Spring5源码解析4-refresh方法之invokeBeanFactoryPostProcessors

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invokeBeanFactoryPostProcessors(beanFactory);方法源码如下:

protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
	// getBeanFactoryPostProcessors 获取的是 this.beanFactoryPostProcessors;
	//this.beanFactoryPostProcessors 只能通过 AbstractApplicationContext.addBeanFactoryPostProcessor 方法添加
	PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());

	// Detect a LoadTimeWeaver and prepare for weaving, if found in the meantime
	// (e.g. through an @Bean method registered by ConfigurationClassPostProcessor)
	if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
		beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
		beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
	}
}

getBeanFactoryPostProcessors()方法获取的是AbstractApplicationContext#beanFactoryPostProcessors这个成员变量。

这个成员变量只能通过代码中手动编码调用AbstractApplicationContext#addBeanFactoryPostProcessor方法来添加新的元素。很明显,我们这里为空。

invokeBeanFactoryPostProcessors(beanFactory)方法的主要的逻辑在PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors方法中:

//PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors())源码
public static void invokeBeanFactoryPostProcessors(
		ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {

	// Invoke BeanDefinitionRegistryPostProcessors first, if any.
	Set<String> processedBeans = new HashSet<>();

	if (beanFactory instanceof BeanDefinitionRegistry) {
		BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
		List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
		List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();

		//beanFactoryPostProcessors是传进来里的对象,把传入的对象分类放入 BeanFactoryPostProcessor 和  BeanDefinitionRegistryPostProcessor
		//BeanDefinitionRegistryPostProcessor extends BeanFactoryPostProcessor ,是一个特殊的 BeanFactoryPostProcessor
		for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
			if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
				BeanDefinitionRegistryPostProcessor registryProcessor =
						(BeanDefinitionRegistryPostProcessor) postProcessor;
				//如果传入的beanFactoryPostProcessors是它的子类,即:BeanDefinitionRegistryPostProcessor
				//则执行传入的BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry方法
				registryProcessor.postProcessBeanDefinitionRegistry(registry);
				registryProcessors.add(registryProcessor);
			} else {
				regularPostProcessors.add(postProcessor);
			}
		}

		// Do noitialize FactoryBeans here: We need to leave all regular beans
		// uninitialized to let the bean factory post-processors apply to them!
		// Separate between BeanDefinitionRegistryPostProcessors that implement
		// PriorityOrdered, Ordered, and the rest.
		List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();

		// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.

		//这里只能拿到spring内部的BeanDefinitionRegistryPostProcessor,
		//因为到这里spring还没有去扫描Bean,获取不到我们通过@Component标识的自定义BeanDefinitionRegistryPostProcessor
		//一般默认情况下,这里只有一个,BeanName:org.springframework.context.annotation.internalConfigurationAnnotationProcessor
		//对应的BeanClass:ConfigurationClassPostProcessor
		String[] postProcessorNames =
				beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
		for (String ppName : postProcessorNames) {
			if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
				//beanFactory.getBean, 这里开始创建BeanDefinitionRegistryPostProcessor bean 了
				currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
				processedBeans.add(ppName);
			}
		}

		//排序
		sortPostProcessors(currentRegistryProcessors, beanFactory);

		// registryProcessors 中放的是 BeanDefinitionRegistryPostProcessor
		// 因为这里只执行eanDefinitionRegistryPostProcessor中独有的方法,而不会执行其父类即BeanFactoryProcessor的方法
		// 所以这里需要把处理器放入一个集合中,后续统一执行父类的方法
		registryProcessors.addAll(currentRegistryProcessors);

		// 执行BeanDefinitionRegistryPostProcessor,currentRegistryProcessors中放的是spring内部的BeanDefinitionRegistryPostProcessor
		// 默认情况下,只有 org.springframework.context.annotation.ConfigurationClassPostProcessor
		// ConfigurationClassPostProcessor 里面就是在执行扫描Bean,并且注册BeanDefinition
		invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);

		// 清空这个临时变量,方便后面再使用
		currentRegistryProcessors.clear();

		// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
		// 这里已经可以获取到我们通过注册到Spring容器的 BeanDefinitionRegistryPostProcessor 了
		postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
		for (String ppName : postProcessorNames) {
			// 之前优先处理的是实现PriorityOrdered接口的,而PriorityOrdered接口也实现了Ordered接口
			// 所有这里需要把之前已经处理过的给过滤掉
			if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
				//之前这个临时变量已经被清空了,现在又开始放东西了
				currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
				processedBeans.add(ppName);
			}
		}

		//排序
		sortPostProcessors(currentRegistryProcessors, beanFactory);

		registryProcessors.addAll(currentRegistryProcessors);

		// 执行BeanDefinitionRegistryPostProcessor
		invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);

		//清空临时变量
		currentRegistryProcessors.clear();

		// Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
		boolean reiterate = true;
		while (reiterate) {
			reiterate = false;
			postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
			for (String ppName : postProcessorNames) {
				//执行没有实现Ordered接口的BeanDefinitionRegistryPostProcessor
				if (!processedBeans.contains(ppName)) {
					currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
					processedBeans.add(ppName);
					reiterate = true;
				}
			}
			sortPostProcessors(currentRegistryProcessors, beanFactory);
			registryProcessors.addAll(currentRegistryProcessors);
			invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
			currentRegistryProcessors.clear();
		}

		// Now, invoke the postProcessBeanFactory callback of all processors handled so far.
		// List<BeanDefinitionRegistryPostProcessor> registryProcessors
		// 之前已经执行过BeanDefinitionRegistryPostProcessor独有方法,现在执行其父类方法
		invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);

		// List<BeanFactoryPostProcessor> regularPostProcessors
		// 执行 BeanFactoryPostProcessor 方法
		invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
	} else {
		// Invoke factory processors registered with the context instance.
		invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
	}

	// Do not initialize FactoryBeans here: We need to leave all regular beans
	// uninitialized to let the bean factory post-processors apply to them!
	// 获取 BeanFactoryPostProcessor 的 beanName
	String[] postProcessorNames =
			beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

	// Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
	// Ordered, and the rest.
	List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
	List<String> orderedPostProcessorNames = new ArrayList<>();
	List<String> nonOrderedPostProcessorNames = new ArrayList<>();
	for (String ppName : postProcessorNames) {
		// 如果已经被执行过了,就不在执行
		// 因为一开始先获取的BeanDefinitionRegistryPostProcessor,而BeanDefinitionRegistryPostProcessor继承了BeanFactoryPostProcessor
		if (processedBeans.contains(ppName)) {
			// skip - already processed in first phase above
		} else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
			priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
		} else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
			orderedPostProcessorNames.add(ppName);
		} else {
			nonOrderedPostProcessorNames.add(ppName);
		}
	}

	// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
	// 根据不同的优先级,按序执行 BeanFactoryPostProcessor
	sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
	invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

	// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
	List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>();
	for (String postProcessorName : orderedPostProcessorNames) {
		orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
	}
	sortPostProcessors(orderedPostProcessors, beanFactory);
	invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);

	// Finally, invoke all other BeanFactoryPostProcessors.
	List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>();
	for (String postProcessorName : nonOrderedPostProcessorNames) {
		nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
	}
	invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);

	// Clear cached merged bean definitions since the post-processors might have
	// modified the original metadata, e.g. replacing placeholders in values...
	beanFactory.clearMetadataCache();
}

源码超级长,我们慢慢来看。

  1. Spring容器使用的BeanFactoryDefaultListableBeanFactory,它实现了BeanDefinitionRegistry接口,if条件成立。

  2. 优先处理程序传进来的beanFactoryPostProcessors,也就是我们手动调用AbstractApplicationContext#addBeanFactoryPostProcessor方法来添加的BeanFactoryPostProcessor

  3. BeanFactoryPostProcessor是一个顶级接口,他还有一个子类BeanDefinitionRegistryPostProcessor。在该方法中声明了两个List来存放BeanFactoryPostProcessorBeanDefinitionRegistryPostProcessor,以便控制这两个接口方法的执行。

