Spring AOP 動態(tài)多數(shù)據(jù)源的實例詳解

更新時間：2017年08月31日 11:38:02 作者：carl-zhao

這篇文章主要介紹了 Spring AOP 動態(tài)多數(shù)據(jù)源的實例詳解的相關(guān)資料,希望通過本文可以幫助到大家，需要的朋友可以參考下

Spring AOP 動態(tài)多數(shù)據(jù)源的實例詳解

當項目中使用到讀寫分離的時候，我們就會遇到多數(shù)據(jù)源的問題。多數(shù)據(jù)源讓人最頭痛的，不是配置多個數(shù)據(jù)源，而是如何能靈活動態(tài)的切換數(shù)據(jù)源。例如在一個spring和Mybatis的框架的項目中，我們在spring配置中往往是配置一個dataSource來連接數(shù)據(jù)庫，然后綁定給sessionFactory，在dao層代碼中再指定sessionFactory來進行數(shù)據(jù)庫操作。

正如上圖所示，每一塊都是指定綁死的，如果是多個數(shù)據(jù)源，也只能是下圖中那種方式。

可看出在Dao層代碼中寫死了兩個SessionFactory，這樣日后如果再多一個數(shù)據(jù)源，還要改代碼添加一個SessionFactory，顯然這并不符合開閉原則。

那么正確的做法應(yīng)該是：

具體代碼與配置如下:

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 動態(tài)數(shù)據(jù)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>

  <!-- 多數(shù)據(jù)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> 

  <!-- 事務(wù) -->
  <bean name="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">  
    <property name="dataSource" ref="dynamicDataSource"></property>
  </bean>
 </beans>

2、DynamicDataSource

DynamicDataSource使用Spring中的代碼結(jié)合AOP實現(xiàn)多數(shù)據(jù)源切換.

public class DynamicDataSource extends AbstractRoutingDataSource {
  public DynamicDataSource() {
  }

  protected Object determineCurrentLookupKey() {
    return DBContextHolder.getDbType();
  }

  public Logger getParentLogger() {
    return null;
  }
}

3、DBContextHolder

DynamicDataSource的輔助類，用于實際的切換多數(shù)據(jù)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

多數(shù)據(jù)源AOP切面編程實現(xiàn)。

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 動態(tài)多數(shù)據(jù)源的實例詳解，如有疑問請留言或者到本站社區(qū)交流討論，感謝閱讀，希望能幫助到大家，謝謝大家對本站的支持！

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