spring mvc+mybatis+多数据源切换

转自：http://leoannto.iteye.com/blog/1624704

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 

@Controller
@SuppressWarnings("unused")
public class TestAction {
@Autowired
    TestMapper testMapper;

   @RequestMapping("/test.action")
    public ModelAndView test(
            HttpServletRequest request,
            HttpServletResponse resp){
        ModelAndView model = new ModelAndView("test");
        model.addObject("test1", "这是一个测试,获取默认数据连接MYSQL:"+testMapper.test());
        DataSourceSwitch.setDataSourceType(DataSourceInstances.ORACLE);
        model.addObject("test2", "这是一个测试,获取数据连接ORACLE:"+testMapper.test());
        DataSourceSwitch.setDataSourceType(DataSourceInstances.MYSQL);
        model.addObject("test3", "这是一个测试,获取数据连接MYSQL:"+testMapper.test());
        return model;
    }
}