Spring3 整合MyBatis3 配置多数据源 动态选择SqlSessionFactory
一、摘要
上两篇文章分别介绍了Spring3.3 整合 Hibernate3、MyBatis3.2 配置多数据源/动态切换数据源 方法 和 Spring3 整合Hibernate3.5 动态切换SessionFactory (切换数据库方言),这篇文章将介绍Spring整合Mybatis 如何完成SqlSessionFactory的动态切换的。并且会简单的介绍下MyBatis整合Spring中的官方的相关代码。
Spring整合MyBatis切换SqlSessionFactory有两种方法,第一、 继承SqlSessionDaoSupport,重写获取SqlSessionFactory的方法。第二、继承SqlSessionTemplate 重写getSqlSessionFactory、getConfiguration和SqlSessionInterceptor这个拦截器。其中最为关键还是继承SqlSessionTemplate 并重写里面的方法。
而Spring整合MyBatis也有两种方式,一种是配置MapperFactoryBean,另一种则是利用MapperScannerConfigurer进行扫描接口或包完成对象的自动创建。相对来说后者更方便些。MapperFactoryBean继承了SqlSessionDaoSupport也就是动态切换SqlSessionFactory的第一种方法,我们需要重写和实现SqlSessionDaoSupport方法,或者是继承MapperFactoryBean来重写覆盖相关方法。如果利用MapperScannerConfigurer的配置整合来切换SqlSessionFactory,那么我们就需要继承SqlSessionTemplate,重写上面提到的方法。在整合的配置中很多地方都是可以注入SqlSessionTemplate代替SqlSessionFactory的注入的。因为SqlSessionTemplate的创建也是需要注入SqlSessionFactory的。
二、实现代码
1、继承SqlSessionTemplate 重写getSqlSessionFactory、getConfiguration和SqlSessionInterceptor
package com.hoo.framework.mybatis.support;import static java.lang.reflect.Proxy.newProxyInstance;import static org.apache.ibatis.reflection.ExceptionUtil.unwrapThrowable;import static org.mybatis.spring.SqlSessionUtils.closeSqlSession;import static org.mybatis.spring.SqlSessionUtils.getSqlSession;import static org.mybatis.spring.SqlSessionUtils.isSqlSessionTransactional;import java.lang.reflect.InvocationHandler;import java.lang.reflect.Method;import java.sql.Connection;import java.util.List;import java.util.Map;import org.apache.ibatis.exceptions.PersistenceException;import org.apache.ibatis.executor.BatchResult;import org.apache.ibatis.session.Configuration;import org.apache.ibatis.session.ExecutorType;import org.apache.ibatis.session.ResultHandler;import org.apache.ibatis.session.RowBounds;import org.apache.ibatis.session.SqlSession;import org.apache.ibatis.session.SqlSessionFactory;import org.mybatis.spring.MyBatisExceptionTranslator;import org.mybatis.spring.SqlSessionTemplate;import org.springframework.dao.support.PersistenceExceptionTranslator;import org.springframework.util.Assert;/*** <b>function:</b> 继承SqlSessionTemplate 重写相关方法* @author hoojo* @createDate 2013-10-18 下午03:07:46* @file CustomSqlSessionTemplate.java* @package com.hoo.framework.mybatis.support* @project SHMB* @blog http://blog.csdn.net/IBM_hoojo* @email hoojo_@126.com* @version 1.0*/public class CustomSqlSessionTemplate extends SqlSessionTemplate {private final SqlSessionFactory sqlSessionFactory;private final ExecutorType executorType;private final SqlSession sqlSessionProxy;private final PersistenceExceptionTranslator exceptionTranslator;private Map<Object, SqlSessionFactory> targetSqlSessionFactorys;private SqlSessionFactory defaultTargetSqlSessionFactory;public void setTargetSqlSessionFactorys(Map<Object, SqlSessionFactory> targetSqlSessionFactorys) {this.targetSqlSessionFactorys = targetSqlSessionFactorys;}public void setDefaultTargetSqlSessionFactory(SqlSessionFactory defaultTargetSqlSessionFactory) {this.defaultTargetSqlSessionFactory = defaultTargetSqlSessionFactory;}public CustomSqlSessionTemplate(SqlSessionFactory sqlSessionFactory) {this(sqlSessionFactory, sqlSessionFactory.getConfiguration().getDefaultExecutorType());}public CustomSqlSessionTemplate(SqlSessionFactory sqlSessionFactory, ExecutorType