使用spring配置多个数据源

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1.数据源定义

这里以2个c3p0数据库连接池的数据源作为实例。在spring框架下需要加入c3p0的依赖。这里以数据同步为例：

（1）数据库来源的连接池数据源配置

<bean id="dataSourceFrom" class="com.mchange.v2.c3p0.ComboPooledDataSource">      <property name="driverClass" value="${jdbc.driver}" />      <property name="jdbcUrl" value="${jdbc.from.url}" />      <property name="user" value="${jdbc.from.username}" />      <property name="password" value="${jdbc.from.password}" />      <property name="autoCommitOnClose" value="true" />      <property name="checkoutTimeout" value="${cpool.checkoutTimeout}" />      <property name="initialPoolSize" value="${cpool.minPoolSize}" />      <property name="minPoolSize" value="${cpool.minPoolSize}" />      <property name="maxPoolSize" value="${cpool.maxPoolSize}" />      <property name="maxIdleTime" value="${cpool.maxIdleTime}" />      <property name="acquireIncrement" value="${cpool.acquireIncrement}" />      <property name="maxIdleTimeExcessConnections" value="${cpool.maxIdleTimeExcessConnections}" />  </bean>

（2）数据插入库的连接池数据源配置

<bean id="dataSourceTo" class="com.mchange.v2.c3p0.ComboPooledDataSource">      <property name="driverClass" value="${jdbc.driver}" />      <property name="jdbcUrl" value="${jdbc.from.url}" />      <property name="user" value="${jdbc.from.username}" />      <property name="password" value="${jdbc.from.password}" />      <property name="autoCommitOnClose" value="true" />      <property name="checkoutTimeout" value="${cpool.checkoutTimeout}" />      <property name="initialPoolSize" value="${cpool.minPoolSize}" />      <property name="minPoolSize" value="${cpool.minPoolSize}" />      <property name="maxPoolSize" value="${cpool.maxPoolSize}" />      <property name="maxIdleTime" value="${cpool.maxIdleTime}" />      <property name="acquireIncrement" value="${cpool.acquireIncrement}" />      <property name="maxIdleTimeExcessConnections" value="${cpool.maxIdleTimeExcessConnections}" />  </bean>

2.扩展Spring的AbstractRoutingDataSource

AbstractRoutingDataSource中的抽象方法determineCurrentLookupKey是实现数据源的route的核心，这里对该方法进行重写

public class DynamicDataSource extends AbstractRoutingDataSource{        @Override      protected Object determineCurrentLookupKey() {          return DBContextHolder.getDBType();      }  }

其中DBContextHolder是一个线程安全的ThreadLocal，具体代码如下：

public class DBContextHolder{      public static final String DATA_SOURCE_FROM = "dataSourceFrom";      public static final String DATA_SOURCE_TO = "dataSourceTo";            private static final ThreadLocal contextHolder = new ThreadLocal();            public static void setDBType(String dbType) {          contextHolder.set(dbType);      }            public static String getDBType() {          return contextHolder.get();      }            public static void clearDBType() {          contextHolder.remove();      }  }

3.配置动态数据源

将DynamicDataSource加入到spring的配置文件中，同时配置DynamicDataSource的targetDataSource（也就是多个数据源）属性的Map映射

<bean id="dynamicDataSource" class="datasource.DynamicDataSource" >            <property name="targetDataSources">          <map>              <entry value-ref="dataSourceFrom" key="dataSourceFrom"></entry>              <entry value-ref="dataSourceTo" key="dataSourceTo"></entry>          </map>      </property>      <property name="defaultTargetDataSource" ref="dataSourceFrom" />  </bean>

4.使用动态数据源

说明：例子中的DynamicDataSource继承自AbstractRoutingDataSource，而AbstractRoutingDataSource有继承自AbstractDataSource，AbstractDataSource实现了统一的DataSource接口，所以DynamicDataSource同样可以当做一个DataSource来使用

这里使用ibatis作为持久层框架

   <bean id="sqlMapClient" class="org.springframework.orm.ibatis.SqlMapClientFactoryBean">          <property name="dataSource" ref="dynamicDataSource<span style="font-family: Arial, Helvetica, sans-serif;">"</span><span style="font-family: Arial, Helvetica, sans-serif;">/>  </span>        <property name="configLocation" value="classpath:com/xxx/xxx/dao/sqlmap/sql-map-config.xml"/>      </bean>          <bean id="userDAO" class="com.xxx.xxx.dao.impl.UserDAO">          <property name="sqlMapClient" ref="sqlMapClient"/>      </bean>

5.事务管理

使用动态数据源的时候，事务管理和单数据源没有差别

    <bean id="txManager"          class="org.springframework.jdbc.datasource.DataSourceTransactionManager">          <property name="dataSource" ref="dynamicDataSource" <span style="font-family: Arial, Helvetica, sans-serif;">/>  </span>    </bean>        <tx:advice id="txAdvice" transaction-manager="txManager">          <tx:attributes>              <tx:method name="save*" propagation="REQUIRED" />              <tx:method name="delete*" propagation="REQUIRED" />              <tx:method name="update*" propagation="REQUIRED" />              <tx:method name="select*" propagation="REQUIRED" />              <tx:method name="*" propagation="REQUIRES_NEW"                  rollback-for="Exception" />          </tx:attributes>      </tx:advice>        <aop:config proxy-target-class="false">          <aop:advisor pointcut="execution(* com.mycompany.app.service.impl.*.*(..))"              advice-ref="txAdvice" />      </aop:config>        <bean id="sqlMapClient" class="org.springframework.orm.ibatis.SqlMapClientFactoryBean">          <property name="configLocation">  <!-- name 为configLocation或s 不可为其他 -->              <value>sqlMap.xml</value> <!-- 不区分大小写，路径前可加'/' -->          </property>          <!-- dataSource不是必需 -->          <property name="dataSource">              <ref local="dynamicDataSource"<span style="font-family: Arial, Helvetica, sans-serif;"> />  </span>        </property>      </bean>

6.使用

（1）手动控制

ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");  BaseDAO dao = (BaseDAO) context.getBean("sqlBaseDAO", BaseDAOImpl.class);    try {      DBContextHolder.setCustomerType(DBContextHolder.DATA_SOURCE_FROM);      System.err.println(dao.select("select count(*) sum from TEST t ").get(0).get("SUM"));      DBContextHolder.setCustomerType(DBContextHolder.DATA_SOURCE_TO);      System.err.println(dao.select("select count(*) sum from TEST t ").get(0).get("SUM"));        } catch (Exception e) {      e.printStackTrace();  }

（2）使用AOP控制

@Aspect  public class DynamicDataSourceAspect {      @Pointcut("execution (public service.impl..*.*(..))")      public void serviceExecution(){}            @Before("serviceExecution()")      public void setDynamicDataSource(JoinPoint jp) {          for(Object o : jp.getArgs()) {              //处理具体的逻辑 ，根据具体的境况CustomerContextHolder.setCustomerType()选取DataSource          }      }  }

7.注意

必须在开启事务之前就切换好数据源，因为事务是和数据源绑定的。

如事务控制设置在service层，那么切换数据源就必须在上一层，也就是Controller层

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