一、摘要
這篇文章將介紹Spring整合Mybatis 如何完成SqlSessionFactory的動態切換的。并且會簡單的介紹下MyBatis整合Spring中的官方的相關代碼。
Spring整合MyBatis切換SqlSessionFactory有兩種方法
第一、 繼承SqlSessionDaoSupport，重寫獲取SqlSessionFactory的方法。
第二、繼承SqlSessionTemplate 重寫getSqlSessionFactory、getConfiguration和SqlSessionInterceptor這個攔截器。其中最為關鍵還是繼承SqlSessionTemplate 并重寫里面的方法。
而Spring整合MyBatis也有兩種方式，一種是配置MapperFactoryBean，另一種則是利用MapperScannerConfigurer進行掃描接口或包完成對象的自動創建。相對來說后者更方便些。
MapperFactoryBean繼承了SqlSessionDaoSupport也就是動態切換SqlSessionFactory的第一種方法，我們需要重寫和實現SqlSessionDaoSupport方法，或者是繼承MapperFactoryBean來重寫覆蓋相關方法。如果利用MapperScannerConfigurer的配置整合來切換SqlSessionFactory，那么我們就需要繼承SqlSessionTemplate，重寫上面提到的方法。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。因為SqlSessionTemplate的創建也是需要注入SqlSessionFactory的。
二、實現代碼
1、繼承SqlSessionTemplate 重寫getSqlSessionFactory、getConfiguration和SqlSessionInterceptor
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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> 繼承SqlSessionTemplate 重寫相關方法 * @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 [email protected] * @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; } @Override public 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; } @Override public 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()); } } }} |
重寫后的getSqlSessionFactory方法會從我們配置的SqlSessionFactory集合targetSqlSessionFactorys或默認的defaultTargetSqlSessionFactory中獲取Session對象。而改寫的SqlSessionInterceptor 是這個MyBatis整合Spring的關鍵，所有的SqlSessionFactory對象的session都將在這里完成創建、提交、關閉等操作。所以我們改寫這里的代碼，在這里獲取getSqlSessionFactory的時候，從多個SqlSessionFactory中獲取我們設置的那個即可。
上面添加了targetSqlSessionFactorys、defaultTargetSqlSessionFactory兩個屬性來配置多個SqlSessionFactory對象和默認的SqlSessionFactory對象。
CustomerContextHolder 設置SqlSessionFactory的類型
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package com.hoo.framework.mybatis.support;/** * <b>function:</b> 多數據源 * @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 [email protected] * @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、配置相關的文件applicationContext-session-factory.xml
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<?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/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.2.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd "> <!-- 配置c3p0數據源 --> <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配置路徑 --> <property name="mapperLocations"> <list> <!-- 表示在com.hoo目錄下的任意包下的resultmap包目錄中，以-resultmap.xml或-mapper.xml結尾所有文件 --> <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配置路徑 --> <property name="mapperLocations"> <list> <!-- 表示在com.hoo目錄下的任意包下的resultmap包目錄中，以-resultmap.xml或-mapper.xml結尾所有文件 （oracle和mysql掃描的配置和路徑不一樣，如果是公共的都掃描 這里要區分下，不然就報錯 找不到對應的表、視圖）--> <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> <!-- 配置自定義的SqlSessionTemplate模板，注入相關配置 --> <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> <!-- 通過掃描的模式，掃描目錄在com/hoo/任意目錄下的mapper目錄下，所有的mapper都需要繼承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> |
上面的配置關鍵是在MapperScannerConfigurer中注入sqlSessionTemplate，這個要注意。當我們配置了多個SqlSessionFactoryBean的時候，就需要為MapperScannerConfigurer指定一個sqlSessionFactoryBeanName或是sqlSessionTemplateBeanName。一般情況下注入了sqlSessionTemplateBeanName對象，那sqlSessionFactory也就有值了。如果單獨的注入了sqlSessionFactory那么程序會創建一個sqlSessionTemplate對象。我們可以看看代碼SqlSessionFactoryDaoSupport對象的代碼。如果你不喜歡使用掃描的方式，也可以注入sqlSessionTemplate或繼承sqlSessionTemplate完成數據庫操作。
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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; }...... |
這段代碼很明顯，如果注入了sqlSessionTemplate上面的注入也就不會執行了。如果沒有注入sqlSessionTemplate，那么會自動new一個sqlSessionTemplate對象。
3、編寫相關測試接口和實現的mapper.xml