  4. 遍历传入的List<BeanFactoryPostProcessor> beanFactoryPostProcessors,将其分类放到两个List中。如果传入的是BeanDefinitionRegistryPostProcessor类,则先执行BeanDefinitionRegistryPostProcessor类中独有的方法postProcessBeanDefinitionRegistry方法。当然,我们这里传入的List<BeanFactoryPostProcessor> beanFactoryPostProcessors为空。

  5. 第一次执行beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);方法,从容器中获取BeanDefinitionRegistryPostProcessor类型的Bean的name(这里只是获取名称,还没有实例化Bean)。注意,程序执行到这里,Spring还没有扫描包,还没有将项目中的Bean注册到容器中。默认情况下,这里返回的数据为如下图所示。回忆一下,这个BeanDefinition是在什么时候被加入到BeanFactory的呢?是在AnnotationConfigApplicationContext的无参构造器中创建reader时注册的BeanDefinition。其中BeanName为org.springframework.context.annotation.internalConfigurationAnnotationProcessor,对应的Class为org.springframework.context.annotation.ConfigurationClassPostProcessor

    image.png

  6. 遍历这个获取的postProcessorNames,如果实现了PriorityOrdered接口,就调用beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class)方法,从容器中获取这个Bean,将其加入到临时变量List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors中。

  7. currentRegistryProcessors中的元素进行排序,然后执行BeanDefinitionRegistryPostProcessor中的特有方法postProcessBeanDefinitionRegistry。注意哦,这里没有执行其父类的方法,而是又将其放到List<BeanDefinitionRegistryPostProcessor> registryProcessors中,到后面再执行其父类方法。

  8. 默认情况下,此时currentRegistryProcessors中只有一个Bean即:org.springframework.context.annotation.ConfigurationClassPostProcessor(它实现了PriorityOrdered接口)。ConfigurationClassPostProcessor是一个非常重要的类,我们后面在讲。当程序执行完ConfigurationClassPostProcessorBeanDefinitionRegistryPostProcessor方法后,我们程序中的Bean就被注册到了Spring容器中了,需要注意的是,这里还只是注册了BeanDefinition,还没有创建Bean对象。

    currentRegistryProcessors

    ((DefaultListableBeanFactory) registry).beanDefinitionMap

  9. 当第二次执行postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);方法,此时因为之前已经完成了Bean的扫描,所以如果我们有自定义的BeanDefinitionRegistryPostProcessor就可以在这里被获取了。获取之前,判断其是否实现Ordered接口,并且之前没有被执行过,则调用getBean方法,从容器中获取该Bean,然后进行排序,执行postProcessBeanDefinitionRegistry方法。

  10. 前面已经按顺序执行了实现PriorityOrderedOrdered接口的BeanDefinitionRegistryPostProcessor,最后,执行没有实现Ordered接口的BeanDefinitionRegistryPostProcessorpostProcessBeanDefinitionRegistry方法。执行完之后再BeanDefinitionRegistryPostProcessor的父类方法postProcessBeanFactory

  11. 获取容器中还没有被执行过的实现BeanFactoryPostProcessor接口的Bean,然后按顺序执行的postProcessBeanFactory。默认情况下,这里会获取到:

postProcessorNames

由于Bean org.springframework.context.annotation.internalConfigurationAnnotationProcessor(对应的Class为org.springframework.context.annotation.ConfigurationClassPostProcessor)在之前已经被执行了,这里只会执行Bean org.springframework.context.event.internalEventListenerProcessor(对应的Class为org.springframework.context.event.EventListenerMethodProcessor)的postProcessBeanFactory方法,源码如下:

//org.springframework.context.event.EventListenerMethodProcessor#postProcessBeanFactory 源码
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
	this.beanFactory = beanFactory;

	Map<String, EventListenerFactory> beans = beanFactory.getBeansOfType(EventListenerFactory.class, false, false);
	List<EventListenerFactory> factories = new ArrayList<>(beans.values());
	AnnotationAwareOrderComparator.sort(factories);
	this.eventListenerFactories = factories;
}

未完待续......

源码学习笔记:github.com/shenjianeng…

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