executorType) {this(sqlSessionFactory, executorType, new MyBatisExceptionTranslator(sqlSessionFactory.getConfiguration().getEnvironment().getDataSource(), true));}public CustomSqlSessionTemplate(SqlSessionFactory sqlSessionFactory, ExecutorType executorType,PersistenceExceptionTranslator exceptionTranslator) {super(sqlSessionFactory, executorType, exceptionTranslator);this.sqlSessionFactory = sqlSessionFactory;this.executorType = executorType;this.exceptionTranslator = exceptionTranslator;this.sqlSessionProxy = (SqlSession) newProxyInstance(SqlSessionFactory.class.getClassLoader(),new Class[] { SqlSession.class },new SqlSessionInterceptor());this.defaultTargetSqlSessionFactory = sqlSessionFactory;}@Overridepublic SqlSessionFactory getSqlSessionFactory() {SqlSessionFactory targetSqlSessionFactory = targetSqlSessionFactorys.get(CustomerContextHolder.getContextType());if (targetSqlSessionFactory != null) {return targetSqlSessionFactory;} else if (defaultTargetSqlSessionFactory != null) {return defaultTargetSqlSessionFactory;} else {Assert.notNull(targetSqlSessionFactorys, "Property 'targetSqlSessionFactorys' or 'defaultTargetSqlSessionFactory' are required");Assert.notNull(defaultTargetSqlSessionFactory, "Property 'defaultTargetSqlSessionFactory' or 'targetSqlSessionFactorys' are required");}return this.sqlSessionFactory;}@Overridepublic Configuration getConfiguration() {return this.getSqlSessionFactory().getConfiguration();}public ExecutorType getExecutorType() {return this.executorType;}public PersistenceExceptionTranslator getPersistenceExceptionTranslator() {return this.exceptionTranslator;}/*** {@inheritDoc}*/public <T> T selectOne(String statement) {return this.sqlSessionProxy.<T> selectOne(statement);}/*** {@inheritDoc}*/public <T> T selectOne(String statement, Object parameter) {return this.sqlSessionProxy.<T> selectOne(statement, parameter);}/*** {@inheritDoc}*/public <K, V> Map<K, V> selectMap(String statement, String mapKey) {return this.sqlSessionProxy.<K, V> selectMap(statement, mapKey);}/*** {@inheritDoc}*/public <K, V> Map<K, V> selectMap(String statement, Object parameter, String mapKey) {return this.sqlSessionProxy.<K, V> selectMap(statement, parameter, mapKey);}/*** {@inheritDoc}*/public <K, V> Map<K, V> selectMap(String statement, Object parameter, String mapKey, RowBounds rowBounds) {return this.sqlSessionProxy.<K, V> selectMap(statement, parameter, mapKey, rowBounds);}/*** {@inheritDoc}*/public <E> List<E> selectList(String statement) {return this.sqlSessionProxy.<E> selectList(statement);}/*** {@inheritDoc}*/public <E> List<E> selectList(String statement, Object parameter) {return this.sqlSessionProxy.<E> selectList(statement, parameter);}/*** {@inheritDoc}*/public <E> List<E> selectList(String statement, Object parameter, RowBounds rowBounds) {return this.sqlSessionProxy.<E> selectList(statement, parameter, rowBounds);}/*** {@inheritDoc}*/public void select(String statement, ResultHandler handler) {this.sqlSessionProxy.select(statement, handler);}/*** {@inheritDoc}*/public void select(String statement, Object parameter, ResultHandler handler) {this.sqlSessionProxy.select(statement, parameter, handler);}/*** {@inheritDoc}*/public void select(String statement, Object parameter, RowBounds rowBounds, ResultHandler handler) {this.sqlSessionProxy.select(statement, parameter, rowBounds, handler);}/*** {@inheritDoc}*/public