SpringIOC源码阅读笔记（10）

分析完BeanFactory容器的加载，接下来看一下更复杂的容器ApplicationContext的加载，这个容器也是我们目前使用比较多的容器。跟BeanFactory比起来，ApplicationContext有如下区别：
1.继承 MessageSource，提供国际化的标准访问策略。
2.继承 ApplicationEventPublisher ，提供强大的事件机制。
3.扩展 ResourceLoader，可以用来加载多个 Resource，可以灵活访问不同的资源。
4.对 Web 应用的支持。
同样的可以从一行代码开始分析：
ApplicationContext bs = new ClassPathXmlApplicationContext(“beanFactoryTest.xml”);
看看Applicationcontext的UML图：

以及ClassPathXmlApplicationContext
首先是ClassPathXmlApplicationContext的构造函数：

	public ClassPathXmlApplicationContext(String configLocation) throws BeansException {
	//支持多个配置文件已数组方式同时传入
		this(new String[] {configLocation}, true, null);
	}
	public ClassPathXmlApplicationContext(
			String[] configLocations, boolean refresh, @Nullable ApplicationContext parent)
			throws BeansException {
		//(1)设置父类
		super(parent);
		//(2)设置配置文件地址
		setConfigLocations(configLocations);
		//(3)刷新
		if (refresh) {
			refresh();
		}
	}

(1)super(parent);实现是在AbstractApplicationContext，有属性private ApplicationContext parent;
(2)setConfigLocations(configLocations);实现是在AbstractRefreshableConfigApplicationContext：

public void setConfigLocations(@Nullable String... locations) {
		if (locations != null) {
			Assert.noNullElements(locations, "Config locations must not be null");
			this.configLocations = new String[locations.length];
			//将参数一个个设置进成员变量private String[] configLocations;
			for (int i = 0; i < locations.length; i++) {
			//如果含有特殊字符例如${var}，resolvePath会搜索匹配的系统变量并且替换
				this.configLocations[i] = resolvePath(locations[i]).trim();
			}
		}
		else {
			this.configLocations = null;
		}
	}

（3）refresh() 实现是在AbstractApplicationContext

@Override
	public void refresh() throws BeansException, IllegalStateException {
		synchronized (this.startupShutdownMonitor) {
			// Prepare this context for refreshing.
			//准备刷新的上下文环境
			prepareRefresh();

			// Tell the subclass to refresh the internal bean factory.
			//初始化BeanFactory，并且进行XML文件读取
			ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

			// Prepare the bean factory for use in this context.
			//对beanFactory进行各种功能填充
			prepareBeanFactory(beanFactory);

			try {
				// Allows post-processing of the bean factory in context subclasses.
				//子类覆盖方法做额外的处理
				postProcessBeanFactory(beanFactory);

				// Invoke factory processors registered as beans in the context.
				//激活各种BeanFactory处理器
				invokeBeanFactoryPostProcessors(beanFactory);

				// Register bean processors that intercept bean creation.
				//注册Bean处理器
				registerBeanPostProcessors(beanFactory);

				// Initialize message source for this context.
				//初始化Message源
				initMessageSource();

				// Initialize event multicaster for this context.
				//初始化应用消息广播器
				initApplicationEventMulticaster();

				// Initialize other special beans in specific context subclasses.
				//留给子类初始化其他的Bean
				onRefresh();

				// Check for listener beans and register them.
				//注册监听器
				registerListeners();

				// Instantiate all remaining (non-lazy-init) singletons.
				//初始化剩下的单例（非惰性）
				finishBeanFactoryInitialization(beanFactory);

				// Last step: publish corresponding event.
				//完成刷新过程
				finishRefresh();
			}

			catch (BeansException ex) {
				if (logger.isWarnEnabled()) {
					logger.warn("Exception encountered during context initialization - " +
							"cancelling refresh attempt: " + ex);
				}

				// Destroy already created singletons to avoid dangling resources.
				destroyBeans();

				// Reset 'active' flag.
				cancelRefresh(ex);

				// Propagate exception to caller.
				throw ex;
			}

			finally {
				// Reset common introspection caches in Spring's core, since we
				// might not ever need metadata for singleton beans anymore...
				resetCommonCaches();
			}
		}
	}

在刷新这个环节做了很多事情，下面一个个分析以上的方法：
1.环境准备prepareRefresh();

protected void prepareRefresh() {
//开始时间
		this.startupDate = System.currentTimeMillis();
		//没有关闭
		this.closed.set(false);
		//活跃状态
		this.active.set(true);

		if (logger.isInfoEnabled()) {
			logger.info("Refreshing " + this);
		}

		// Initialize any placeholder property sources in the context environment
		//空实现，留给子类覆盖
		initPropertySources();

