ibatis源码浅析- 事务_ibatis sessionscope-优快云博客

ibatis默认提供四种事务 transaction 类图

ExternalTransactionConfig ：commit rollbak方法都是个空实现 spring默认使用的这个

UserProvidedTransaction ：支持外部Connection 可以和jdbc混合使用

JdbcTransaction ：原生jdbc事务

JtaTransaction：分布式事务

TransactionConfig 主要负责创建事务对象每一个Transaction都有一个TransactionConfig TransactionConfig类图

事务控制实例代码

		try {
			sqlmapclient.startTransaction ();
			.....
			sqlmapclient.commitTransaction ();
		} finally {
			sqlmapclient.endTransaction ();
		}

startTransaction方法：

根据sqlMapConfig配置调用TransactionManager类中的begin方法创建一个新的事务具体事务的创建由TransactionConfig接口的实现类完成

创建完成后将事务(Transaction) 保存到SessionScope中并设置当前sessionScope中的TransactionState为STATE_STARTED状态

SssionScope简单理解为ibatis上下文对象它与SqlMapSession对象绑定而SqlMapSession对象与当前线程绑定 SssionScope它持有当前Transaction, TransactionState

TransactionManager begin方法

	public void begin(SessionScope sessionScope, int transactionIsolation) throws SQLException, TransactionException {
		// .. 省略
		//TransactionConfig 创建一个新的Transaction
		trans = config.newTransaction(transactionIsolation);
		sessionScope.setCommitRequired(false);
		//当前事务对象保存到sessionScope
		sessionScope.setTransaction(trans);
		//设置当前事务状态
		sessionScope.setTransactionState(TransactionState.STATE_STARTED);
	}

JdbcTransactionConfig newTransaction方法

  public Transaction newTransaction(int transactionIsolation) {
	    return new JdbcTransaction(dataSource, transactionIsolation);
  }

commitTransaction 方法

间接的调用了TrasactionManager的commit方法提交事务如果提交成功设置事务状态为已提交状态

TransactionManager commit方法

	public void commit(SessionScope sessionScope) throws SQLException, TransactionException {
		Transaction trans = sessionScope.getTransaction();
		TransactionState state = sessionScope.getTransactionState();
		//..略
		//isCommitRequired 强制提交 可能出现异常
		if (sessionScope.isCommitRequired() || config.isForceCommit()) {
			//提交事务
			trans.commit();
			sessionScope.setCommitRequired(false);
		}
		//如果trans.commit()执行失败 这句不会执行 设置状态为已提交状态
		sessionScope.setTransactionState(TransactionState.STATE_COMMITTED);
	}

JdbcTransaction commit方法

  public void commit() throws SQLException, TransactionException {
    if (connection != null) {
      connection.commit();
    }
  }

endTransaction 收尾工作

①.根据commitTransaction阶段提交的事务状态判断是不是需要回滚 ,

②.关闭数据库连接 , 清理当前线程的sessionScope

TransactionManager end 方法

	public void end(SessionScope sessionScope) throws SQLException, TransactionException {
		//从SessionScope获取Transaction  TransactionState
		Transaction trans = sessionScope.getTransaction();
		TransactionState state = sessionScope.getTransactionState();
		//...略
		try {
			if (trans != null) {
				try {
					//如果不是已提交状态  执行回滚操作
					if (state != TransactionState.STATE_COMMITTED) {
						if (sessionScope.isCommitRequired() || config.isForceCommit()) {
							//执行回滚操作
							trans.rollback();
							sessionScope.setCommitRequired(false);
						}
					}
				} finally {
					//清理preparedStatements map集合 关闭PreparedStatement
					sessionScope.closePreparedStatements();
					//关闭当前Connection
					trans.close();
				}
			}
		} finally {
			sessionScope.setTransaction(null);
			//重新设置事务状态 为结束状态
			sessionScope.setTransactionState(TransactionState.STATE_ENDED);
		}
	}

JdbcTransaction

rollback方法

  public void rollback() throws SQLException, TransactionException {
    if (connection != null) {
      connection.rollback();
    }
  }

close方法关闭当前数据库连接

  public void close() throws SQLException, TransactionException {
    if (connection != null) {
      try {
        isolationLevel.restoreIsolationLevel(connection);
      } finally {
        connection.close();
        connection = null;
      }
    }
  }