Spring 5.x 源码之旅六十七深入AOP事务原理四

创建事务信息流程图

处理回滚流程图

传播机制图

AbstractPlatformTransactionManager的prepareSynchronization同步状态

设置各种线程私有变量的状态。

	protected void prepareSynchronization(DefaultTransactionStatus status, TransactionDefinition definition) {
		if (status.isNewSynchronization()) {
			TransactionSynchronizationManager.setActualTransactionActive(status.hasTransaction());
			TransactionSynchronizationManager.setCurrentTransactionIsolationLevel(
					definition.getIsolationLevel() != TransactionDefinition.ISOLATION_DEFAULT ?
							definition.getIsolationLevel() : null);
			TransactionSynchronizationManager.setCurrentTransactionReadOnly(definition.isReadOnly());
			TransactionSynchronizationManager.setCurrentTransactionName(definition.getName());
			TransactionSynchronizationManager.initSynchronization();
		}
	}

都是当前事务相关的信息。

TransactionAspectSupport的prepareTransactionInfo准备事务信息

创建了一个TransactionInfo ，然后把事务管理器，事务注解属性，方法标识符，事务状态设置进去。然后绑定到当前线程私有变量里。

protected TransactionInfo prepareTransactionInfo(@Nullable PlatformTransactionManager tm,
			@Nullable TransactionAttribute txAttr, String joinpointIdentification,
			@Nullable TransactionStatus status) {
		//创建事务信息
		TransactionInfo txInfo = new TransactionInfo(tm, txAttr, joinpointIdentification);
		if (txAttr != null) {
		...
			txInfo.newTransactionStatus(status);//设置新事务状态
		}
		else {
			
			if (logger.isTraceEnabled()) {
				logger.trace("No need to create transaction for [" + joinpointIdentification +
						"]: This method is not transactional.");
			}
		}
		...
		txInfo.bindToThread();//事务信息绑定到当前线程
		return txInfo;
	}

TransactionAspectSupport的completeTransactionAfterThrowing处理异常

如果支持回滚的话就进行回滚，否则就处理提交，提交里面如果TransactionStatus.isRollbackOnly()=true的话也会进行回滚处理。

	protected void completeTransactionAfterThrowing(@Nullable TransactionInfo txInfo, Throwable ex) {
		if (txInfo != null && txInfo.getTransactionStatus() != null) {
			if (logger.isTraceEnabled()) {
				logger.trace("Completing transaction for [" + txInfo.getJoinpointIdentification() +
						"] after exception: " + ex);
			}
			if (txInfo.transactionAttribute != null && txInfo.transactionAttribute.rollbackOn(ex)) {
				try {//进行回滚
					txInfo.getTransactionManager().rollback(txInfo.getTransactionStatus());
				}
				catch (TransactionSystemException ex2) {
					logger.error("Application exception overridden by rollback exception", ex);
					ex2.initApplicationException(ex);
					throw ex2;
				}
				catch (RuntimeException | Error ex2) {
					logger.error("Application exception overridden by rollback exception", ex);
					throw ex2;
				}
			}
			else {

				try {
					txInfo.getTransactionManager().commit(txInfo.getTransactionStatus());
				}
				catch (TransactionSystemException ex2) {
					logger.error("Application exception overridden by commit exception", ex);
					ex2.initApplicationException(ex);
					throw ex2;
				}
				catch (RuntimeException | Error ex2) {
					logger.error("Application exception overridden by commit exception", ex);
					throw ex2;
				}
			}
		}
	}

DelegatingTransactionAttribute的rollbackOn是否可以回滚

回滚对异常是有要求的。

	@Override
	public boolean rollbackOn(Throwable ex) {
		return this.targetAttribute.rollbackOn(ex);
	}

RuleBasedTransactionAttribute的rollbackOn

先处理回滚的规则，就是事务注解里的rollbackFor，rollbackForClassName，noRollbackFor，noRollbackForClassName属性。如果没有设置就会调用父类的rollbackOn。

@Override
	public boolean rollbackOn(Throwable ex) {
		if (logger.isTraceEnabled()) {
			logger.trace("Applying rules to determine whether transaction should rollback on " + ex);
		}

		RollbackRuleAttribute winner = null;
		int deepest = Integer.MAX_VALUE;
		//处理设置的回滚规则
		if (this.rollbackRules != null) {
			for (RollbackRuleAttribute rule : this.rollbackRules) {
				int depth = rule.getDepth(ex);
				if (depth >= 0 && depth < deepest) {
					deepest = depth;
					winner = rule;
				}
			}
		}

		if (logger.isTraceEnabled()) {
			logger.trace("Winning rollback rule is: " + winner);
		}

		// User superclass behavior (rollback on unchecked) if no rule matches.
		if (winner == null) {
			logger.trace("No relevant rollback rule found: applying default rules");
			return super.rollbackOn(ex);
		}

		return !(winner instanceof NoRollbackRuleAttribute);
	}

DefaultTransactionAttribute的rollbackOn

可以看到这里就是的异常，要么是RuntimeException的实例，要么是Error的实例。

	@Override
	public boolean rollbackOn(Throwable ex) {
		return (ex instanceof RuntimeException || ex instanceof Error);
	}

AbstractPlatformTransactionManager的rollback回滚

事务管理器根据事务状态来处理回滚。

	@Override
	public final void rollback(TransactionStatus status) throws TransactionException {
		if (status.isCompleted()) {
			throw new IllegalTransactionStateException(
					"Transaction is already completed - do not call commit or rollback more than once per transaction");
		}

		DefaultTransactionStatus defStatus = (DefaultTransactionStatus) status;
		processRollback(defStatus, false);
	}

关键的就是processRollback，下次讲。

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。