Spring源码解析

办公设备租赁，深圳惠源.

文章目录

• Spring源码解析
• 前言
• 一、EnableTransactionManagement
• • 1、EnableTransactionManagement
  • 2、TransactionManagementConfigurationSelector
  • 3、AutoProxyRegistrar
  • • 3.1 registerAutoProxyCreatorIfNecessary-往容器加InfrastructureAdvisorAutoProxyCreator的Bean定义
    • 3.2、InfrastructureAdvisorAutoProxyCreator继承结构
    • 4、ProxyTransactionManagementConfiguration
• 二、怎么进入InfrastructureAdvisorAutoProxyCreator入口，生成代理对象
• • 1.注册BeanPostProcessors到Bean工厂
  • 2、 BeanPostProcessors的执行
• 总结

前言

该部分需要了解Spring事务的基本概念-切面
SpringBoot以@EnableTransactionManagement注解启动事务管理，所以我们从EnableTransactionManagement开始分析。

一、EnableTransactionManagement

1、EnableTransactionManagement

如下可以看到EnableTransactionManagement引入了注解@Import，Import的作用可以看下SpringBoot源码解析二，可以添加Bean定义，接下来看下TransactionManagementConfigurationSelector

2、TransactionManagementConfigurationSelector

默认代理有JDK代理和ASPETJ两种方式，我们分析JDK代理
JDK代理引入了AutoProxyRegistrar和ProxyTransactionManagementConfiguration

3、AutoProxyRegistrar

3.1 registerAutoProxyCreatorIfNecessary-往容器加InfrastructureAdvisorAutoProxyCreator的Bean定义

private static BeanDefinition registerOrEscalateApcAsRequired(
			Class<?> cls, BeanDefinitionRegistry registry, @Nullable Object source) {

		Assert.notNull(registry, "BeanDefinitionRegistry must not be null");

		if (registry.containsBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME)) {
			BeanDefinition apcDefinition = registry.getBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME);
			if (!cls.getName().equals(apcDefinition.getBeanClassName())) {
				int currentPriority = findPriorityForClass(apcDefinition.getBeanClassName());
				int requiredPriority = findPriorityForClass(cls);
				if (currentPriority < requiredPriority) {
					apcDefinition.setBeanClassName(cls.getName());
				}
			}
			return null;
		}

		RootBeanDefinition beanDefinition = new RootBeanDefinition(cls);
		beanDefinition.setSource(source);
		beanDefinition.getPropertyValues().add("order", Ordered.HIGHEST_PRECEDENCE);
		beanDefinition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
		registry.registerBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME, beanDefinition);
		return beanDefinition;
	}

3.2、InfrastructureAdvisorAutoProxyCreator继承结构

分析InfrastructureAdvisorAutoProxyCreator的继承结构，发现其父类有实现BeanPostProcessor（这一点很重要，从这里入口对Bean进行代理而实现事务）

4、ProxyTransactionManagementConfiguration

从类名可以看出是事务配置类，为事务注入切面BeanFactoryTransactionAttributeSourceAdvisor，事务切面包含了TransactionInterceptor事务处理器拦截器，事务在该类处理

// 切面BeanFactoryTransactionAttributeSourceAdvisor
@Bean(name = TransactionManagementConfigUtils.TRANSACTION_ADVISOR_BEAN_NAME)
	@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
	public BeanFactoryTransactionAttributeSourceAdvisor transactionAdvisor(
			TransactionAttributeSource transactionAttributeSource,
			TransactionInterceptor transactionInterceptor) {
		BeanFactoryTransactionAttributeSourceAdvisor advisor = new BeanFactoryTransactionAttributeSourceAdvisor();
		advisor.setTransactionAttributeSource(transactionAttributeSource);
		advisor.setAdvice(transactionInterceptor);
		if (this.enableTx != null) {
			advisor.setOrder(this.enableTx.<Integer>getNumber("order"));
		}
		return advisor;
	}

	@Bean
	@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
	public TransactionAttributeSource transactionAttributeSource() {
		return new AnnotationTransactionAttributeSource();
	}

	@Bean
	@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
	public TransactionInterceptor transactionInterceptor(
			TransactionAttributeSource transactionAttributeSource) {
		TransactionInterceptor interceptor = new TransactionInterceptor();
		interceptor.setTransactionAttributeSource(transactionAttributeSource);
		if (this.txManager != null) {
			interceptor.setTransactionManager(this.txManager);
		}
		return interceptor;
	}

>

第一阶段小总结：EnableTransactionManagement为我们准备好了事务，生成事务代理对象的入口-InfrastructureAdvisorAutoProxyCreator，事务切面-BeanFactoryTransactionAttributeSourceAdvisor

二、怎么进入InfrastructureAdvisorAutoProxyCreator入口，生成代理对象

上节分析了invokeBeanFactoryPostProcessors-执行实现了postProcessBeanFactory的类的postProcessBeanFactory方法，这节继续分析registerBeanPostProcessors-将BeanPostProcessors注入到Bean工厂

1.注册BeanPostProcessors到Bean工厂

public static void registerBeanPostProcessors(
			ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {

        // 获取所有实现了BeanPostProcessor的Bean的名称
		String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);


		int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
		beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

