mybatis中事务的管理和集成spring后如何将事务交给spring管理

　　　1.mybatis中事务的管理

　　　　SqlSessionFactory开启一个SqlSession后，会给当前sqlsession注入事务工厂TransactionFactory：

　　　　

private SqlSession openSessionFromDataSource(ExecutorType execType, TransactionIsolationLevel level, boolean autoCommit) {    
  Transaction tx = null;
try {
      final Environment environment = configuration.getEnvironment();
      final TransactionFactory transactionFactory = getTransactionFactoryFromEnvironment(environment);
      tx = transactionFactory.newTransaction(environment.getDataSource(), level, autoCommit);
      final Executor executor = configuration.newExecutor(tx, execType);
      return new DefaultSqlSession(configuration, executor, autoCommit);
    } catch (Exception e) {
      closeTransaction(tx); // may have fetched a connection so lets call close()
      throw ExceptionFactory.wrapException("Error opening session.  Cause: " + e, e);
    } finally {
      ErrorContext.instance().reset();
    }
  }

　　
//事务的生产交给TransactionFactory

  private TransactionFactory getTransactionFactoryFromEnvironment(Environment environment) {
    if (environment == null || environment.getTransactionFactory() == null) {
      return new ManagedTransactionFactory();
    }
    return environment.getTransactionFactory();
  }

所以mybatis事务的生产由TransactionFactory生产，该类是个接口，而具体实现才是执行真正逻辑的地方，在spring集成mybatis中，SpringManagedTransactionFactory实现了该接口，由此将mybatis的事务管理交给了spring进行管理

实现交接的逻辑：

  <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource"/>
        <property name="mapperLocations" value="classpath*:*.xml"/>
    </bean>

在spring中配置的SqlSessionFactoryBean会执行afterPropertiesSet方法，该方法会初始化SqlsessionFactory,并且设置TransactionFactory为SpringManagedTransactionFactory

 <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <property name="basePackage" value="com.*.**"/>
        <property name="sqlSessionFactoryBeanName" value="sqlSessionFactory"/>
    </bean>

而MapperScannerConfigurer会执行postProcessBeanDefinitionRegistry方法，实现Mapper接口的代理，并将代理对象交给spring容器管理