2023-09-16  阅读(108)
原文作者:王伟王胖胖 原文地址: https://blog.csdn.net/wangwei19871103/article/details/105351327

处理回滚流程图

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传播机制图

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AbstractPlatformTransactionManager的processRollback处理回滚

unexpectedRollback这个一般是false,除非是设置rollback-only=true,才是true,表示是全局的回滚标记。首先会进行回滚前回调,然后判断是否设置了保存点,比如NESTED会设置,要先回滚到保存点。如果状态是新的事务,那就进行回滚,如果不是新的,就设置一个回滚标记,内部是设置连接持有器回滚标记。然后回滚完成回调,根据事务状态信息,完成后数据清除,和线程的私有资源解绑,重置连接自动提交,隔离级别,是否只读,释放连接,恢复挂起事务等

    	private void processRollback(DefaultTransactionStatus status, boolean unexpected) {
    		try {
    			boolean unexpectedRollback = unexpected;//意外的回滚
    
    			try {
    				triggerBeforeCompletion(status);//回滚完成前回调
    				//有保存点回滚到保存点
    				if (status.hasSavepoint()) {
    					if (status.isDebug()) {
    						logger.debug("Rolling back transaction to savepoint");
    					}
    					status.rollbackToHeldSavepoint();
    				}
    				else if (status.isNewTransaction()) {//当前状态是一个新事务
    					if (status.isDebug()) {
    						logger.debug("Initiating transaction rollback");
    					}
    					doRollback(status);//进行回滚
    				}
    				else {
    					// Participating in larger transaction
    					if (status.hasTransaction()) {
    						if (status.isLocalRollbackOnly() || isGlobalRollbackOnParticipationFailure()) {
    							if (status.isDebug()) {
    								logger.debug("Participating transaction failed - marking existing transaction as rollback-only");
    							}
    							doSetRollbackOnly(status);//设置连接要回滚标记,也就是全局回滚
    						}
    						else {
    							if (status.isDebug()) {
    								logger.debug("Participating transaction failed - letting transaction originator decide on rollback");
    							}
    						}
    					}
    					else {
    						logger.debug("Should roll back transaction but cannot - no transaction available");
    					}
    					// Unexpected rollback only matters here if we're asked to fail early
    					if (!isFailEarlyOnGlobalRollbackOnly()) {
    						unexpectedRollback = false;
    					}
    				}
    			}
    			catch (RuntimeException | Error ex) {
    				triggerAfterCompletion(status, TransactionSynchronization.STATUS_UNKNOWN);
    				throw ex;
    			}
    			//回滚完成后回调
    			triggerAfterCompletion(status, TransactionSynchronization.STATUS_ROLLED_BACK);
    
    			// Raise UnexpectedRollbackException if we had a global rollback-only marker
    			if (unexpectedRollback) {
    				throw new UnexpectedRollbackException(
    						"Transaction rolled back because it has been marked as rollback-only");
    			}
    		}
    		finally {//根据事务状态信息,完成后数据清除,和线程的私有资源解绑,重置连接自动提交,隔离级别,是否只读,释放连接,恢复挂起事务等
    			cleanupAfterCompletion(status);
    		}
    	}

AbstractTransactionStatus的rollbackToHeldSavepoint回滚到保存点

如果设置了保存点的话,会进行处理,回滚到保存点,内部就是调用JDBC的连接回滚,释放保存点,其实没做什么,空的,最后清除保存点:

    	public void rollbackToHeldSavepoint() throws TransactionException {
    		Object savepoint = getSavepoint();
    		if (savepoint == null) {
    			throw new TransactionUsageException(
    					"Cannot roll back to savepoint - no savepoint associated with current transaction");
    		}
    		getSavepointManager().rollbackToSavepoint(savepoint);//回滚到保存点
    		getSavepointManager().releaseSavepoint(savepoint);//释放保存点,其实啥都没做
    		setSavepoint(null);//清除保存点
    	}

JdbcTransactionObjectSupport的rollbackToSavepoint回滚到保存点

内部就是获取连接对象,然后调用rollback回滚到保存点,然后重置连接持有器的回滚标记为false。所以这里不会影响外层的提交,否则外层提交的时候发现有回滚标记,会进行回滚的,这个在讲提交的时候会说到。

    	@Override
    	public void rollbackToSavepoint(Object savepoint) throws TransactionException {
    		ConnectionHolder conHolder = getConnectionHolderForSavepoint();
    		try {
    			conHolder.getConnection().rollback((Savepoint) savepoint);//回滚到保存点
    			conHolder.resetRollbackOnly();//重置回滚标记,不需要回滚
    		}
    		catch (Throwable ex) {
    			throw new TransactionSystemException("Could not roll back to JDBC savepoint", ex);
    		}
    	}

重置回滚标记:

202309162319366503.png

DataSourceTransactionManager的doRollback回滚

真正的回滚就是这里啦,也是获取到JDBC的连接,然后回滚。

    	@Override
    	protected void doRollback(DefaultTransactionStatus status) {
    		DataSourceTransactionObject txObject = (DataSourceTransactionObject) status.getTransaction();
    		Connection con = txObject.getConnectionHolder().getConnection();
    		if (status.isDebug()) {
    			logger.debug("Rolling back JDBC transaction on Connection [" + con + "]");
    		}
    		try {
    			con.rollback();//jdbc的回滚
    		}
    		catch (SQLException ex) {
    			throw new TransactionSystemException("Could not roll back JDBC transaction", ex);
    		}
    	}

DataSourceTransactionManager的doSetRollbackOnly设置回滚标记

如果既没有保存点,又不是新的事务,如果可以设置全局的回滚标记的话,就会设置。

    	@Override
    	protected void doSetRollbackOnly(DefaultTransactionStatus status) {
    		DataSourceTransactionObject txObject = (DataSourceTransactionObject) status.getTransaction();
    		if (status.isDebug()) {
    			logger.debug("Setting JDBC transaction [" + txObject.getConnectionHolder().getConnection() +
    					"] rollback-only");
    		}
    		txObject.setRollbackOnly();
    	}

DataSourceTransactionObject 的setRollbackOnly设置回滚标记

最终就是设置了连接持有器的回滚标记啦。

    		public void setRollbackOnly() {
    			getConnectionHolder().setRollbackOnly();
    		}

最后再进行cleanupAfterCompletion的清除处理,里面也涉及到很多东西,后面说。

好了,今天就到这里了,希望对学习理解有帮助,大神看见勿喷,仅为自己的学习理解,能力有限,请多包涵。

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