Ibatis 事务 | 易学教程

一基于JDBC的事务

针对的是一个JDBC连接实现，不能跨多个数据库连接。如两个操作分别由两个不同的Connection执行，则不能实现

事例：

    public static void main(String[] args) throws SQLException, IOException {
        // TODO Auto-generated method stub
        Reader reader = Resources.getResourceAsReader("SqlMapConfig.xml");
        SqlMapClient sqlMapClient = SqlMapClientBuilder.buildSqlMapClient(reader);
        try{
            sqlMapClient.startTransaction();
            
            User user = (User) sqlMapClient.queryForObject("getUser", "test");
            System.out.println("id=" + user.getId());    
            
            sqlMapClient.commitTransaction();
        }finally{
            //如果出现异常或没有提交，会进行roll back
            sqlMapClient.endTransaction();
        }
    }

内部实现原理

  MappedStatement ms = getMappedStatement(id);
    Transaction trans = getTransaction(sessionScope);
    boolean autoStart = trans == null;　　//调用sqlMapClient.startTransaction();后，会生成一个Transaction ，autoStart为false,不自动提交

    try {
      trans = autoStartTransaction(sessionScope, autoStart, trans);

      StatementScope statementScope = beginStatementScope(sessionScope, ms);
      try {
        object = ms.executeQueryForObject(statementScope, trans, paramObject, resultObject);
      } finally {
        endStatementScope(statementScope);
      }

      autoCommitTransaction(sessionScope, autoStart);
    } finally {
      autoEndTransaction(sessionScope, autoStart);
    }

//sqlMapClient.commitTransaction();对应实现

 public void commit(SessionScope sessionScope) throws SQLException, TransactionException {
    Transaction trans = sessionScope.getTransaction();
    TransactionState state = sessionScope.getTransactionState();
    if (state == TransactionState.STATE_USER_PROVIDED) {
      throw new TransactionException("TransactionManager could not commit.  " +
          "A user provided connection is currently being used by this session.  " +
          "You must call the commit() method of the Connection directly.  " +
          "The calling .setUserConnection (null) will clear the user provided transaction.");
    } else if (state != TransactionState.STATE_STARTED && state != TransactionState.STATE_COMMITTED ) {
      throw new TransactionException("TransactionManager could not commit.  No transaction is started.");
    }
    if (sessionScope.isCommitRequired() || config.isForceCommit()) {
      trans.commit();//提交事务
      sessionScope.setCommitRequired(false);
    }
    sessionScope.setTransactionState(TransactionState.STATE_COMMITTED);
  }

// sqlMapClient.endTransaction(); 对应实现

  if (trans != null) {
        try {
          if (state != TransactionState.STATE_COMMITTED) {//如果异常、或没提交 都会进行回滚
            if (sessionScope.isCommitRequired() || config.isForceCommit()) {
              trans.rollback();
              sessionScope.setCommitRequired(false);
            }
          }
        } finally {
          sessionScope.closePreparedStatements();
          trans.close();
        }
      }

二、基于JTA的事务

　　JTA提供了跨数据库连接（或其他JTA资源）的事务管理能力。这一点是与JDBC Transaction最大的差异。

　　后续。。。

来源：https://www.cnblogs.com/xuruhong/p/3271735.html

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