一、摘要
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
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;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; } public <T> T selectOne(String statement) { return this.sqlSessionProxy.<T> selectOne(statement); } public <T> T selectOne(String statement, Object parameter) { return this.sqlSessionProxy.<T> selectOne(statement, parameter); } public <K, V> Map<K, V> selectMap(String statement, String mapKey) { return this.sqlSessionProxy.<K, V> selectMap(statement, mapKey); } public <K, V> Map<K, V> selectMap(String statement, Object parameter, String mapKey) { return this.sqlSessionProxy.<K, V> selectMap(statement, parameter, mapKey); } 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); } public <E> List<E> selectList(String statement) { return this.sqlSessionProxy.<E> selectList(statement); } public <E> List<E> selectList(String statement, Object parameter) { return this.sqlSessionProxy.<E> selectList(statement, parameter); } public <E> List<E> selectList(String statement, Object parameter, RowBounds rowBounds) { return this.sqlSessionProxy.<E> selectList(statement, parameter, rowBounds); } public void select(String statement, ResultHandler handler) { this.sqlSessionProxy.select(statement, handler); } public void select(String statement, Object parameter, ResultHandler handler) { this.sqlSessionProxy.select(statement, parameter, handler); } public void select(String statement, Object parameter, RowBounds rowBounds, ResultHandler handler) { this.sqlSessionProxy.select(statement, parameter, rowBounds, handler); } public int insert(String statement) { return this.sqlSessionProxy.insert(statement); } public int insert(String statement, Object parameter) { return this.sqlSessionProxy.insert(statement, parameter); } public int update(String statement) { return this.sqlSessionProxy.update(statement); } public int update(String statement, Object parameter) { return this.sqlSessionProxy.update(statement, parameter); } public int delete(String statement) { return this.sqlSessionProxy.delete(statement); } public int delete(String statement, Object parameter) { return this.sqlSessionProxy.delete(statement, parameter); } public <T> T getMapper(Class<T> type) { return getConfiguration().getMapper(type, this); } public void commit() { throw new UnsupportedOperationException("Manual commit is not allowed over a Spring managed SqlSession"); } public void commit(boolean force) { throw new UnsupportedOperationException("Manual commit is not allowed over a Spring managed SqlSession"); } public void rollback() { throw new UnsupportedOperationException("Manual rollback is not allowed over a Spring managed SqlSession"); } public void rollback(boolean force) { throw new UnsupportedOperationException("Manual rollback is not allowed over a Spring managed SqlSession"); } public void close() { throw new UnsupportedOperationException("Manual close is not allowed over a Spring managed SqlSession"); } public void clearCache() { this.sqlSessionProxy.clearCache(); } public Connection getConnection() { return this.sqlSessionProxy.getConnection(); } public List<BatchResult> flushStatements() { return this.sqlSessionProxy.flushStatements(); } 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()); } } }}免责声明：
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