomcat/lib目录下增加一个jta.properties文件，设置Atomikos事务相关的参数，否则将使用默认的配置参数，一些并发事务数（默认50个），超时时间等都需要调整，下面给出了文件中的一些参数配置，参数解释请查阅官方文档：https://www.atomikos.com/Documentation/JtaProperties

# SAMPLE PROPERTIES FILE FOR THE TRANSACTION SERVICE

# THIS FILE ILLUSTRATES THE DIFFERENT SETTINGS FOR THE TRANSACTION MANAGER

# UNCOMMENT THE ASSIGNMENTS TO OVERRIDE DEFAULT VALUES;

# Required: factory implementation class of the transaction core.

# NOTE: there is no default for this, so it MUST be specified!

com.atomikos.icatch.service=com.atomikos.icatch.standalone.UserTransactionServiceFactory

# Set base name of file where messages are output

# (also known as the 'console file').

# com.atomikos.icatch.console_file_name = tm.out

# Size limit (in bytes) for the console file;

# negative means unlimited.

# com.atomikos.icatch.console_file_limit=-1

# For size-limited console files, this option

# specifies a number of rotating files to

# maintain.

# com.atomikos.icatch.console_file_count=1

# Set the number of log writes between checkpoints

# com.atomikos.icatch.checkpoint_interval=500

# Set output directory where console file and other files are to be put

# make sure this directory exists!

# com.atomikos.icatch.output_dir = ./

# Set directory of log files; make sure this directory exists!

# com.atomikos.icatch.log_base_dir = ./

# Set base name of log file

# this name will be used as the first part of

# the system-generated log file name

# com.atomikos.icatch.log_base_name = tmlog

# Set the max number of active local transactions

# or -1 for unlimited.

# com.atomikos.icatch.max_actives = 50

# Set the default timeout (in milliseconds) for local transactions

# com.atomikos.icatch.default_jta_timeout = 10000

# Set the max timeout (in milliseconds) for local transactions

# com.atomikos.icatch.max_timeout = 300000

# The globally unique name of this transaction manager process

# override this value with a globally unique name

# com.atomikos.icatch.tm_unique_name = tm

# Do we want to use parallel subtransactions? JTA's default

# is NO for J2EE compatibility

# com.atomikos.icatch.serial_jta_transactions=true

# If you want to do explicit resource registration then

# you need to set this value to false.

# com.atomikos.icatch.automatic_resource_registration=true

# Set this to WARN, INFO or DEBUG to control the granularity

# of output to the console file.

# com.atomikos.icatch.console_log_level=WARN

# Do you want transaction logging to be enabled or not?

# If set to false, then no logging overhead will be done

# at the risk of losing data after restart or crash.

# com.atomikos.icatch.enable_logging=true

# Should two-phase commit be done in (multi-)threaded mode or not?

# Set this to false if you want commits to be ordered according

# to the order in which resources are added to the transaction.

# NOTE: threads are reused on JDK 1.5 or higher.

# For JDK 1.4, thread reuse is enabled as soon as the

# concurrent backport is in the classpath - see

# http://mirrors.ibiblio.org/pub/mirrors/maven2/backport-util-concurrent/backport-util-concurrent/

# com.atomikos.icatch.threaded_2pc=false

# Should shutdown of the VM trigger shutdown of the transaction core too?

# com.atomikos.icatch.force_shutdown_on_vm_exit=false

Atomikos中参数的默认值在transactions.jar中定义，transactions-default.properties,具体参数如下：

com.atomikos.icatch.enable_logging=true

com.atomikos.icatch.force_shutdown_on_vm_exit=false

com.atomikos.icatch.automatic_resource_registration=true

com.atomikos.icatch.checkpoint_interval=500

com.atomikos.icatch.serial_jta_transactions=true

com.atomikos.icatch.default_jta_timeout=10000

com.atomikos.icatch.max_timeout=300000

com.atomikos.icatch.log_base_dir=./

com.atomikos.icatch.threaded_2pc=false

com.atomikos.icatch.max_actives=50

com.atomikos.icatch.log_base_name=tmlog

java.naming.factory.initial=com.sun.jndi.rmi.registry.RegistryContextFactory

com.atomikos.icatch.client_demarcation=false

java.naming.provider.url=rmi://localhost:1099

com.atomikos.icatch.rmi_export_class=none

com.atomikos.icatch.trust_client_tm=false

com.atomikos.icatch.forget_orphaned_log_entries_delay=86400000

com.atomikos.icatch.recovery_delay=${com.atomikos.icatch.default_jta_timeout}

com.atomikos.icatch.oltp_max_retries=5

com.atomikos.icatch.oltp_retry_interval=10000

com.atomikos.icatch.allow_subtransactions=true

配置完以上四个步骤，Tomcat的集成就算完成了，项目中可以使用Spring来关联数据源和事务管理器，参考配置如下：

<beanclass="org.springframework.jndi.JndiTemplate"id="jndiTemplate"/>

<beanclass="org.springframework.jndi.JndiObjectFactoryBean"id="dataSource">

<propertyname="jndiName">

<value>java:comp/env/jdbc/DS_MYSQL</value>

</property>

<propertyname="jndiTemplate">

<refbean="jndiTemplate"/>

</property>

</bean>

<beanid="jdbcTemplate"class="org.springframework.jdbc.core.JdbcTemplate">

<propertyname="dataSource">

<refbean="dataSource"/>

</property>

</bean>

<beanclass="org.springframework.jndi.JndiObjectFactoryBean"id="userTransaction">

<propertyname="jndiName">

<value>java:comp/UserTransaction</value>

</property>

<propertyname="jndiTemplate">

<refbean="jndiTemplate"/>

</property>

</bean>

<beanid="atomikosTransactionManager"class="com.atomikos.icatch.jta.UserTransactionManager"

init-method="init"destroy-method="close">

<propertyname="forceShutdown"value="false"/>

</bean>

<beanid="transactionManager"class="org.springframework.transaction.jta.JtaTransactionManager">

<propertyname="userTransaction"ref="userTransaction"/>

<propertyname="transactionManager"ref="atomikosTransactionManager"/>

</bean>

<tx:annotation-driventransaction-manager="transactionManager"/>

在Tomcat配置中使用的XA的数据源和JDBC驱动，应该可以使用nonXA的相关设置，Atomikos中也支持非XA的连接，以提高运行速度。关于nonXa的数据源，可以参考一下配置：

<Resource name="jdbc/DS_MYSQL"

auth="Container"

type="com.atomikos.jdbc.nonxa.AtomikosNonXADataSourceBean"

uniqueResourceName="jdbc/DS_MYSQL"

driverClassName="com.mysql.jdbc.Driver"

maxPoolSize="200"

url="jdbc:mysql://localhost:3306/db_test?characterEncoding=UTF8"

user="root"

password="root"

factory="com.atomikos.tomcat.EnhancedTomcatAtomikosBeanFactory" />

本文中的内容参考官方文档整理：细节请查阅

https://www.atomikos.com/Documentation/Tomcat7Integration35

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