mybatis于spring事务结合

mybatis如何和spring的事务结合的

PlatformTransactionManager （平台）事务管理器

public interface PlatformTransactionManager {
  // 根据指定的传播行为，返回当前活动的事务或创建一个新事务。
  TransactionStatus getTransaction(TransactionDefinition definition) throws TransactionException;    
  // 使用事务目前的状态提交事务
  void commit(TransactionStatus status) throws TransactionException;    
  // 对执行的事务进行回滚  
  void rollback(TransactionStatus status) throws TransactionException;    
}

TransactionDefinition 事务定义信息(事务隔离级别、传播行为、超时、只读、回滚规则

TransactionStatus 事务运行状态

spring对方法加有@Transactional的方法进行拦截

org.springframework.transaction.interceptor.TransactionInterceptor#invoke
org.springframework.transaction.interceptor.TransactionAspectSupport#invokeWithinTransaction
org.springframework.jdbc.datasource.DataSourceTransactionManager#doBegin
protected void doBegin(Object transaction, TransactionDefinition definition) {
  //将 Connection 放入到 TransactionSynchronizationManager
  if (txObject.isNewConnectionHolder()) {
    TransactionSynchronizationManager.bindResource(obtainDataSource(), txObject.getConnectionHolder());
  }
}

mybatis中拿到和spring管理的Connection

// org.apache.ibatis.executor.SimpleExecutor#prepareStatement
protected Connection getConnection(Log statementLog) throws SQLException {
  //从 SpringManagedTransaction拿到 connection
  Connection connection = transaction.getConnection();
}
// org.mybatis.spring.transaction.SpringManagedTransaction#openConnection
private void openConnection() throws SQLException {
  //从Spring管理的连接中拿到 connection
  this.connection = DataSourceUtils.getConnection(this.dataSource);
}
//org.springframework.jdbc.datasource.DataSourceUtils#doGetConnection
public static Connection doGetConnection(DataSource dataSource) throws SQLException {
    //从TransactionSynchronizationManager拿到数据库连接
        ConnectionHolder conHolder = (ConnectionHolder)TransactionSynchronizationManager.getResource(dataSource);
}

但是我们知道我们使用mybatis-spring的时候使用了SqlSessionTemplate这里也会进行事务操作比如
对Mapper代理对象调用进行拦截

// org.mybatis.spring.SqlSessionTemplate.SqlSessionInterceptor
private class SqlSessionInterceptor implements InvocationHandler {
  @Override
  public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
    //...获取SqlSession
    SqlSession sqlSession = getSqlSession(SqlSessionTemplate.this.sqlSessionFactory,
        SqlSessionTemplate.this.executorType, SqlSessionTemplate.this.exceptionTranslator);
    try {
      //调用SqlSession来执行sql
      Object result = method.invoke(sqlSession, args);
      //判断当前sqlSession是否在当前事物当中
      if (!isSqlSessionTransactional(sqlSession, SqlSessionTemplate.this.sqlSessionFactory)) {
            sqlSession.commit(true);
      }
      return result;
    } catch (Throwable t) {
      //...省略方法
    } finally {
      if (sqlSession != null) {
        closeSqlSession(sqlSession, SqlSessionTemplate.this.sqlSessionFactory);
      }
    }
  }
}
// org.mybatis.spring.SqlSessionUtils#isSqlSessionTransactional
public static boolean isSqlSessionTransactional(SqlSession session, SqlSessionFactory sessionFactory) {
  SqlSessionHolder holder = (SqlSessionHolder)TransactionSynchronizationManager.getResource(sessionFactory);
  return (holder != null) && (holder.getSqlSession() == session);
}
// org.mybatis.spring.SqlSessionUtils#closeSqlSession
public static void closeSqlSession(SqlSession session, SqlSessionFactory sessionFactory) {
  SqlSessionHolder holder = (SqlSessionHolder) TransactionSynchronizationManager.getResource(sessionFactory);
  if ((holder != null) && (holder.getSqlSession() == session)) {
    holder.released();
  } else {
    session.close();
  }
}