使用Spring解决ibatis多数据源的苦恼

iBatis多数据源的苦恼

    在仅使用ibatis时，多数据源简直就是梦魇，每多一个数据源就需要多一份sql-map-config配置文件。

    采用spring的AbstractRoutingDataSource就可以简单的解决这个问题。

    AbstractRoutingDataSource实现了javax.sql.DataSource接口，因此可以理解为一个虚拟的动态DataSource，在需要的时候根据上下文Context动态决定使用哪个数据源。

    Spring+iBatis多数据源的配置

    下面是一个完整的配置：

< 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:tx="http://www.springframework.org/schema/tx"
xmlns:jee="http://www.springframework.org/schema/jee"
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 http://www.springframework.org/schema/aop/spring-aop-2.5.xsd
   http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd
   http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-2.5.xsd">


< !-- ========================= GENERAL DEFINITIONS ========================= -->
< jee:jndi-lookup id="ds0" jndi-name="jdbc/ds0"/>
< jee:jndi-lookup id="ds1" jndi-name="jdbc/ds1"/>
< jee:jndi-lookup id="ds2" jndi-name="jdbc/ds2"/>

< bean id="dataSource" class="com.xxx.xxx.util.DynamicDataSource">
         < property name="targetDataSources">
            < map key-type="java.lang.String">
               < entry key="0" value-ref="ds0"/>
               < entry key="1" value-ref="ds1"/>
               < entry key="2" value-ref="ds2"/>
            < /map>
         < /property>
         < property name="defaultTargetDataSource" ref="1"/>
< /bean>
        < !-- SqlMap setup for iBATIS Database Layer -->
< bean id="sqlMapClient" class="org.springframework.orm.ibatis.SqlMapClientFactoryBean">
< property name="dataSource" ref="dataSource"/>
< property name="configLocation" value="classpath:com/xxx/xxx/dao/sqlmap/sql-map-config.xml"/>
< /bean>
        < bean id="testDAO" class="com.xxx.xxx.dao.impl.TestDAO">
< property name="sqlMapClient" ref="sqlMapClient"/>
< /bean>
        < bean id="testService" class="com.xxx.xxx.service.impl.TestService">
< property name="testDAO" ref="testDAO"/>
< /bean>
< /beans>



    其核心是DynamicDataSource，代码如下

package com.xxx.xxx.util;

import org.apache.log4j.Logger;
import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;

public class DynamicDataSource extends AbstractRoutingDataSource {

static Logger log = Logger.getLogger("DynamicDataSource");
@Override
protected Object determineCurrentLookupKey() {
// TODO Auto-generated method stub
return DbContextHolder.getDbType();
}

}



    上下文DbContextHolder为一线程安全的ThreadLocal，如下

package com.xxx.xxx.util;

public class DbContextHolder {
private static final ThreadLocal contextHolder = new ThreadLocal();

public static void setDbType(String dbType) {
contextHolder.set(dbType);
}

public static String getDbType() {
return (String) contextHolder.get();
}

public static void clearDbType() {
contextHolder.remove();
}
}

    sql-map-config.xml如下

< ?xml version="1.0" encoding="UTF-8" standalone="no"?>
< !DOCTYPE sqlMapConfig PUBLIC "-//iBATIS.com//DTD SQL Map Config 2.0//EN"
        "http://www.ibatis.com/dtd/sql-map-config-2.dtd">

< sqlMapConfig>

    < sqlMap resource="com/xxx/xxx/dao/sqlmap/Object.xml"/>

< /sqlMapConfig>

    这样在调用service之前只需要设置一下上下文即可调用相应的数据源，如下：

DbContextHolder.setDbType("2");
//execute services
//.........


    dao如下

package com.xxx.xxx.dao.impl;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.log4j.Logger;
import org.springframework.orm.ibatis.support.SqlMapClientDaoSupport;

import com.xxx.xxx.vo.TestObj;

public class TestDAO extends SqlMapClientDaoSupport implements ITestDAO {

    static Logger log = Logger.getLogger(TestDAO.class);

    public TestObj getTestObj(String objID) throws Exception {
        return (TestObj) getSqlMapClientTemplate().queryForObject("getTestObj", objID);
    }
}
    以上就介绍了Spring+iBatis多数据源的配置方案。