本文的几个关键词，分布式数据源，数据源的动态寻找，分布式事务JTA实现。
???? 对于一些较大规模的应用，单个数据源是无法支撑起庞大的用户量，需要引入多数据源，水平层面进行分库分表，降低单个DB的负载。接下来，我们程序里里面需 要管理不同数据源之前的程序调用，保证功能是WORK的。另外，跨库就意味着之前单DB的事务就失效了，所以J2EE提出了JTA，分布式的事务管理，往 简单了说，就是2步提交（two phase）,比单步提交更苛刻。实际上他有两个容器来管理，一个是资源管理器，一个是事务管理。小伙伴们可以发现，这是一个环环相扣的过程。想解决一个 问题，你就得解决这几个相关的问题。以下代码，我也是参考了前辈们的思想，进行了改造。
??? 第一步：XA数据源定义
???? 选定义一个抽象的父类源，这样子类可以直接继承
??
?1??<!--?两个数据源的功用配置，方便下面直接引用?-->
?2??????<bean?id="abstractXADataSource"?class="com.atomikos.jdbc.AtomikosDataSourceBean"?init-method="init"
?3??????????????destroy-method="close"?abstract="true">
?4?????????<property?name="xaDataSourceClassName"?value="com.mysql.jdbc.jdbc2.optional.MysqlXADataSource"/>
?5?????????<property?name="poolSize"?value="10"?/>
?6?????????<property?name="minPoolSize"?value="10"/>
?7?????????<property?name="maxPoolSize"?value="30"/>
?8?????????<property?name="borrowConnectionTimeout"?value="60"/>
?9?????????<property?name="reapTimeout"?value="20"/>
10?????????<!--?最大空闲时间?-->
11?????????<property?name="maxIdleTime"?value="60"/>
12?????????<property?name="maintenanceInterval"?value="60"?/>
13?????????<property?name="loginTimeout"?value="60"/>
14?????????<property?name="logWriter"?value="60"/>
15?????????<property?name="testQuery">
16?????????????<value>select?1</value>
17?????????</property>
18?????????
19?????</bean>
20?
?? A源
?????
?1?<!--?配置第一个数据源?-->
?2?????<bean?id="dataSource_a"?parent="abstractXADataSource">
?3?????<!--?value只要两个数据源不同就行，随便取名?-->
?4?????????<property?name="uniqueResourceName"?value="mysql/sitestone"?/>
?5?????????<property?name="xaDataSourceClassName"
?6?????????????value="com.mysql.jdbc.jdbc2.optional.MysqlXADataSource"?/>
?7?????????<property?name="xaProperties">
?8?????????????<props>
?9?????????????????<prop?key="URL">${jdbc.url.spider}</prop>
10?????????????????<prop?key="user">${jdbc.username}</prop>
11?????????????????<prop?key="password">${jdbc.password}</prop>
12?????????????</props>
13?????????</property>
14?????</bean>
???
B?? 源
???
?1?<!--?配置第二个数据源-->
?2?????<bean?id="dataSource_b"?parent="abstractXADataSource">
?3?<!--?value只要两个数据源不同就行，随便取名?-->
?4?????????<property?name="uniqueResourceName"?value="mysql/sitesttwo"?/>
?5?????????<property?name="xaDataSourceClassName"
?6?????????????value="com.mysql.jdbc.jdbc2.optional.MysqlXADataSource"?/>
?7?????????<property?name="xaProperties">
?8?????????????<props>
?9????????????????<prop?key="URL">${jdbc_tb.url.spider}</prop>
10?????????????????<prop?key="user">${jdbc_tb.username}</prop>
11?????????????????<prop?key="password">${jdbc_tb.password}</prop>
12?????????????</props>
13?????????</property>
14?????</bean>
基于SPRING的AbstractRoutingDataSource动态数据路由定义
1???<bean?name="dynamicDatasource"?class="com.***.spring.datasource.CustomerDatasource">
2?????????<property?name="targetDataSources">
3?????????????<map>
4?????????????????<entry?key="ds_1"?value-ref="dataSource_a"/>
5?????????????????<entry?key="ds_2"?value-ref="dataSource_b"/>
6?????????????</map>
7?????????</property>
8?????????<property?name="defaultTargetDataSource"?ref="dataSource_a"????/>
9?????</bean>
我这里是使用MYBATIS来进行ORM映射，配置如下
?1??<bean?id="sqlSessionFactorya"?class="org.mybatis.spring.SqlSessionFactoryBean">
?2?????????<property?name="dataSource"?ref="dataSource_a"/>
?3??????????<property?name="typeAliasesPackage"?value="com.****.spring.dschange.bean"?/>
?4??????????<!--?mapper和resultmap配置路径?-->?
?5?????????<property?name="mapperLocations">
?6?????????????<list>
?7?????????????????<!--?表示在com.**目录下的任意包下的resultmap包目录中，以-resultmap.xml或-mapper.xml结尾所有文件?-->?
?8?????????????????<value>classpath:com/***/spring/dschange/mapper/ShopMapper.xml</value>
?9?????????????</list>
10?????????</property>
11?????</bean>
12?????<bean?id="sqlSessionFactoryb"?class="org.mybatis.spring.SqlSessionFactoryBean">
13?????????<property?name="dataSource"?ref="dataSource_b"/>
14??????????<property?name="typeAliasesPackage"?value="com.****.spring.dschange.bean"?/>
15???????????<!--?mapper和resultmap配置路径?-->?
