Spring AOP 动态多数据源的实例详解


             Spring AOP 动态多数据源的实例详解

当项目中使用到读写分离的时候，我们就会遇到多数据源的问题。多数据源让人最头痛的，不是配置多个数据源，而是如何能灵活动态的切换数据源。例如在一个spring和Mybatis的框架的项目中，我们在spring配置中往往是配置一个dataSource来连接数据库，然后绑定给sessionFactory，在dao层代码中再指定sessionFactory来进行数据库操作。 



 

正如上图所示，每一块都是指定绑死的，如果是多个数据源，也只能是下图中那种方式。 





可看出在Dao层代码中写死了两个SessionFactory，这样日后如果再多一个数据源，还要改代码添加一个SessionFactory，显然这并不符合开闭原则。

那么正确的做法应该是： 





具体代码与配置如下:

1、applicationContext-mgr.xml





<?xml version="1.0" encoding="utf-8" ?>

<beans xmlns="http://www.springframework.org/schema/beans"

  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 

  xmlns:aop="http://www.springframework.org/schema/aop"

  xmlns:context="http://www.springframework.org/schema/context" 

  xmlns:tx="http://www.springframework.org/schema/tx"

  xmlns:p="http://www.springframework.org/schema/p"

  xsi:schemaLocation="http://www.springframework.org/schema/beans 

    http://www.springframework.org/schema/beans/spring-beans-2.5.xsd

http://www.springframework.org/schema/aop/spring-aop-2.5.xsd

    http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd

    http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd">

  <!-- use annotation -->

  <context:annotation-config />

    <context:component-scan base-package="com.carl.o2o.**.mgr">

  </context:component-scan>



  <!-- master -->

  <bean id="master" class="com.mchange.v2.c3p0.ComboPooledDataSource">

    <property name="driverClass" value="${driverClassName_master}"/>

    <property name="user" value="${username_master}"/>

    <property name="password" value="${password_master}"/>

    <property name="jdbcUrl" value="${url_master}?Unicode=true&amp;characterEncoding=UTF-8&amp;allowMultiQueries=true"/>



    <property name="maxPoolSize" value="150"/> 

    <property name="minPoolSize" value="10"/> 

    <property name="initialPoolSize" value="20"/> 

    <property name="maxIdleTime" value="3600"/> 

    <property name="acquireIncrement" value="10"/> 

    <property name="idleConnectionTestPeriod" value="1800"/>  

  </bean>



  <!-- slave -->

  <bean id="slave" class="com.mchange.v2.c3p0.ComboPooledDataSource">

    <property name="driverClass" value="${driverClassName_slave}"/>

    <property name="user" value="${username_slave}"/>

    <property name="password" value="${password_slave}"/>

    <property name="jdbcUrl" value="${url_slave}?Unicode=true&amp;characterEncoding=UTF-8"/>



    <property name="maxPoolSize" value="150"/> 

    <property name="minPoolSize" value="10"/> 

    <property name="initialPoolSize" value="20"/> 

    <property name="maxIdleTime" value="3600"/> 

    <property name="acquireIncrement" value="10"/> 

    <property name="idleConnectionTestPeriod" value="1800"/>  

  </bean>



  <!-- spring 动态数据源 -->

  <bean id="dynamicDataSource" class="com.carl.dbUtil.DynamicDataSource">

    <property name="targetDataSources"> 

      <map key-type="java.lang.String"> 

        <entry key="slave" value-ref="slave" /> 

      </map> 

    </property> 

    <property name="defaultTargetDataSource" ref="master" />   

  </bean> 



  <!-- mybatis mapper config -->

  <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">

    <property name="dataSource" ref="dynamicDataSource"/>

    <property name="configLocation" value="classpath:o2o_mybatis_config.xml"/>

    <property name="mapperLocations" >

      <list>

        <value>classpath:sqlMap/*.xml</value>

        <value>classpath*:/com/carl/o2o/**/*.xml</value>

      </list>

    </property>

  </bean>



  <bean id="sqlSession" class="org.mybatis.spring.SqlSessionTemplate">

    <constructor-arg index="0" ref="sqlSessionFactory"></constructor-arg>

  </bean>



  <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">

    <property name="basePackage" value="com.carl.o2o.**.mgr.dao" />

  </bean>



  <!-- 多数据源 aop -->

  <bean id="DataSourceAspect" class="com.carl.dbUtil.DataSourceAspect" />

  <aop:config> 

    <aop:advisor pointcut="execution(* com.carl.o2o.mgr.*.*(..))" advice-ref="DataSourceAspect" />

  </aop:config> 



  <!-- 事务 -->

  <bean name="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">  

    <property name="dataSource" ref="dynamicDataSource"></property>

  </bean>

 </beans>







2、DynamicDataSource

DynamicDataSource使用Spring中的代码结合AOP实现多数据源切换.





public class DynamicDataSource extends AbstractRoutingDataSource {

  public DynamicDataSource() {

  }



  protected Object determineCurrentLookupKey() {

    return DBContextHolder.getDbType();

  }



  public Logger getParentLogger() {

    return null;

  }

}







3、DBContextHolder

DynamicDataSource的辅助类，用于实际的切换多数据源。





public class DBContextHolder {

  private static ThreadLocal<String> contextHolder = new ThreadLocal();

  public static String MASTER = "master";

  public static String SLAVE = "slave";



  public DBContextHolder() {

  }



  public static String getDbType() {

    String db = (String)contextHolder.get();

    if(db == null) {

      db = MASTER;

    }



    return db;

  }



  public static void setDbType(String str) {

    contextHolder.set(str);

  }



  public static void setMaster() {

    contextHolder.set(MASTER);

  }



  public static void setSlave() {

    contextHolder.set(SLAVE);

  }



  public static void clearDBType() {

    contextHolder.remove();

  }

}







4、DataSourceAspect

多数据源AOP切面编程实现。





public class DataSourceAspect implements MethodBeforeAdvice, AfterReturningAdvice, ThrowsAdvice {

  private static final Logger log = LogManager.getLogger(DataSourceAspect.class);



  public DataSourceAspect() {

  }



  public void before(Method m, Object[] args, Object target) throws Throwable {

    try {

      if(m != null) {

        if((m.getName().startsWith("list") || m.getName().startsWith("select") || m.getName().startsWith("get") 

        || m.getName().startsWith("count")) && !m.getName().contains("FromMaster")) {

          DBContextHolder.setDbType("slave");

        } else {

          DBContextHolder.setDbType("master");

        }

      }

    } catch (Exception var5) {

      log.error("data source aspect error.", var5);

    }



  }



  public void after(JoinPoint point) {

    log.info("clear db type after method.current id {}", new Object[]{Long.valueOf(Thread.currentThread().getId())});

    DBContextHolder.clearDBType();

  }



  public void afterReturning(Object returnValue, Method method, Object[] args, Object target) throws Throwable {

  }



  public void afterThrowing(Method method, Object[] args, Object target, Exception ex) throws Throwable {

    log.info("current db type {} when exception", new Object[]{DBContextHolder.getDbType()});

    DBContextHolder.setDbType("master");

  }

}







以上就是 Spring AOP 动态多数据源的实例详解，如有疑问请留言或者到本站社区交流讨论，感谢阅读，希望能帮助到大家，谢谢大家对本站的支持！