Spring+iBatis多数据源的动态配置方案

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。

下面是一个完整的配置：

Xml代码

<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

Java代码

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

Java代码

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代码

<?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：

Java代码

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

dao如下

Java代码

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);
}
}