		// 获取所有继承了PriorityOrdered的BeanPostProcessors 
		// 排序
		List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
		List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
		List<String> orderedPostProcessorNames = new ArrayList<>();
		List<String> nonOrderedPostProcessorNames = new ArrayList<>();
		for (String ppName : postProcessorNames) {
			if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
				BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
				priorityOrderedPostProcessors.add(pp);
				if (pp instanceof MergedBeanDefinitionPostProcessor) {
					internalPostProcessors.add(pp);
				}
			}
			else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
				orderedPostProcessorNames.add(ppName);
			}
			else {
				nonOrderedPostProcessorNames.add(ppName);
			}
		}

		// 第一, 注册实现了PriorityOrdered的BeanPostProcessors
		sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
		registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

		// 接下来, 注册实现了Ordered的BeanPostProcessors
		List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
		for (String ppName : orderedPostProcessorNames) {
			BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
			orderedPostProcessors.add(pp);
			if (pp instanceof MergedBeanDefinitionPostProcessor) {
				internalPostProcessors.add(pp);
			}
		}
		sortPostProcessors(orderedPostProcessors, beanFactory);
		registerBeanPostProcessors(beanFactory, orderedPostProcessors);

		// 然后, 注册剩余的常规的BeanPostProcessors.
		List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
		for (String ppName : nonOrderedPostProcessorNames) {
			BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
			nonOrderedPostProcessors.add(pp);
			if (pp instanceof MergedBeanDefinitionPostProcessor) {
				internalPostProcessors.add(pp);
			}
		}
		registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);

		// Finally, re-register all internal BeanPostProcessors.
		sortPostProcessors(internalPostProcessors, beanFactory);
		registerBeanPostProcessors(beanFactory, internalPostProcessors);

		// Re-register post-processor for detecting inner beans as ApplicationListeners,
		// moving it to the end of the processor chain (for picking up proxies etc).
		beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
	}

2、 BeanPostProcessors的执行

Spring在getBean的时候会去执行BeanPostProcessors的方法，getBean后续分析，我们直接进入执行BeanPostProcessors

/**
	 * 创建Bean实例
	 * @see #doCreateBean
	 */
	@Override
	protected Object createBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
			throws BeanCreationException {

		try {
			// 给BeanPostProcessors一个机会去返回代理对象，就是这里啦
			Object bean = resolveBeforeInstantiation(beanName, mbdToUse);
			if (bean != null) {
				return bean;
			}
		}
		catch (Throwable ex) {
			throw new BeanCreationException(mbdToUse.getResourceDescription(), beanName,
					"BeanPostProcessor before instantiation of bean failed", ex);
		}

		try {
			Object beanInstance = doCreateBean(beanName, mbdToUse, args);
			if (logger.isTraceEnabled()) {
				logger.trace("Finished creating instance of bean '" + beanName + "'");
			}
			return beanInstance;
		}
		catch (BeanCreationException | ImplicitlyAppearedSingletonException ex) {
			// A previously detected exception with proper bean creation context already,
			// or illegal singleton state to be communicated up to DefaultSingletonBeanRegistry.
			throw ex;
		}
		catch (Throwable ex) {
			throw new BeanCreationException(
					mbdToUse.getResourceDescription(), beanName, "Unexpected exception during bean creation", ex);
		}
	}

3、执行InfrastructureAdvisorAutoProxyCreator的postProcessBeforeInstantiation()方法

protected Object resolveBeforeInstantiation(String beanName, RootBeanDefinition mbd) {
		Object bean = null;
		if (!Boolean.FALSE.equals(mbd.beforeInstantiationResolved)) {
			// Make sure bean class is actually resolved at this point.
			if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
				Class<?> targetType = determineTargetType(beanName, mbd);
				if (targetType != null) {
					bean = applyBeanPostProcessorsBeforeInstantiation(targetType, beanName);
					if (bean != null) {
						bean = applyBeanPostProcessorsAfterInitialization(bean, beanName);
					}
				}
			}
			mbd.beforeInstantiationResolved = (bean != null);
		}
		return bean;
	}

// 
protected Object applyBeanPostProcessorsBeforeInstantiation(Class<?> beanClass, String beanName) {
		for (BeanPostProcessor bp : getBeanPostProcessors()) {
			if (bp instanceof InstantiationAwareBeanPostProcessor) {
				InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
				Object result = ibp.postProcessBeforeInstantiation(beanClass, beanName);
				if (result != null) {
					return result;
				}
			}
		}
		return null;
	}

4、创建代理对象
JDK代理JdkDynamicAopProxy
Cglib代理为CglibAopProxy

public Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) {
		Object cacheKey = getCacheKey(beanClass, beanName);
		// 判断是否需要创建代理对象
		if (!StringUtils.hasLength(beanName) || !this.targetSourcedBeans.contains(beanName)) {
			if (this.advisedBeans.containsKey(cacheKey)) {
				return null;
			}
			if (isInfrastructureClass(beanClass) || shouldSkip(beanClass, beanName)) {
				this.advisedBeans.put(cacheKey, Boolean.FALSE);
				return null;
			}
		}

		TargetSource targetSource = getCustomTargetSource(beanClass, beanName);
		if (targetSource != null) {
			if (StringUtils.hasLength(beanName)) {
				this.targetSourcedBeans.add(beanName);
			}
			Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(beanClass, beanName, targetSource);
			Object proxy = createProxy(beanClass, beanName, specificInterceptors, targetSource);
			this.proxyTypes.put(cacheKey, proxy.getClass());
			return proxy;
		}

		return null;
	}

总结

以上就是Spring事务代理对象的创建过程