spring mvc+mybatis+多数据源切换

springmvc+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>

	<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" />
	</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DataSourcesbean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;
	}
}