Spring+iBatis多数据源的动态配置方案

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摘自：http://blog.csdn.net/yczz/article/details/5893878

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 
<beansxmlns="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-lookupid="ds0"jndi-name="jdbc/ds0"/> 
    <jee:jndi-lookupid="ds1"jndi-name="jdbc/ds1"/> 
    <jee:jndi-lookupid="ds2"jndi-name="jdbc/ds2"/> 
      
    <beanid="dataSource"class="com.xxx.xxx.util.DynamicDataSource">    
           <propertyname="targetDataSources">    
              <mapkey-type="java.lang.String">    
                 <entrykey="0"value-ref="ds0"/> 
                 <entrykey="1"value-ref="ds1"/> 
                 <entrykey="2"value-ref="ds2"/>    
              </map>    
           </property>    
           <propertyname="defaultTargetDataSource"ref="1"/>    
    </bean> 
       <!-- SqlMap setup for iBATIS Database Layer --> 
    <beanid="sqlMapClient"class="org.springframework.orm.ibatis.SqlMapClientFactoryBean"> 
       <propertyname="dataSource"ref="dataSource"/> 
       <propertyname="configLocation"value="classpath:com/xxx/xxx/dao/sqlmap/sql-map-config.xml"/> 
    </bean> 
       <beanid="testDAO"class="com.xxx.xxx.dao.impl.TestDAO"> 
       <propertyname="sqlMapClient"ref="sqlMapClient"/> 
    </bean> 
       <beanid="testService"class="com.xxx.xxx.service.impl.TestService"> 
       <propertyname="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;   
  
publicclass 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;   
  
publicclass DbContextHolder {   
    privatestaticfinal ThreadLocal contextHolder = new ThreadLocal();   
  
    publicstaticvoid setDbType(String dbType) {   
        contextHolder.set(dbType);  
    }  
  
    publicstatic String getDbType() {   
       return (String) contextHolder.get();   
    }  
  
    publicstaticvoid clearDbType() {   
        contextHolder.remove();  
    }  
}  

sql-map-config.xml如下

Xml代码 
<?xmlversion="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> 
  
    <sqlMapresource="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;   
  
publicclass 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);   
    }  
}  

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