		// Validate that all properties marked as required are resolvable
		// see ConfigurablePropertyResolver#setRequiredProperties
		//对属性进行必要的验证
		getEnvironment().validateRequiredProperties();

		// Allow for the collection of early ApplicationEvents,
		// to be published once the multicaster is available...
		this.earlyApplicationEvents = new LinkedHashSet<>();
	}

2.加载BeanFactory，实现在AbstractApplicationContext

	protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
	//初始化BeanFactory，并且从xml中读取信息
		refreshBeanFactory();
		//获取BeanFactory
		ConfigurableListableBeanFactory beanFactory = getBeanFactory();
		if (logger.isDebugEnabled()) {
			logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
		}
		return beanFactory;
	}

refreshBeanFactory，方法实现在AbstractRefreshableApplicationContext

	@Override
	protected final void refreshBeanFactory() throws BeansException {
	//如果已经有BeanFactory，就摧毁beans并且关闭BeanFactory
		if (hasBeanFactory()) {
			destroyBeans();
			closeBeanFactory();
		}
		try {
			//创建DefaultListableBeanFactory
			DefaultListableBeanFactory beanFactory = createBeanFactory();
			//序列化指定的id
			beanFactory.setSerializationId(getId());
			//定制BeanFactory
			customizeBeanFactory(beanFactory);
			//初始化DocumentReader，进行XML文件读取及解析
			loadBeanDefinitions(beanFactory);
			//绑定成员变量
			synchronized (this.beanFactoryMonitor) {
				this.beanFactory = beanFactory;
			}
		}
		catch (IOException ex) {
			throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
		}
	}

//将所有实例化的bean销毁
protected void destroyBeans() {
		getBeanFactory().destroySingletons();
	}
	@Override
	public void destroySingletons() {
		super.destroySingletons();
		//1.删去DefaultListableBeanFactory中manualSingletonNames
		this.manualSingletonNames.clear();
		//删去allBeanNamesByType和singletonBeanNamesByType
		clearByTypeCache();
	}
		@Override
	public void destroySingletons() {
		super.destroySingletons();
		//删去FactoryBeanRegistrySupport中的factoryBeanObjectCache
		this.factoryBeanObjectCache.clear();
	}
	//最后清空DefaultSingletonBeanRegistry中的map
		public void destroySingletons() {
		if (logger.isDebugEnabled()) {
			logger.debug("Destroying singletons in " + this);
		}
		synchronized (this.singletonObjects) {
			this.singletonsCurrentlyInDestruction = true;
		}

		String[] disposableBeanNames;
		synchronized (this.disposableBeans) {
			disposableBeanNames = StringUtils.toStringArray(this.disposableBeans.keySet());
		}
		for (int i = disposableBeanNames.length - 1; i >= 0; i--) {
			destroySingleton(disposableBeanNames[i]);
		}

		this.containedBeanMap.clear();
		this.dependentBeanMap.clear();
		this.dependenciesForBeanMap.clear();

		synchronized (this.singletonObjects) {
			this.singletonObjects.clear();
			this.singletonFactories.clear();
			this.earlySingletonObjects.clear();
			this.registeredSingletons.clear();
			this.singletonsCurrentlyInDestruction = false;
		}
	}

@Override
//如果在AbstractRefreshableApplicationContext有绑定的beanFactory，就解除绑定。
	protected final void closeBeanFactory() {
		synchronized (this.beanFactoryMonitor) {
			if (this.beanFactory != null) {
				this.beanFactory.setSerializationId(null);
				this.beanFactory = null;
			}
		}
	}

创建BeanFactory

	protected DefaultListableBeanFactory createBeanFactory() {
		return new DefaultListableBeanFactory(getInternalParentBeanFactory());
	}

指定id，将applicationContext的id指定给BeanFactory的serializationId

	public void setSerializationId(@Nullable String serializationId) {
		if (serializationId != null) {
			serializableFactories.put(serializationId, new WeakReference<>(this));
		}
		else if (this.serializationId != null) {
			serializableFactories.remove(this.serializationId);
		}
		this.serializationId = serializationId;
	}

定制BeanFactory，增加了是否允许覆盖是否允许扩展

	protected void customizeBeanFactory(DefaultListableBeanFactory beanFactory) {
		if (this.allowBeanDefinitionOverriding != null) {
			beanFactory.setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);
		}
		if (this.allowCircularReferences != null) {
			beanFactory.setAllowCircularReferences(this.allowCircularReferences);
		}
	}

