Spring 实现数据库读写分离的示例

public interface DataSource extends CommonDataSource,Wrapper {

 /**
  * <p>Attempts to establish a connection with the data source that
  * this <code>DataSource</code> object represents.
  *
  * @return a connection to the data source
  * @exception SQLException if a database access error occurs
  */
 Connection getConnection() throws SQLException;

 /**
  * <p>Attempts to establish a connection with the data source that
  * this <code>DataSource</code> object represents.
  *
  * @param username the database user on whose behalf the connection is
  * being made
  * @param password the user's password
  * @return a connection to the data source
  * @exception SQLException if a database access error occurs
  * @since 1.4
  */
 Connection getConnection(String username, String password)
  throws SQLException;

}

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

  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;
  }

Object lookupKey = determineCurrentLookupKey();
DataSource dataSource = this.resolvedDataSources.get(lookupKey);

　　private Map<Object, DataSource> resolvedDataSources;

　　protected abstract Object determineCurrentLookupKey()

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface DataSource {
  String value();
}

public class DynamicDataSource extends AbstractRoutingDataSource {

  @Override
  protected Object determineCurrentLookupKey() {
    // TODO Auto-generated method stub
    return DynamicDataSourceHolder.getDataSouce();
  }

}


public class DynamicDataSourceHolder {
  public static final ThreadLocal<String> holder = new ThreadLocal<String>();

  public static void putDataSource(String name) {
    holder.set(name);
  }

  public static String getDataSouce() {
    return holder.get();
  }
}

public class DataSourceAspect {

  public void before(JoinPoint point)
  {
    Object target = point.getTarget();
    String method = point.getSignature().getName();

    Class<?>[] classz = target.getClass().getInterfaces();

    Class<?>[] parameterTypes = ((MethodSignature) point.getSignature())
        .getMethod().getParameterTypes();
    try {
      Method m = classz[0].getMethod(method, parameterTypes);
      if (m != null && m.isAnnotationPresent(DataSource.class)) {
        DataSource data = m
            .getAnnotation(DataSource.class);
        DynamicDataSourceHolder.putDataSource(data.value());
        System.out.println(data.value());
      }
      
    } catch (Exception e) {
      // TODO: handle exception
    }
  }
}

<bean id="masterdataSource"
    class="org.springframework.jdbc.datasource.DriverManagerDataSource">
    <property name="driverClassName" value="com.mysql.jdbc.Driver" />
    <property name="url" value="jdbc:mysql://127.0.0.1:3306/shop" />
    <property name="username" value="root" />
    <property name="password" value="yangyanping0615" />
  </bean>

  <bean id="slavedataSource"
    class="org.springframework.jdbc.datasource.DriverManagerDataSource">
    <property name="driverClassName" value="com.mysql.jdbc.Driver" />
    <property name="url" value="jdbc:mysql://127.0.0.1:3306/test" />
    <property name="username" value="root" />
    <property name="password" value="yangyanping0615" />
  </bean>
  
    <beans:bean id="dataSource" class="com.air.shop.common.db.DynamicDataSource">
    <property name="targetDataSources"> 
       <map key-type="java.lang.String"> 
         <!-- write -->
         <entry key="master" value-ref="masterdataSource"/> 
         <!-- read -->
         <entry key="slave" value-ref="slavedataSource"/> 
       </map> 
       
    </property> 
    <property name="defaultTargetDataSource" ref="masterdataSource"/> 
  </beans:bean>

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


  <!-- 配置SqlSessionFactoryBean -->
  <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
    <property name="dataSource" ref="dataSource" />
    <property name="configLocation" value="classpath:config/mybatis-config.xml" />
  </bean>

<!-- 配置数据库注解aop -->
  <aop:aspectj-autoproxy></aop:aspectj-autoproxy>
  <beans:bean id="manyDataSourceAspect" class="com.air.shop.proxy.DataSourceAspect" />
  <aop:config>
    <aop:aspect id="c" ref="manyDataSourceAspect">
      <aop:pointcut id="tx" expression="execution(* com.air.shop.mapper.*.*(..))"/>
      <aop:before pointcut-ref="tx" method="before"/>
    </aop:aspect>
  </aop:config>
  <!-- 配置数据库注解aop -->

public interface UserMapper {
  @DataSource("master")
  public void add(User user);

  @DataSource("master")
  public void update(User user);

  @DataSource("master")
  public void delete(int id);

  @DataSource("slave")
  public User loadbyid(int id);

  @DataSource("master")
  public User loadbyname(String name);
  
  @DataSource("slave")
  public List<User> list();
}