int insert(String statement) {return this.sqlSessionProxy.insert(statement);}/*** {@inheritDoc}*/public int insert(String statement, Object parameter) {return this.sqlSessionProxy.insert(statement, parameter);}/*** {@inheritDoc}*/public int update(String statement) {return this.sqlSessionProxy.update(statement);}/*** {@inheritDoc}*/public int update(String statement, Object parameter) {return this.sqlSessionProxy.update(statement, parameter);}/*** {@inheritDoc}*/public int delete(String statement) {return this.sqlSessionProxy.delete(statement);}/*** {@inheritDoc}*/public int delete(String statement, Object parameter) {return this.sqlSessionProxy.delete(statement, parameter);}/*** {@inheritDoc}*/public <T> T getMapper(Class<T> type) {return getConfiguration().getMapper(type, this);}/*** {@inheritDoc}*/public void commit() {throw new UnsupportedOperationException("Manual commit is not allowed over a Spring managed SqlSession");}/*** {@inheritDoc}*/public void commit(boolean force) {throw new UnsupportedOperationException("Manual commit is not allowed over a Spring managed SqlSession");}/*** {@inheritDoc}*/public void rollback() {throw new UnsupportedOperationException("Manual rollback is not allowed over a Spring managed SqlSession");}/*** {@inheritDoc}*/public void rollback(boolean force) {throw new UnsupportedOperationException("Manual rollback is not allowed over a Spring managed SqlSession");}/*** {@inheritDoc}*/public void close() {throw new UnsupportedOperationException("Manual close is not allowed over a Spring managed SqlSession");}/*** {@inheritDoc}*/public void clearCache() {this.sqlSessionProxy.clearCache();}/*** {@inheritDoc}*/public Connection getConnection() {return this.sqlSessionProxy.getConnection();}/*** {@inheritDoc}* @since 1.0.2*/public List<BatchResult> flushStatements() {return this.sqlSessionProxy.flushStatements();}/*** Proxy needed to route MyBatis method calls to the proper SqlSession got from Spring's Transaction Manager It also* unwraps exceptions thrown by {@code Method#invoke(Object, Object...)} to pass a {@code PersistenceException} to* the {@code PersistenceExceptionTranslator}.*/private class SqlSessionInterceptor implements InvocationHandler {public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {final SqlSession sqlSession = getSqlSession(CustomSqlSessionTemplate.this.getSqlSessionFactory(),CustomSqlSessionTemplate.this.executorType,CustomSqlSessionTemplate.this.exceptionTranslator);try {Object result = method.invoke(sqlSession, args);if (!isSqlSessionTransactional(sqlSession, CustomSqlSessionTemplate.this.getSqlSessionFactory())) {// force commit even on non-dirty sessions because some databases require// a commit/rollback before calling close()sqlSession.commit(true);}return result;} catch (Throwable t) {Throwable unwrapped = unwrapThrowable(t);if (CustomSqlSessionTemplate.this.exceptionTranslator != null && unwrapped instanceof PersistenceException) {Throwable translated = CustomSqlSessionTemplate.this.exceptionTranslator.translateExceptionIfPossible((PersistenceException) unwrapped);if (translated != null) {unwrapped = translated;}}throw unwrapped;} finally {closeSqlSession(sqlSession, CustomSqlSessionTemplate.this.getSqlSessionFactory());}}}}重写后的getSqlSessionFactory方法会从我们配置的SqlSessionFactory集合targetSqlSessionFactorys或默认的defaultTargetSqlSessionFactory中获取Session对象。而改写的SqlSessionInterceptor 是这个MyBatis整合Spring的关键,所有的SqlSessionFactory对象的session都将在这里完成创建、提交、关闭等操作。所以我们改写这里的代码,在这里获取getSqlSessionFactory的时候,从多个SqlSessionFactory中获取我们设置的那个即可。