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package com.hoo.server.datasource.mapper;import java.util.List;import java.util.Map;import com.hoo.framework.mybatis.SqlMapper;/** * <b>function:</b> MyBatis 多數據源 測試查詢接口 * @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 [email protected] * @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 * FROM deviceInfo_tab t where rownum < 10 ]]> </select> <select id="execute4MySQL" resultType="map"> <![CDATA[ SELECT * FROM city limit 2 ]]> </select></mapper> |
上面分別查詢oracle和mysql兩個數據庫中的table
4、測試代碼
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@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(); }} |
運行后發現能夠順利查詢出數據。
如果你是重寫SqlSessionDaoSupport，那么方法如下
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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 動態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 [email protected] * @version 1.0 */public class DynamicSqlSessionDaoSupport extends SqlSessionDaoSupport implements ApplicationContextAware { private ApplicationContext applicationContext; private Map<Object, SqlSessionFactory> targetSqlSessionFactorys; private SqlSessionFactory defaultTargetSqlSessionFactory; private SqlSession sqlSession; @Override public 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; } @Override protected 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; } @Override public void setApplicationContext(ApplicationContext applicationContext) throws BeansException { this.applicationContext = applicationContext; }} |
主要重寫getSqlSession方法，上面獲取SqlSessionFactory的方法。
重寫好了后就可以配置這個對象，配置代碼如下
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//每一個DAO由繼承SqlSessionDaoSupport全部改為DynamicSqlSessionDaoSupport public 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
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<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"/> |
就這樣也可以利用DynamicSqlSessionDaoSupport來完成動態切換sqlSessionFactory對象，只需用在注入userMapperDao調用方法的時候設置下CustomerContextHolder的contextType即可。
三、總結
為了實現這個功能看了mybatis-spring-1.2.0.jar這個包的部分源代碼，代碼內容不是很多。所以看了下主要的代碼，下面做些簡單的介紹。
MapperScannerConfigurer這個類就是我們要掃描的Mapper接口的類，也就是basePackage中繼承markerInterface配置的接口。可以看看ClassPathBeanDefinitionScanner、ClassPathMapperScanner中的doScan這個方法。它會掃描basePackage這個包下所有接口，在ClassPathScanningCandidateComponentProvider中有這個方法findCandidateComponents，它會找到所有的BeanDefinition。
最重要的一點是ClassPathMapperScanner中的doScan這個方法它會給這些接口創建一個MapperFactoryBean。并且會檢查sqlSessionFactory和sqlSessionTemplate對象的注入情況。
image 所以我們配置掃描的方式也就相當于我們在配置文件中給每一個Mapper配置一個MapperFactoryBean一樣。而這個MapperFactoryBean又繼承SqlSessionDaoSupport。所以當初我想重寫MapperScannerConfigurer中的postProcessBeanDefinitionRegistry方法，然后重寫方法中的ClassPathMapperScanner中的doScan方法，將definition.setBeanClass(MapperFactoryBean.class);改成自己定義的MapperFactoryBean。最后以失敗告終，因為這里是Spring裝載掃描對象的時候都已經為這些對象創建好了代理、設置好了mapperInterface和注入需要的類。所以在調用相關操作數據庫的API方法的時候，設置對應的SqlSessionFactory也是無效的。
輾轉反側我看到了SqlSessionTemplate這個類，它的功能相當于SqlSessionDaoSupport的實現類MapperFactoryBean。最為關鍵的是SqlSessionTemplate有一個攔截器SqlSessionInterceptor，它復制所有SqlSession的創建、提交、關閉，而且是在每個方法之前。這點在上面也提到過了！所以我們只需要在SqlSessionInterceptor方法中獲取SqlSessionFactory的時候，在這之前調用下CustomerContextHolder.setContextType方法即可完成數據庫的SqlSessionFactory的切換。而在MapperScannerConfigurer提供了注入SqlSessionFactory和sqlSessionTemplate的方法，如果注入了SqlSessionFactory系統將會new一個sqlSessionTemplate，而注入了sqlSessionTemplate就不會創建其他對象（見下面代碼）。所以我們配置一個sqlSessionTemplate并注入到MapperScannerConfigurer中，程序將會使用這個sqlSessionTemplate。本文最后的實現方式就是這樣完成的。
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public void setSqlSessionFactory(SqlSessionFactory sqlSessionFactory) { if (!this.externalSqlSession) { this.sqlSession = new SqlSessionTemplate(sqlSessionFactory); }}public void setSqlSessionTemplate(SqlSessionTemplate sqlSessionTemplate) { this.sqlSession = sqlSessionTemplate; this.externalSqlSession = true;} |
以上所述是小編給大家介紹的Spring3 整合MyBatis3 配置多數據源動態選擇SqlSessionFactory詳細教程，希望對大家有所幫助，如果大家有任何疑問請給我留言，小編會及時回復大家的。在此也非常感謝大家對服務器之家網站的支持！
原文鏈接：http://www.blogjava.net/hoojo/archive/2013/10/22/405488.html