加载BeanDefinition，实现在AbstractXmlApplicationContext

	protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
		// Create a new XmlBeanDefinitionReader for the given BeanFactory.‘’
		//给指定的BeanFactory创建XmlBeanDefinitionReader
		XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);

		// Configure the bean definition reader with this context's
		// resource loading environment.
		//进行环境变量的设置
		beanDefinitionReader.setEnvironment(this.getEnvironment());
		beanDefinitionReader.setResourceLoader(this);
		beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));

		// Allow a subclass to provide custom initialization of the reader,
		// then proceed with actually loading the bean definitions.
		//进行设置
		initBeanDefinitionReader(beanDefinitionReader);
		loadBeanDefinitions(beanDefinitionReader);
	}

	protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {
	//得到xml资源
		Resource[] configResources = getConfigResources();
		if (configResources != null) {
			reader.loadBeanDefinitions(configResources);
		}
		//得到xml地址
		String[] configLocations = getConfigLocations();
		if (configLocations != null) {
			reader.loadBeanDefinitions(configLocations);
		}
	}

3.功能扩展
接下来进入prepareBeanFactory

protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
		// Tell the internal bean factory to use the context's class loader etc.
		//将beanFactory的classLoader设置成当前context的classLoader
		beanFactory.setBeanClassLoader(getClassLoader());
		//增加SPEL解析器，这个是在调用AbstractAutowireCapableBeanFactory类的applyPropertyValues来完成功能，使用的是beanExpressionResolver的evaluate
		beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
		//增加propertyEditor
		beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));

		// Configure the bean factory with context callbacks.
		//添加ApplicationContextAwareProcessor
		beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
		//忽略几个自动装配接口
		beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
		beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
		beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
		beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
		beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
		beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);

		// BeanFactory interface not registered as resolvable type in a plain factory.
		// MessageSource registered (and found for autowiring) as a bean.
		//设置自动装配的特殊规则
		beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
		beanFactory.registerResolvableDependency(ResourceLoader.class, this);
		beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
		beanFactory.registerResolvableDependency(ApplicationContext.class, this);

		// Register early post-processor for detecting inner beans as ApplicationListeners.
		//添加检测内部beans的后处理器
		beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));

		// Detect a LoadTimeWeaver and prepare for weaving, if found.
		// 增加对AspectJ的支持
		if (beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
			beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
			// Set a temporary ClassLoader for type matching.
			beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
		}

		// Register default environment beans.
		//添加默认的系统变量bean
		if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) {
			beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
		}
		if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) {
			beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());
		}
		if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) {
			beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());
		}
	}

添加属性注册编辑器
这个步骤的根源得追溯到initBeanWrapper方法，这时候会调用ResourceEditorRegistrar的registerCustomEditors。

	protected void initBeanWrapper(BeanWrapper bw) {
		bw.setConversionService(getConversionService());
		registerCustomEditors(bw);
	}

//beanWrapper继承PropertyEditorRegistry，所以它也是一个registry
protected void registerCustomEditors(PropertyEditorRegistry registry) {
		PropertyEditorRegistrySupport registrySupport =
				(registry instanceof PropertyEditorRegistrySupport ? (PropertyEditorRegistrySupport) registry : null);
		if (registrySupport != null) {
			registrySupport.useConfigValueEditors();
		}
		if (!this.propertyEditorRegistrars.isEmpty()) {
		//遍历在AbstractBeanFactory注册的propertyEditorRegistrars中的PropertyEditorRegistrar，逐个调用registrar.registerCustomEditors(registry)方法
			for (PropertyEditorRegistrar registrar : this.propertyEditorRegistrars) {
				try {
					registrar.registerCustomEditors(registry);
				}
				catch (BeanCreationException ex) {
					Throwable rootCause = ex.getMostSpecificCause();
					if (rootCause instanceof BeanCurrentlyInCreationException) {
						BeanCreationException bce = (BeanCreationException) rootCause;
						String bceBeanName = bce.getBeanName();
						if (bceBeanName != null && isCurrentlyInCreation(bceBeanName)) {
							if (logger.isDebugEnabled()) {
								logger.debug("PropertyEditorRegistrar [" + registrar.getClass().getName() +
										"] failed because it tried to obtain currently created bean '" +
										ex.getBeanName() + "': " + ex.getMessage());
							}
							onSuppressedException(ex);
							continue;
						}
					}
					throw ex;
				}
			}
		}
		if (!this.customEditors.isEmpty()) {
			this.customEditors.forEach((requiredType, editorClass) ->
					registry.registerCustomEditor(requiredType, BeanUtils.instantiateClass(editorClass)));
		}
	}

