1.配置两个不同的数据源，如下

<!-- 数据源配置1 -->
<bean id="testDataSource1" class="com.alibaba.druid.pool.DruidDataSource" init-method="init" destroy-method="close">
<property name="driverClassName" value="${db.driver}" />
<property name="url" value="${unity.db.jdbc.url}" />
<property name="username" value="${db.login.name}"></property>
<property name="password" value="${db.login.password}" />
<property name="filters" value="${db.filters}"></property>
<property name="maxActive" value="${db.pool.maxActive}"></property>
<property name="initialSize" value="${db.pool.initialSize}"></property>
<property name="minIdle" value="${db.pool.minIdle}"></property>
<property name="maxWait" value="${db.maxWait}"></property>
<property name="timeBetweenEvictionRunsMillis" value="${db.timeBetweenEvictionRunsMillis}"></property>
<property name="minEvictableIdleTimeMillis" value="${db.minEvictableIdleTimeMillis}"></property>
<property name="validationQuery" value="${db.validationQuery}"></property>
<property name="testWhileIdle" value="${db.testWhileIdle}"></property>
<property name="testOnBorrow" value="${db.testOnBorrow}"></property>
<property name="testOnReturn" value="${db.testOnReturn}"></property>
<property name="poolPreparedStatements" value="${db.poolPreparedStatements}"></property>
<property name="maxOpenPreparedStatements" value="${db.maxOpenPreparedStatements}"></property>
<!-- 监控数据库 -->
<property name="proxyFilters">
<list>
<ref bean="log-filter" />
</list>
</property>

</bean>

<!-- 数据源配置2 -->
<bean id="testDataSource2" class="com.alibaba.druid.pool.DruidDataSource" init-method="init" destroy-method="close">
<property name="driverClassName" value="${db.driver}" />
<property name="url" value="${pub.db.jdbc.url}" />
<property name="username" value="${db.login.name}"></property>
<property name="password" value="${db.login.password}" />
<property name="filters" value="${db.filters}"></property>
<property name="maxActive" value="${db.pool.maxActive}"></property>
<property name="initialSize" value="${db.pool.initialSize}"></property>
<property name="minIdle" value="${db.pool.minIdle}"></property>
<property name="maxWait" value="${db.maxWait}"></property>
<property name="timeBetweenEvictionRunsMillis" value="${db.timeBetweenEvictionRunsMillis}"></property>
<property name="minEvictableIdleTimeMillis" value="${db.minEvictableIdleTimeMillis}"></property>
<property name="validationQuery" value="${db.validationQuery}"></property>
<property name="testWhileIdle" value="${db.testWhileIdle}"></property>
<property name="testOnBorrow" value="${db.testOnBorrow}"></property>
<property name="testOnReturn" value="${db.testOnReturn}"></property>
<property name="poolPreparedStatements" value="${db.poolPreparedStatements}"></property>
<property name="maxOpenPreparedStatements" value="${db.maxOpenPreparedStatements}"></property>
<!-- 监控数据库 -->
<property name="proxyFilters">
<list>
<ref bean="log-filter" />
</list>
</property>

</bean>

2.定义一个类继承AbstractRoutingDataSource实现determineCurrentLookupKey方法，该方法可以实现数据库的动态切换，如下：

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

3.定义一个可以设置当前线程的变量的工具类，用于设置对应的数据源名称：

public class DataSourceContextHolder {
private static final ThreadLocal<String> contextHolder = new ThreadLocal<String>();
/**
* @Description: 设置数据源类型
* @param dataSourceType 数据库类型
* @return void
* @throws
*/
public static void setDataSourceType(String dataSourceType) {
contextHolder.set(dataSourceType);
}

/**
* @Description: 获取数据源类型
* @param
* @return String
* @throws
*/
public static String getDataSourceType() {
return contextHolder.get();
}

/**
* @Description: 清除数据源类型
* @param
* @return void
* @throws
*/
public static void clearDataSourceType() {
contextHolder.remove();
}
}

然后在spring中配置，如下：

<!-- 编写spring 配置文件的配置多数源映射关系 -->
<bean class="com.sino.access.database.DynamicDataSource" id="dataSource">
<property name="targetDataSources">
<map key-type="java.lang.String">
<entry value-ref="testDataSource1" key="<span style="font-family: Arial, Helvetica, sans-serif;">testDataSource1</span><span style="font-family: Arial, Helvetica, sans-serif;">"></entry></span>
<entry value-ref="testDataSource2" key="testDataSource2"></entry>
</map>
</property>
<property name="defaultTargetDataSource" ref="testDataSource1">
</property>
</bean>

这样配置两个数据源对应的key分别为testDataSource1和testDataSource2，默认数据库是testDataSource。
4.完成以上步骤后，如果没有数据库的事务管理，已经可以实现数据库的动态切换了。但是如果涉及到数据库的事务管理，需要在数据库事务开启切换数据库，

否则数据库的切换只能在下次数据库操作时才生效。可以定义一个aop处理类在数据库事务开启之前切换数据库，如下：

public class DataSourceAspect implements MethodBeforeAdvice,AfterReturningAdvice
{

@Override
public void afterReturning(Object returnValue, Method method,
Object[] args, Object target) throws Throwable {
// TODO Auto-generated method stub
DataSourceContextHolder.clearDataSourceType();
}

@Override
public void before(Method method, Object[] args, Object target)
throws Throwable {

if (method.isAnnotationPresent(DataSource.class))
{
DataSource datasource = method.getAnnotation(DataSource.class);
DataSourceContextHolder.setDataSourceType(datasource.name());
}
else
{
DataSourceContextHolder.setDataSourceType(SinoConstant.DataSourceType.unityDataSource.toString());
}

}
}

5.设置数据库事务切面和切换数据库切面执行的顺序，如下：

<aop:config>
<aop:pointcut id="transactionPointCut" expression="execution(* com.test.service.*.*(..))" />
<aop:advisor pointcut-ref="transactionPointCut"
advice-ref="txAdvice" order="2" />
<aop:advisor advice-ref="dataSourceExchange" pointcut-ref="transactionPointCut" order="1"/>
</aop:config>

利用aop的order属性设置执行的顺序，这样实现了带事务管理的spring数据库动态切换。