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&characterencoding=utf-8&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&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！