上面添加了targetSqlSessionFactorys、defaultTargetSqlSessionFactory两个属性来配置多个SqlSessionFactory对象和默认的SqlSessionFactory对象。
CustomerContextHolder 设置SqlSessionFactory的类型
package com.hoo.framework.mybatis.support;/*** <b>function:</b> 多数据源* @author hoojo* @createDate 2013-9-27 上午11:36:57* @file CustomerContextHolder.java* @package com.hoo.framework.spring.support* @project SHMB* @blog http://blog.csdn.net/IBM_hoojo* @email hoojo_@126.com* @version 1.0*/public abstract class CustomerContextHolder {public final static String SESSION_FACTORY_MYSQL = "mysql";public final static String SESSION_FACTORY_ORACLE = "oracle";private static final ThreadLocal<String> contextHolder = new ThreadLocal<String>();public static void setContextType(String contextType) {contextHolder.set(contextType);}public static String getContextType() {return contextHolder.get();}public static void clearContextType() {contextHolder.remove();}}
2、配置相关的文件applicationContext-session-factory.xml
<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"xmlns:aop="http://www.springframework.org/schema/aop"xmlns:tx="http://www.springframework.org/schema/tx"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans-3.2.xsdhttp://www.springframework.org/schema/aophttp://www.springframework.org/schema/aop/spring-aop-3.2.xsdhttp://www.springframework.org/schema/txhttp://www.springframework.org/schema/tx/spring-tx-3.2.xsd "><!-- 配置c3p0数据源 --><bean id="dataSourceOracle" class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close"><property name="driverClass" value="${datasource.driver}"/><property name="jdbcUrl" value="${datasource.url}"/><property name="user" value="${datasource.username}"/><property name="password" value="${datasource.password}"/><property name="acquireIncrement" value="${c3p0.acquireIncrement}"/><property name="initialPoolSize" value="${c3p0.initialPoolSize}"/><property name="minPoolSize" value="${c3p0.minPoolSize}"/><property name="maxPoolSize" value="${c3p0.maxPoolSize}"/><property name="maxIdleTime" value="${c3p0.maxIdleTime}"/><property name="idleConnectionTestPeriod" value="${c3p0.idleConnectionTestPeriod}"/><property name="maxStatements" value="${c3p0.maxStatements}"/><property name="numHelperThreads" value="${c3p0.numHelperThreads}"/><property name="preferredTestQuery" value="${c3p0.preferredTestQuery}"/><property name="testConnectionOnCheckout" value="${c3p0.testConnectionOnCheckout}"/></bean><bean id="dataSourceMySQL" class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close"><property name="driverClass" value="com.mysql.jdbc.Driver"/><property name="jdbcUrl" value="jdbc:mysql://172.31.108.178:3306/world?useUnicode=true&characterEncoding=UTF-8&zeroDateTimeBehavior=convertToNull"/><property name="user" value="root"/><property name="password" value="jp2011"/><property name="acquireIncrement" value="${c3p0.acquireIncrement}"/><property name="initialPoolSize" value="${c3p0.initialPoolSize}"/><property name="minPoolSize" value="${c3p0.minPoolSize}"/><property name="maxPoolSize" value="${c3p0.maxPoolSize}"/><property name="maxIdleTime" value="${c3p0.maxIdleTime}"/><property name="idleConnectionTestPeriod" value="${c3p0.idleConnectionTestPeriod}"/><property name="maxStatements" value="${c3p0.maxStatements}"/><property name="numHelperThreads" value="${c3p0.numHelperThreads}"/><property name="preferredTestQuery" value="${c3p0.preferredTestQuery}"/><property name="testConnectionOnCheckout" value="${c3p0.testConnectionOnCheckout}"/></bean><!