使用Spring的AbstractRoutingDataSource实现多数据源切换示例

public abstract class AbstractRoutingDataSource extends AbstractDataSource implements InitializingBean {
  /* 只列出部分代码 */
  private Map<Object, Object> targetDataSources;

  private Object defaultTargetDataSource;

  private boolean lenientFallback = true;

  private DataSourceLookup dataSourceLookup = new JndiDataSourceLookup();

  private Map<Object, DataSource> resolvedDataSources;

  private DataSource resolvedDefaultDataSource;

  @Override
  public Connection getConnection() throws SQLException {
    return determineTargetDataSource().getConnection();
  }

  @Override
  public Connection getConnection(String username, String password) throws SQLException {
    return determineTargetDataSource().getConnection(username, password);
  }

  protected DataSource determineTargetDataSource() {
    Assert.notNull(this.resolvedDataSources, "DataSource router not initialized");
    Object lookupKey = determineCurrentLookupKey();
    DataSource dataSource = this.resolvedDataSources.get(lookupKey);
    if (dataSource == null && (this.lenientFallback || lookupKey == null)) {
      dataSource = this.resolvedDefaultDataSource;
    }
    if (dataSource == null) {
      throw new IllegalStateException("Cannot determine target DataSource for lookup key [" + lookupKey + "]");
    }
    return dataSource;
  }

  protected abstract Object determineCurrentLookupKey();
}

/**
 * 获得数据源
 */
public class MultipleDataSource extends AbstractRoutingDataSource{

  @Override
  protected Object determineCurrentLookupKey() {
     return DynamicDataSourceHolder.getRouteKey();
  }
}

/**
 * 数据源操作类
 */
public class DynamicDataSourceHolder {
  private static ThreadLocal<String> routeKey = new ThreadLocal<String>();

  /**
   * 获取当前线程的数据源路由的key
   */
  public static String getRouteKey()
  {
    String key = routeKey.get();
    return key;
  }

  /**
   * 绑定当前线程数据源路由的key
   * 使用完成后必须调用removeRouteKey()方法删除
   */
  public static void setRouteKey(String key)
  {
    routeKey.set(key);
  }

  /**
   * 删除与当前线程绑定的数据源路由的key
   */
  public static void removeRouteKey()
  {
    routeKey.remove();
  }
}

<!-- 数据源 -->
<bean id="dataSource1" class="org.apache.commons.dbcp.BasicDataSource">
   <property name="driverClassName" value="net.sourceforge.jtds.jdbc.Driver">
   </property>
   <property name="url" value="jdbc:jtds:sqlserver://127.0.0.1;databaseName=test">
   </property>
   <property name="username" value="***"></property>
   <property name="password" value="***"></property>
 </bean>
 <bean id="dataSource2" class="org.apache.commons.dbcp.BasicDataSource">
   <property name="driverClassName" value="net.sourceforge.jtds.jdbc.Driver">
   </property>
   <property name="url" value="jdbc:jtds:sqlserver://127.0.0.2:1433;databaseName=test">
   </property>
   <property name="username" value="***"></property>
   <property name="password" value="***"></property>
</bean>

<!-- 配置多数据源映射 -->
<bean id="multipleDataSource" class="MultipleDataSource" >
   <property name="targetDataSources">
     <map key-type="java.lang.String">
       <entry value-ref="dataSource1" key="dataSource1"></entry>
       <entry value-ref="dataSource2" key="dataSource2"></entry>
     </map>
   </property>
   <!-- 默认数据源 -->
   <property name="defaultTargetDataSource" ref="dataSource1" >
   </property>
</bean>

DynamicDataSourceHolder.setRouteKey("dataSource2");

@DataSourceKey("dataSource1")
public interface TestEntityMapper extends MSSQLMapper<TestEntity> {
  public void insertTest(TestEntity testEntity);
}

@Target({ElementType.TYPE,ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface DataSourceKey {
  String value() default "";
}

public class MultipleDataSourceExchange {

  /** 
   * 拦截目标方法，获取由@DataSource指定的数据源标识，设置到线程存储中以便切换数据源 
   */ 
  public void beforeDaoMethod(JoinPoint point) throws Exception { 
    Class<?> target = point.getTarget().getClass(); 
    MethodSignature signature = (MethodSignature) point.getSignature(); 
    // 默认使用目标类型的注解，如果没有则使用其实现接口的注解类 
    for (Class<?> cls : target.getInterfaces()) { 
      resetDataSource(cls, signature.getMethod()); 
    } 
    resetDataSource(target, signature.getMethod()); 
  } 


  /** 
   * 提取目标对象方法注解和类注解中的数据源标识 
   */ 
  private void resetDataSource(Class<?> cls, Method method) { 
    try { 
      Class<?>[] types = method.getParameterTypes(); 
      // 默认使用类注解 
      if (cls.isAnnotationPresent(DataSourceKey.class)) { 
        DataSourceKey source = cls.getAnnotation(DataSourceKey.class); 
        DynamicDataSourceHolder.setRouteKey(source.value()); 
      } 
      // 方法注解可以覆盖类注解 
      Method m = cls.getMethod(method.getName(), types); 
      if (m != null && m.isAnnotationPresent(DataSourceKey.class)) { 
        DataSourceKey source = m.getAnnotation(DataSourceKey.class);  
        DynamicDataSourceHolder.setRouteKey(source.value()); 
      } 
    } catch (Exception e) { 
      System.out.println(cls + ":" + e.getMessage()); 
    } 
  } 
}

<bean id="multipleDataSourceExchange" class="MultipleDataSourceExchange "/>

<bean id="txManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
  <property name="dataSource" ref="multipleDataSource" />
</bean>

<tx:advice id="txAdvice" transaction-manager="txManager">
  <tx:attributes>
    <tx:method name="insert*" propagation="NESTED" rollback-for="Exception"/>
    <tx:method name="add*" propagation="NESTED" rollback-for="Exception"/>
    ...
  </tx:attributes>
</tx:advice>

<aop:config>
  <aop:pointcut id="service" expression="execution(* com.datasource..*.service.*.*(..))"/>
  <!-- 注意切换数据源操作要比持久层代码先执行 -->
  <aop:advisor advice-ref="multipleDataSourceExchange" pointcut-ref="service" order="1"/>
  <aop:advisor advice-ref="txAdvice" pointcut-ref="service" order="2"/>
</aop:config>