Spring 配置多個數據源，並實現動態切換

1.配置兩個不同的數據源，如下

<!-- 數據源配置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>
<!-- 監控數據庫 -->
<property name="proxyFilters">
<list>
<ref bean="log-filter" />
</list>
</property>

</bean>

<!-- 數據源配置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>
<!-- 監控數據庫 -->
<property name="proxyFilters">
<list>
<ref bean="log-filter" />
</list>
</property>

</bean>

2.定義一個類繼承AbstractRoutingDataSource實現determineCurrentLookupKey方法，該方法可以實現數據庫的動態切換，如下：

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

3.定義一個可以設置當前線程的變量的工具類，用於設置對應的數據源名稱：

public class DataSourceContextHolder {
private static final ThreadLocal<String> contextHolder = new ThreadLocal<String>();
/**
* @Description: 設置數據源類型
* @param dataSourceType 數據庫類型
* @return void
* @throws
*/
public static void setDataSourceType(String dataSourceType) {
contextHolder.set(dataSourceType);
}

/**
* @Description: 獲取數據源類型
* @param
* @return String
* @throws
*/
public static String getDataSourceType() {
return contextHolder.get();
}

/**
* @Description: 清除數據源類型
* @param
* @return void
* @throws
*/
public static void clearDataSourceType() {
contextHolder.remove();
}
}

然后在spring中配置，如下：

<!-- 編寫spring 配置文件的配置多數源映射關系 -->
<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>

這樣配置兩個數據源對應的key分別為testDataSource1和testDataSource2，默認數據庫是testDataSource。
4.完成以上步驟后，如果沒有數據庫的事務管理，已經可以實現數據庫的動態切換了。但是如果涉及到數據庫的事務管理，需要在數據庫事務開啟切換數據庫，

否則數據庫的切換只能在下次數據庫操作時才生效。可以定義一個aop處理類在數據庫事務開啟之前切換數據庫，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.設置數據庫事務切面和切換數據庫切面執行的順序，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屬性設置執行的順序，這樣實現了帶事務管理的spring數據庫動態切換。