spring mvc+mybatis+多数据源切换

spring mvc+mybatis+多数据源切换 选取oracle,mysql作为例子切换数据源。oracle为默认数据源，在测试的action中，进行mysql和oracle的动态切换。 

web.xml 

<context-param>  
        <param-name>webAppRootKey</param-name>  
        <param-value>trac</param-value>  
    </context-param>  
  
    <!-- Spring的log4j监听器 -->  
    <listener>  
        <listener-class>org.springframework.web.util.Log4jConfigListener</listener-class>  
    </listener>  
  
    <!-- 字符集 过滤器 -->  
    <filter>  
        <filter-name>CharacterEncodingFilter</filter-name>  
        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>  
        <init-param>  
            <param-name>encoding</param-name>  
            <param-value>utf8</param-value>  
        </init-param>  
        <init-param>  
            <param-name>forceEncoding</param-name>  
            <param-value>true</param-value>  
        </init-param>  
    </filter>  
    <filter-mapping>  
        <filter-name>CharacterEncodingFilter</filter-name>  
        <url-pattern>/*</url-pattern>  
    </filter-mapping>  
  
    <!-- Spring view分发器 -->  
    <servlet>  
        <servlet-name>dispatcher</servlet-name>  
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>  
        <init-param>  
            <param-name>contextConfigLocation</param-name>  
            <param-value>/WEB-INF/dispatcher.xml</param-value>  
        </init-param>  
        <load-on-startup>1</load-on-startup>  
    </servlet>  
    <servlet-mapping>  
        <servlet-name>dispatcher</servlet-name>  
        <url-pattern>*.action</url-pattern>  
    </servlet-mapping>  
      
    <listener>  
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>  
    </listener>  

dispatcher.xml 

<mvc:annotation-driven />  
    <context:component-scan base-package="com.trac" />  
  
    <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver" />  
  
    <!-- freemarker config -->  
    <bean id="freemarkerConfig" class="org.springframework.web.servlet.view.freemarker.FreeMarkerConfigurer">  
        <property name="templateLoaderPath" value="/WEB-INF/freemarker/" />  
        <property name="freemarkerVariables">  
            <map>  
                <entry key="xml_escape" value-ref="fmXmlEscape" />  
            </map>  
        </property>  
        <property name="freemarkerSettings">  
            <props>  
                <prop key="defaultEncoding">UTF-8</prop>  
            </props>  
        </property>  
    </bean>  
  
    <bean id="fmXmlEscape" class="freemarker.template.utility.XmlEscape" />  
  
    <!-- View resolvers can also be configured with ResourceBundles or XML files.   
        If you need different view resolving based on Locale, you have to use the   
        resource bundle resolver. -->  
    <bean id="viewResolver" class="org.springframework.web.servlet.view.freemarker.FreeMarkerViewResolver">  
        <property name="exposeRequestAttributes" value="true" />  
        <property name="exposeSessionAttributes" value="true" />  
        <property name="exposeSpringMacroHelpers" value="true" />  
        <property name="contentType" value="text/html;charset=UTF-8" />  
        <property name="cache" value="true" />  
        <property name="prefix" value="" />  
        <property name="suffix" value=".ftl" />  
    </bean>  

applicationContext.xml 

<bean id="parentDataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">  
    </bean>  
      
    <bean id="mySqlDataSource" parent="parentDataSource">  
        <property name="driverClassName" value="com.mysql.jdbc.Driver"></property>  
        <property name="url" value="jdbc:mysql://localhost:3306/test"></property>  
        <property name="username" value="root"></property>  
        <property name="password" value="root"></property>  
    </bean>  
      
    <bean id="oracleDataSource" parent="parentDataSource">  
        <property name="driverClassName" value="oracle.jdbc.driver.OracleDriver"></property>  
        <property name="url" value="jdbc:oracle:thin:@10.16.17.40:1531:addb"></property>  
        <property name="username" value="trac"></property>  
        <property name="password" value="trac"></property>  
    </bean>  
      
    <bean id="dataSource" class="com.trac.dao.datasource.DataSources">  
        <property name="targetDataSources">  
            <map key-type="java.lang.String">  
                <entry value-ref="mySqlDataSource" key="MYSQL"></entry>  
                <entry value-ref="oracleDataSource" key="ORACLE"></entry>  
            </map>  
        </property>  
        <property name="defaultTargetDataSource" ref="oracleDataSource"></property>  
    </bean>  
  
    <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">  
        <property name="dataSource" ref="dataSource" />  
    </bean>  
  
    <!-- 创建SqlSessionFactory，同时指定数据源和mapper -->  
    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">  
        <property name="dataSource" ref="dataSource" />  
        <property name="mapperLocations" value="classpath*:com/trac/ibatis/dbcp/*.xml" />  
    </bean>  
用注解可以不上这段
  
    <bean id="sqlSession" class="org.mybatis.spring.SqlSessionTemplate">  
        <constructor-arg index="0" ref="sqlSessionFactory" />  
    </bean>  
  
    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">  
        <property name="basePackage" value="com.trac.dao" />  自己的DAO
    </bean>  

配置 parentDataSource 的父bean.再配置多个数据源继承这个父bean,对driverClass,url,username,password,等数据源连接参数进行各自的重写。例如 mySqlDataSource ，在 DataSources bean中注入所有要切换的数据源，并且设置默认的数据源。 

DataSourceInstances.java 

public class DataSourceInstances{  
    public static final String MYSQL="MYSQL";  
    public static final String ORACLE="ORACLE";  
}     
  
定义数据源的标识, 和applicationContext.xml中 DataSources 的 targetDataSources 的key对应  

DataSourceSwitch.java 

public class DataSourceSwitch{  
    private static final ThreadLocal contextHolder=new ThreadLocal();  
      
    public static void setDataSourceType(String dataSourceType){  
        contextHolder.set(dataSourceType);  
    }  
      
    public static String getDataSourceType(){  
        return (String) contextHolder.get();  
    }  
      
    public static void clearDataSourceType(){  
        contextHolder.remove();  
    }  
}  

DataSources.java 

import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;  
  
public class DataSources extends AbstractRoutingDataSource{  
  
    @Override  
    protected Object determineCurrentLookupKey() {  
        return DataSourceSwitch.getDataSourceType();  
    }  
  
}  
  
配置于applicationContext 中，线程局部变量ThreadLocal contextHolder 保存当前需要的数据源类型，当 DataSourceSwitch.setDataSourceType(DataSourceInstances.XXX) 保存当前需要的数据源类型的时候，DataSources 会从当前线程中查找线程变量的数据源类型，从而决定使用何种数据源  

TestAction.java