接下来我们需要知道AbstractBeanFactory中的propertyEditorRegistrars是哪来的。其实就是我们最关注的那行代码：
beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));

	@Override
	public void addPropertyEditorRegistrar(PropertyEditorRegistrar registrar) {
		Assert.notNull(registrar, "PropertyEditorRegistrar must not be null");
		//将ResourceEditorRegistrar加入了propertyEditorRegistrars
		this.propertyEditorRegistrars.add(registrar);
	}

调用了ResourceEditorRegistrar的registerCustomEditors

@Override
	public void registerCustomEditors(PropertyEditorRegistry registry) {
		ResourceEditor baseEditor = new ResourceEditor(this.resourceLoader, this.propertyResolver);
		doRegisterEditor(registry, Resource.class, baseEditor);
		doRegisterEditor(registry, ContextResource.class, baseEditor);
		doRegisterEditor(registry, InputStream.class, new InputStreamEditor(baseEditor));
		doRegisterEditor(registry, InputSource.class, new InputSourceEditor(baseEditor));
		doRegisterEditor(registry, File.class, new FileEditor(baseEditor));
		doRegisterEditor(registry, Path.class, new PathEditor(baseEditor));
		doRegisterEditor(registry, Reader.class, new ReaderEditor(baseEditor));
		doRegisterEditor(registry, URL.class, new URLEditor(baseEditor));

		ClassLoader classLoader = this.resourceLoader.getClassLoader();
		doRegisterEditor(registry, URI.class, new URIEditor(classLoader));
		doRegisterEditor(registry, Class.class, new ClassEditor(classLoader));
		doRegisterEditor(registry, Class[].class, new ClassArrayEditor(classLoader));

		if (this.resourceLoader instanceof ResourcePatternResolver) {
			doRegisterEditor(registry, Resource[].class,
					new ResourceArrayPropertyEditor((ResourcePatternResolver) this.resourceLoader, this.propertyResolver));
		}
	}

逐个调用doRegisterEditor

	private void doRegisterEditor(PropertyEditorRegistry registry, Class<?> requiredType, PropertyEditor editor) {
		if (registry instanceof PropertyEditorRegistrySupport) {
			((PropertyEditorRegistrySupport) registry).overrideDefaultEditor(requiredType, editor);
		}
		else {
			registry.registerCustomEditor(requiredType, editor);
		}
	}

	@Override
	public void registerCustomEditor(Class<?> requiredType, PropertyEditor propertyEditor) {
		registerCustomEditor(requiredType, null, propertyEditor);
	}

	@Override
	public void registerCustomEditor(@Nullable Class<?> requiredType, @Nullable String propertyPath, PropertyEditor propertyEditor) {
		if (requiredType == null && propertyPath == null) {
			throw new IllegalArgumentException("Either requiredType or propertyPath is required");
		}
		if (propertyPath != null) {
			if (this.customEditorsForPath == null) {
				this.customEditorsForPath = new LinkedHashMap<>(16);
			}
			this.customEditorsForPath.put(propertyPath, new CustomEditorHolder(propertyEditor, requiredType));
		}
		else {
			if (this.customEditors == null) {
				this.customEditors = new LinkedHashMap<>(16);
			}
			//最后面追踪到会把这个类型和对应的解析器放到PropertyEditorRegistrySupport的customEditors的map中
			this.customEditors.put(requiredType, propertyEditor);
			this.customEditorCache = null;
		}
	}

ok，属性编辑器就解析完毕了，当输入的数值需要解析时会找到对应的解析器。
接下来是beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
后处理器比较熟悉，主要了解下ApplicationContextAwareProcessor这个处理器，其中后置处理没有实现，看看前置处理：

public Object postProcessBeforeInitialization(final Object bean, String beanName) throws BeansException {
		AccessControlContext acc = null;

		if (System.getSecurityManager() != null &&
				(bean instanceof EnvironmentAware || bean instanceof EmbeddedValueResolverAware ||
						bean instanceof ResourceLoaderAware || bean instanceof ApplicationEventPublisherAware ||
						bean instanceof MessageSourceAware || bean instanceof ApplicationContextAware)) {
			acc = this.applicationContext.getBeanFactory().getAccessControlContext();
		}

		if (acc != null) {
			AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
				invokeAwareInterfaces(bean);
				return null;
			}, acc);
		}
		else {
			invokeAwareInterfaces(bean);
		}