-- 配置SqlSessionFactoryBean --><bean id="oracleSqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean"><property name="dataSource" ref="dataSourceOracle"/><property name="configLocation" value="classpath:mybatis.xml"/><!-- mapper和resultmap配置路径 --><property name="mapperLocations"><list><!-- 表示在com.hoo目录下的任意包下的resultmap包目录中,以-resultmap.xml或-mapper.xml结尾所有文件 --><value>classpath:com/hoo/framework/mybatis/mybatis-common.xml</value><value>classpath:com/hoo/**/resultmap/*-resultmap.xml</value><value>classpath:com/hoo/**/mapper/*-mapper.xml</value><value>classpath:com/hoo/**/mapper/**/*-mapper.xml</value></list></property></bean><!-- 配置SqlSessionFactoryBean --><bean id="mysqlSqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean"><property name="dataSource" ref="dataSourceMySQL"/><property name="configLocation" value="classpath:mybatis.xml"/><!-- mapper和resultmap配置路径 --><property name="mapperLocations"><list><!-- 表示在com.hoo目录下的任意包下的resultmap包目录中,以-resultmap.xml或-mapper.xml结尾所有文件 (oracle和mysql扫描的配置和路径不一样,如果是公共的都扫描 这里要区分下,不然就报错 找不到对应的表、视图)--><value>classpath:com/hoo/framework/mybatis/mybatis-common.xml</value><value>classpath:com/hoo/**/resultmap/*-mysql-resultmap.xml</value><value>classpath:com/hoo/**/mapper/*-mysql-mapper.xml</value><value>classpath:com/hoo/**/mapper/**/*-mysql-mapper.xml</value><value>classpath:com/hoo/**/mapper/**/multiple-datasource-mapper.xml</value></list></property></bean><!-- 配置自定义的SqlSessionTemplate模板,注入相关配置 --><bean id="sqlSessionTemplate" class="com.hoo.framework.mybatis.support.CustomSqlSessionTemplate"><constructor-arg ref="oracleSqlSessionFactory" /><property name="targetSqlSessionFactorys"><map><entry value-ref="oracleSqlSessionFactory" key="oracle"/><entry value-ref="mysqlSqlSessionFactory" key="mysql"/></map></property></bean><!-- 通过扫描的模式,扫描目录在com/hoo/任意目录下的mapper目录下,所有的mapper都需要继承SqlMapper接口的接口 --><bean class="org.mybatis.spring.mapper.MapperScannerConfigurer"><property name="basePackage" value="com.hoo.**.mapper"/><!-- 注意注入sqlSessionTemplate --><property name="sqlSessionTemplateBeanName" value="sqlSessionTemplate"/><property name="markerInterface" value="com.hoo.framework.mybatis.SqlMapper"/></bean></beans>上面的配置关键是在MapperScannerConfigurer中注入sqlSessionTemplate,这个要注意。当我们配置了多个SqlSessionFactoryBean的时候,就需要为MapperScannerConfigurer指定一个sqlSessionFactoryBeanName或是sqlSessionTemplateBeanName。一般情况下注入了sqlSessionTemplateBeanName对象,那sqlSessionFactory也就有值了。如果单独的注入了sqlSessionFactory那么程序会创建一个sqlSessionTemplate对象。我们可以看看代码SqlSessionFactoryDaoSupport对象的代码。如果你不喜欢使用扫描的方式,也可以注入sqlSessionTemplate或继承sqlSessionTemplate完成数据库操作。
public abstract class SqlSessionDaoSupport extends DaoSupport {private SqlSession sqlSession;private boolean externalSqlSession;public void setSqlSessionFactory(SqlSessionFactory sqlSessionFactory) {if (!this.externalSqlSession) {this.sqlSession = new SqlSessionTemplate(sqlSessionFactory);}}public void setSqlSessionTemplate(SqlSessionTemplate sqlSessionTemplate) {this.sqlSession = sqlSessionTemplate;this.externalSqlSession = true;}......这段代码很明显,如果注入了sqlSessionTemplate上面的注入也就不会执行了。如果没有注入sqlSessionTemplate,那么会自动new一个sqlSessionTemplate对象。
