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。

e就可以简单的解决这个问题。

e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：





1. beansxmlns="http://www.springframework.org/schema/beans" 
2.        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
3.        xmlns:aop="http://www.springframework.org/schema/aop" 
4.        xmlns:tx="http://www.springframework.org/schema/tx" 
5.        xmlns:jee="http://www.springframework.org/schema/jee" 
6.        xsi:schemaLocation="   
7.            http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd   
8.            http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.5.xsd   
9.            http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd   
10.            http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-2.5.xsd"> 
11.  
12.  
13.     
14.    <</span>jee:jndi-lookupid="ds0"jndi-name="jdbc/ds0"/> 
15.    <</span>jee:jndi-lookupid="ds1"jndi-name="jdbc/ds1"/> 
16.    <</span>jee:jndi-lookupid="ds2"jndi-name="jdbc/ds2"/> 
17.       
18.    <</span>beanid="dataSource"class="com.xxx.xxx.util.DynamicDataSource">    
19.            <</span>propertyname="targetDataSources">    
20.               <</span>mapkey-type="java.lang.String">    
21.                  <</span>entrykey="0"value-ref="ds0"/> 
22.                  <</span>entrykey="1"value-ref="ds1"/> 
23.                  <</span>entrykey="2"value-ref="ds2"/>    
24.               </</span>map>    
25.            </</span>property>    
26.            <</span>propertyname="defaultTargetDataSource"ref="1"/>    
27.    </</span>bean> 
28.         
29.    <</span>beanid="sqlMapClient"class="org.springframework.orm.ibatis.SqlMapClientFactoryBean"> 
30.        <</span>propertyname="dataSource"ref="dataSource"/> 
31.        <</span>propertyname="configLocation"value="classpath:com/xxx/xxx/dao/sqlmap/sql-map-config.xml"/> 
32.    </</span>bean> 
33.        <</span>beanid="testDAO"class="com.xxx.xxx.dao.impl.TestDAO"> 
34.        <</span>propertyname="sqlMapClient"ref="sqlMapClient"/> 
35.    </</span>bean> 
36.        <</span>beanid="testService"class="com.xxx.xxx.service.impl.TestService"> 
37.        <</span>propertyname="testDAO"ref="testDAO"/> 
38.    </</span>bean> 
39. beans>



其核心是DynamicDataSource，代码如下


1.  packagecom.xxx.xxx.util;   
2.  
3.  importorg.apache.log4j.Logger;   
4.  importorg.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;   
5.  
6.  publicclassDynamicDataSource extendsAbstractRoutingDataSource {   
7.  
8.    staticLogger log = Logger.getLogger("DynamicDataSource");   
9.    @Override 
10.    protectedObject determineCurrentLookupKey() {   
11.        // TODO Auto-generated method stub  
12.        returnDbContextHolder.getDbType();   
13.    }   
14.  
15.


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


1.  packagecom.xxx.xxx.util;   
2.  
3.  publicclassDbContextHolder {   
4.    privatestaticfinalThreadLocal contextHolder = newThreadLocal();   
5.  
6.    publicstaticvoidsetDbType(String dbType) {   
7.        contextHolder.set(dbType);   
8.    }   
9.  
10.    publicstaticString getDbType() {   
11.        return(String) contextHolder.get();   
12.    }   
13.  
14.    publicstaticvoidclearDbType() {   
15.        contextHolder.remove();   
16.    }   
17.



sql-map-config.xml如下