16?????????<property?name="mapperLocations">
17?????????????<list>
18?????????????????<!--?表示在com.***目录下的任意包下的resultmap包目录中，以-resultmap.xml或-mapper.xml结尾所有文件?-->?
19?????????????????<value>classpath:com/***/spring/dschange/mapper/ShopMapper.xml</value>
20?????????????</list>
21?????????</property>
22?????</bean>
接下来，一个比较关键的地方是对MYBATIS的CustomSqlSessionTemplate的重写，主要是引入动态数据源sqlSessionFactory。针对不同的数据库，调用其对应的会话工厂，这对JTA是否启用，比较重要。
?1?
?@Override
?2?
????public?SqlSessionFactory?getSqlSessionFactory()?{
?3?
?
?4?
????????SqlSessionFactory?targetSqlSessionFactory?=?targetSqlSessionFactorys.get(DataSourceKeyHolder.getDataSourceKey());
?5?
????????if?(targetSqlSessionFactory?!=?
null)?{
?6?
????????????return?targetSqlSessionFactory;
?7?
????????}?else?
if?(defaultTargetSqlSessionFactory?!=?
null)?{
?8?
????????????return?defaultTargetSqlSessionFactory;
?9?
????????}?else?{
10?
????????????Assert.notNull(targetSqlSessionFactorys,?"Property?‘targetSqlSessionFactorys‘?or?‘defaultTargetSqlSessionFactory‘?are?required");
11?
????????????Assert.notNull(defaultTargetSqlSessionFactory,?"Property?‘defaultTargetSqlSessionFactory‘?or?‘targetSqlSessionFactorys‘?are?required");
12?
????????}
13?
????????return?
this.sqlSessionFactory;
14?
????}
XML配置
?1??<!--?配置自定义的SqlSessionTemplate模板，注入相关配置?-->
?2?????<bean?id="sqlSessionTemplate"?class="com.amos.spring.mybatis.CustomSqlSessionTemplate"?scope="prototype">
?3?????????<constructor-arg?ref="sqlSessionFactorya"?/>
?4?????????<property?name="targetSqlSessionFactorys">
?5?????????????<map>?????
?6?????????????????<entry?value-ref="sqlSessionFactorya"?key="ds_1"/>
?7?????????????????<entry?value-ref="sqlSessionFactoryb"?key="ds_2"/>
?8?????????????</map>?
?9?????????</property>
10?????</bean>
扫描配置
1??
<bean?id="mapperScannerConfigurer"?class="org.mybatis.spring.mapper.MapperScannerConfigurer">
?1?????<!--?jta?-->
?2?????<bean?id="atomikosTransactionManager"?class="com.atomikos.icatch.jta.UserTransactionManager"
?3?????????init-method="init"?destroy-method="close">
?4?????????<property?name="forceShutdown">
?5?????????????<value>true</value>
?6?????????</property>
?7?????</bean>
?8??
?9?????<bean?id="atomikosUserTransaction"?class="com.atomikos.icatch.jta.UserTransactionImp">
10?????????<property?name="transactionTimeout"?value="300"?/>
11?????</bean>
12??
13?????<bean?id="springTransactionManager"
14?????????class="org.springframework.transaction.jta.JtaTransactionManager">
15?????????<property?name="transactionManager">
16?????????????<ref?bean="atomikosTransactionManager"?/>
17?????????</property>
18?????????<property?name="userTransaction">
19?????????????<ref?bean="atomikosUserTransaction"?/>
20?????????</property>
21?????</bean>
22??<tx:annotation-driven?transaction-manager="springTransactionManager"?proxy-target-class="true"?/>
2?
????????<property?name="basePackage"?value="com.****.spring.dschange.mapper"?
/>
3?
????????<property?name="sqlSessionTemplateBeanName"?value="sqlSessionTemplate"/>
4?
????????<property?name="markerInterface"?value="com.*****.spring.dschange.mapper.SqlMapper"/>
5?
????</bean>
最后就是JTA的实现配置
?1?????<!--?jta?-->
?2?????<bean?id="atomikosTransactionManager"?class="com.atomikos.icatch.jta.UserTransactionManager"
?3?????????init-method="init"?destroy-method="close">
?4?????????<property?name="forceShutdown">
?5?????????????<value>true</value>
?6?????????</property>
?7?????</bean>
?8??
?9?????<bean?id="atomikosUserTransaction"?class="com.atomikos.icatch.jta.UserTransactionImp">
10?????????<property?name="transactionTimeout"?value="300"?/>
11?????</bean>
12??
13?????<bean?id="springTransactionManager"
14?????????class="org.springframework.transaction.jta.JtaTransactionManager">
15?????????<property?name="transactionManager">
16?????????????<ref?bean="atomikosTransactionManager"?/>
17?????????</property>
18?????????<property?name="userTransaction">
19?????????????<ref?bean="atomikosUserTransaction"?/>
20?????????</property>
21?????</bean>
22??<tx:annotation-driven?transaction-manager="springTransactionManager"?proxy-target-class="true"?/>
以上,XML配置相关的东西已经完成。
具体的代码，请点击GITHUB查看https://github.com/igool/spring-jta-mybatis
基于spring,Atomikos,mybatis的分布式动态数据源JTA实现
原文：http://zuxiong.iteye.com/blog/2246517