3、编写相关测试接口和实现的mapper.xml
package com.hoo.server.datasource.mapper;import java.util.List;import java.util.Map;import com.hoo.framework.mybatis.SqlMapper;/*** <b>function:</b> MyBatis 多数据源 测试查询接口* @author hoojo* @createDate 2013-10-10 下午04:18:08* @file MultipleDataSourceMapper.java* @package com.hoo.server.datasource.mapper* @project SHMB* @blog http://blog.csdn.net/IBM_hoojo* @email hoojo_@126.com* @version 1.0*/public interface MultipleDataSourceMapper extends SqlMapper {public List<Map<String, Object>> execute4MySQL() throws Exception;public List<Map<String, Object>> execute4Oracle() throws Exception;}multiple-datasource-mapper.xml
<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="com.hoo.server.datasource.mapper.MultipleDataSourceMapper"><select id="execute4Oracle" resultType="map"><![CDATA[SELECT*FROMdeviceInfo_tab t where rownum < 10]]></select><select id="execute4MySQL" resultType="map"><![CDATA[SELECT*FROMcity limit 2]]></select></mapper>上面分别查询oracle和mysql两个数据库中的table
4、测试代码
@Autowired@Qualifier("multipleDataSourceMapper")private MultipleDataSourceMapper mapper;@Testpublic void testMapper() {CustomerContextHolder.setContextType(CustomerContextHolder.SESSION_FACTORY_MYSQL);try {trace(mapper.execute4MySQL());} catch (Exception e1) {e1.printStackTrace();}CustomerContextHolder.setContextType(CustomerContextHolder.SESSION_FACTORY_ORACLE);try {trace(mapper.execute4Oracle());} catch (Exception e) {e.printStackTrace();}}运行后发现能够顺利查询出数据。
如果你是重写SqlSessionDaoSupport,那么方法如下
package com.hoo.framework.mybatis.support;import java.util.Map;import org.apache.ibatis.session.SqlSession;import org.apache.ibatis.session.SqlSessionFactory;import org.mybatis.spring.SqlSessionUtils;import org.mybatis.spring.support.SqlSessionDaoSupport;import org.springframework.beans.BeansException;import org.springframework.context.ApplicationContext;import org.springframework.context.ApplicationContextAware;/*** <b>function:</b> MyBatis 动态SqlSessionFactory* @author hoojo* @createDate 2013-10-14 下午02:32:19* @file DynamicSqlSessionDaoSupport.java* @package com.hoo.framework.mybatis.support* @project SHMB* @blog http://blog.csdn.net/IBM_hoojo* @email hoojo_@126.com* @version 1.0*/public class DynamicSqlSessionDaoSupport extends SqlSessionDaoSupport implements ApplicationContextAware {private ApplicationContext applicationContext;private Map<Object, SqlSessionFactory> targetSqlSessionFactorys;private SqlSessionFactory defaultTargetSqlSessionFactory;private SqlSession sqlSession;@Overridepublic final SqlSession getSqlSession() {SqlSessionFactory targetSqlSessionFactory = targetSqlSessionFactorys.get(CustomerContextHolder.getContextType());if (targetSqlSessionFactory != null) {setSqlSessionFactory(targetSqlSessionFactory);} else if (defaultTargetSqlSessionFactory != null) {setSqlSessionFactory(defaultTargetSqlSessionFactory);targetSqlSessionFactory = defaultTargetSqlSessionFactory;} else {targetSqlSessionFactory = (SqlSessionFactory) applicationContext.getBean(CustomerContextHolder.getContextType());setSqlSessionFactory(targetSqlSessionFactory);}this.sqlSession = SqlSessionUtils.getSqlSession(targetSqlSessionFactory);return this.sqlSession;}@Overrideprotected void