		return bean;
	}

//spring为了实现了以下接口的bean在初始化后提供了对应注入
private void invokeAwareInterfaces(Object bean) {
		if (bean instanceof Aware) {
			if (bean instanceof EnvironmentAware) {
				((EnvironmentAware) bean).setEnvironment(this.applicationContext.getEnvironment());
			}
			if (bean instanceof EmbeddedValueResolverAware) {
				((EmbeddedValueResolverAware) bean).setEmbeddedValueResolver(this.embeddedValueResolver);
			}
			if (bean instanceof ResourceLoaderAware) {
				((ResourceLoaderAware) bean).setResourceLoader(this.applicationContext);
			}
			if (bean instanceof ApplicationEventPublisherAware) {
				((ApplicationEventPublisherAware) bean).setApplicationEventPublisher(this.applicationContext);
			}
			if (bean instanceof MessageSourceAware) {
				((MessageSourceAware) bean).setMessageSource(this.applicationContext);
			}
			if (bean instanceof ApplicationContextAware) {
				((ApplicationContextAware) bean).setApplicationContext(this.applicationContext);
			}
		}
	}

所以就有了下一步忽略对应的接口。而后也必不可少的会有注册以来的功能。

4.激活各种BeanFactory处理器，注意是激活。

protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
		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()));
		}
	}

下面会涉及两种BeanFactoryPostProcessor，BeanFactoryPostProcessor和BeanDefinitionRegistryPostProcessor，BeanDefinitionRegistryPostProcessor extends BeanFactoryPostProcessor，调用顺序是BeanDefinitionRegistryPostProcessor优先于BeanFactoryPostProcessor执行，BeanFactoryPostProcessor优先于bean实例化执行。

public static void invokeBeanFactoryPostProcessors(
			ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {

		// Invoke BeanDefinitionRegistryPostProcessors first, if any.
		Set<String> processedBeans = new HashSet<>();
		//对于BeanDefinitionRegistry类型的处理
		if (beanFactory instanceof BeanDefinitionRegistry) {
			BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
			//创建两个list，分别是常规后处理器以及注册处理器
			List<BeanFactoryPostProcessor> regularPostProcessors = new LinkedList<>();
			List<BeanDefinitionRegistryPostProcessor> registryProcessors = new LinkedList<>();
			//遍历工厂后处理器
			for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
				if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
					BeanDefinitionRegistryPostProcessor registryProcessor =
							(BeanDefinitionRegistryPostProcessor) postProcessor;
							//调用postProcessBeanDefinitionRegistry方法并且将其添加到list
					registryProcessor.postProcessBeanDefinitionRegistry(registry);
					registryProcessors.add(registryProcessor);
				}
				else {
				//不调用方法，直接添加到对应list
					regularPostProcessors.add(postProcessor);
				}
			}

			// Do not initialize 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.
			// 用于保存当前处理的 BeanDefinitionRegistryPostProcessor
			List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();

			// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
			// 首先处理实现了 PriorityOrdered (有限排序接口)的 BeanDefinitionRegistryPostProcessor
			String[] postProcessorNames =
					beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
			for (String ppName : postProcessorNames) {
				if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
					currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
					processedBeans.add(ppName);
				}
			}
			// 排序
			sortPostProcessors(currentRegistryProcessors, beanFactory);
			// 加入registryProcessors集合
			registryProcessors.addAll(currentRegistryProcessors);
			// 调用所有实现了 PriorityOrdered 的 BeanDefinitionRegistryPostProcessors 的 postProcessBeanDefinitionRegistry()
			invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
			// 清空，以备下次使用
			currentRegistryProcessors.clear();

			// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
			// 其次，调用是实现了 Ordered（普通排序接口）的 BeanDefinitionRegistryPostProcessors
			postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
			for (String ppName : postProcessorNames) {
				if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
					currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
					processedBeans.add(ppName);
				}
			}
			sortPostProcessors(currentRegistryProcessors, beanFactory);
			registryProcessors.addAll(currentRegistryProcessors);
			invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
			currentRegistryProcessors.clear();

			// Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
			// 最后调用其他的 BeanDefinitionRegistryPostProcessors
			boolean reiterate = true;
			while (reiterate) {
				reiterate = false;
				postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
				for (String ppName : postProcessorNames) {
					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.
			invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
			invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
		}

		else {
			// Invoke factory processors registered with the context instance.
			// 如果不是 BeanDefinitionRegistry 只需要调用其回调函数（postProcessBeanFactory()）即可
			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!
		String[] postProcessorNames =
				beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

		// Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
		// Ordered, and the rest.
		// 这里同样需要区分 PriorityOrdered 、Ordered 和 no Ordered
		List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
		List<String> orderedPostProcessorNames = new ArrayList<>();
		List<String> nonOrderedPostProcessorNames = new ArrayList<>();
		for (String ppName : postProcessorNames) {
			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.
		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();
	}