checkDaoConfig() {//Assert.notNull(getSqlSession(), "Property 'sqlSessionFactory' or 'sqlSessionTemplate' are required");}public void setTargetSqlSessionFactorys(Map<Object, SqlSessionFactory> targetSqlSessionFactorys) {this.targetSqlSessionFactorys = targetSqlSessionFactorys;}public void setDefaultTargetSqlSessionFactory(SqlSessionFactory defaultTargetSqlSessionFactory) {this.defaultTargetSqlSessionFactory = defaultTargetSqlSessionFactory;}@Overridepublic void setApplicationContext(ApplicationContext applicationContext) throws BeansException {this.applicationContext = applicationContext;}}主要重写getSqlSession方法,上面获取SqlSessionFactory的方法。
重写好了后就可以配置这个对象,配置代码如下
//每一个DAO由继承SqlSessionDaoSupport全部改为DynamicSqlSessionDaoSupportpublic class UserMapperDaoImpl extends DynamicSqlSessionDaoSupport implements UserDao {public int addUser(User user) {return this.getSqlSession().insert("com.hoo.user.dao.UserDao.addUser", user);}}在上面的配置文件中加入配置<bean id="baseDao" class="com.hoo.framework.mybatis.support.DynamicSqlSessionDaoSupport" abstract="true" lazy-init="true"><property name="targetSqlSessionFactorys"><map><entry value-ref="oracleSqlSessionFactory" key="oracle"/><entry value-ref="mysqlSqlSessionFactory" key="mysql"/></map></property><property name="defaultTargetSqlSessionFactory" ref="oracleSqlSessionFactory"/></bean><bean id="userMapperDao" class="com.hoo.user.dao.impl.UserMapperDaoImpl" parent="baseDao"/>就这样也可以利用DynamicSqlSessionDaoSupport来完成动态切换sqlSessionFactory对象,只需用在注入userMapperDao调用方法的时候设置下CustomerContextHolder的contextType即可。
三、总结
为了实现这个功能看了mybatis-spring-1.2.0.jar这个包的部分源代码,代码内容不是很多。所以看了下主要的代码,下面做些简单的介绍。
MapperScannerConfigurer这个类就是我们要扫描的Mapper接口的类,也就是basePackage中继承markerInterface配置的接口。可以看看ClassPathBeanDefinitionScanner、ClassPathMapperScanner中的doScan这个方法。它会扫描basePackage这个包下所有接口,在ClassPathScanningCandidateComponentProvider中有这个方法findCandidateComponents,它会找到所有的BeanDefinition。
最重要的一点是ClassPathMapperScanner中的doScan这个方法它会给这些接口创建一个MapperFactoryBean。并且会检查sqlSessionFactory和sqlSessionTemplate对象的注入情况。
所以我们配置扫描的方式也就相当于我们在配置文件中给每一个Mapper配置一个MapperFactoryBean一样。而这个MapperFactoryBean又继承SqlSessionDaoSupport。所以当初我想重写MapperScannerConfigurer中的postProcessBeanDefinitionRegistry方法,然后重写方法中的ClassPathMapperScanner中的doScan方法,将definition.setBeanClass(MapperFactoryBean.class);改成自己定义的MapperFactoryBean。最后以失败告终,因为这里是Spring装载扫描对象的时候都已经为这些对象创建好了代理、设置好了mapperInterface和注入需要的类。所以在调用相关操作数据库的API方法的时候,设置对应的SqlSessionFactory也是无效的。
辗转反侧我看到了SqlSessionTemplate这个类,它的功能相当于SqlSessionDaoSupport的实现类MapperFactoryBean。最为关键的是SqlSessionTemplate有一个拦截器SqlSessionInterceptor,它复制所有SqlSession的创建、提交、关闭,而且是在每个方法之前。这点在上面也提到过了!所以我们只需要在SqlSessionInterceptor方法中获取SqlSessionFactory的时候,在这之前调用下CustomerContextHolder.setContextType方法即可完成数据库的SqlSessionFactory的切换。而在MapperScannerConfigurer提供了注入SqlSessionFactory和sqlSessionTemplate的方法,如果注入了SqlSessionFactory系统将会new一个sqlSessionTemplate,而注入了sqlSessionTemplate就不会创建其他对象(见下面代码)。所以我们配置一个sqlSessionTemplate并注入到MapperScannerConfigurer中,程序将会使用这个sqlSessionTemplate。本文最后的实现方式就是这样完成的。
public void setSqlSessionFactory(SqlSessionFactory sqlSessionFactory) {if (!this.externalSqlSession) {this.sqlSession = new SqlSessionTemplate(sqlSessionFactory);}}public void setSqlSessionTemplate(SqlSessionTemplate sqlSessionTemplate) {this.sqlSession = sqlSessionTemplate;this.externalSqlSession = true;}
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