Spring Boot2.0版本源码(四)：Spring Boot的Bean的解析之refresh()方法

1. IOC思想

使用一个IOC去管理抽象bean的初始化，下面就是用一个@autowired注解完成animal的初始化，他可能是Dog也可能是Cat，我们无需关心它使用的是哪一个实现。以此降低类之间的耦合性。

下面是注入bean的五种方式

2. refresh()方法

看到SpringApplication的run()方法中会使用调用refreshContext(context);实现refresh操作

不断跟进源码,下面逐步解析refresh里面的各个方法

	@Override
	public void refresh() throws BeansException, IllegalStateException {
		synchronized (this.startupShutdownMonitor) {
			// Prepare this context for refreshing.
			prepareRefresh();

			// Tell the subclass to refresh the internal bean factory.
			ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

			// Prepare the bean factory for use in this context.
			prepareBeanFactory(beanFactory);

			try {
				// Allows post-processing of the bean factory in context subclasses.
				postProcessBeanFactory(beanFactory);

				// Invoke factory processors registered as beans in the context.
				invokeBeanFactoryPostProcessors(beanFactory);

				// Register bean processors that intercept bean creation.
				registerBeanPostProcessors(beanFactory);

				// Initialize message source for this context.
				initMessageSource();

				// Initialize event multicaster for this context.
				initApplicationEventMulticaster();

				// Initialize other special beans in specific context subclasses.
				onRefresh();

				// Check for listener beans and register them.
				registerListeners();

				// Instantiate all remaining (non-lazy-init) singletons.
				finishBeanFactoryInitialization(beanFactory);

				// Last step: publish corresponding event.
				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();
			}
		}
	}

2.1 prepareRefresh()方法

1.设置容器状态为active
2.初始化Conetext，将servletContext和servletConfig加载到spring环境中
3.设置环境必备的属性值

	@Override
	protected void prepareRefresh() {
		this.scanner.clearCache();// 清除本地的元数据缓存
		super.prepareRefresh();// 调用父类的prepareRefresh()
	}

/**
	 * Prepare this context for refreshing, setting its startup date and
	 * active flag as well as performing any initialization of property sources.
	 */
	protected void prepareRefresh() {
		// Switch to active.
		this.startupDate = System.currentTimeMillis();// 记录当前的容器时间
		// 上下文切换为active状态
		this.closed.set(false);
		this.active.set(true);

		// 如果当前处于debug模式会打印debug的日志
		if (logger.isDebugEnabled()) {
			if (logger.isTraceEnabled()) {
				logger.trace("Refreshing " + this);
			}
			else {
				logger.debug("Refreshing " + getDisplayName());
			}
		}

		// Initialize any placeholder property sources in the context environment.
		initPropertySources();// 初始化Conetext，将servletContext和servletConfig加载到spring环境中

		// Validate that all properties marked as required are resolvable:
		// see ConfigurablePropertyResolver#setRequiredProperties
		// 设置环境必备的属性值
		getEnvironment().validateRequiredProperties();

		// Store pre-refresh ApplicationListeners...
		// applicationListeners赋值给earlyApplicationListeners
		// applicationListeners就是系统的监听器
		if (this.earlyApplicationListeners == null) {
			this.earlyApplicationListeners = new LinkedHashSet<>(this.applicationListeners);
		}
		else {
			// Reset local application listeners to pre-refresh state.
			this.applicationListeners.clear();
			this.applicationListeners.addAll(this.earlyApplicationListeners);
		}

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

2.1.1 利用初始化器设置环境必备属性

application.properties中设置test的值

2.2 obtainFreshBeanFactory()获取bean工厂

1.设置beanFactory的序列化id
2.获取默认的beanFactory

	protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
		refreshBeanFactory();// 设置序列化id
		return getBeanFactory();// 获取默认的beanFactory
	}

2.2.1 refreshBeanFactory()设置序列化id

	/**
	 * Do nothing: We hold a single internal BeanFactory and rely on callers
	 * to register beans through our public methods (or the BeanFactory's).
	 * @see #registerBeanDefinition
	 */
	@Override
	protected final void refreshBeanFactory() throws IllegalStateException {
		if (!this.refreshed.compareAndSet(false, true)) {
			throw new IllegalStateException(
					"GenericApplicationContext does not support multiple refresh attempts: just call 'refresh' once");
		}
		// 设置序列化id
		this.beanFactory.setSerializationId(getId());
	}

2.2.2 getBeanFactory()获取默认beanFactory

	private final DefaultListableBeanFactory beanFactory;
		
	//中间省略大量代码
	
	/**
	 * Return the single internal BeanFactory held by this context
	 * (as ConfigurableListableBeanFactory).
	 */
	@Override
	public final ConfigurableListableBeanFactory getBeanFactory() {
		// 获取默认的beanFactory
		return this.beanFactory;
	}

2.3 prepareBeanFactory(beanFactory)源码

1.设置beanFactory的一些属性
2.添加后置处理器
3.设置忽略的自动装配接口
4.注册一些bean组件

 /**
	 * Configure the factory's standard context characteristics,
	 * such as the context's ClassLoader and post-processors.
	 * @param beanFactory the BeanFactory to configure
	 */
	protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
		// Tell the internal bean factory to use the context's class loader etc.
		// beanFactory设置类加载器
		beanFactory.setBeanClassLoader(getClassLoader());
		// beanFactory设置解析器，解析Spel表达式
		beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
		// beanFactory设置属性转化器
		beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));

		// Configure the bean factory with context callbacks.
		// beanFactory添加后置处理器
		beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
		// 忽略下面这些接口的装配关系
		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.
		// 下面这下操作都是有该类来处理，这些依赖指向自身
		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.
		// 添加后置处理器
		beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));

		// Detect a LoadTimeWeaver and prepare for weaving, if found.
		// 查看beanFactory中是否含有下面的这些bean。没有就注册一个这样的bean
		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.
		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());
		}
	}

2.4 postProcessBeanFactory(beanFactory)源码

postProcessBeanFactory(beanFactory)通常都是被子类重写，添加一些web环境相关的组件。
跟进源码：

	/**
	 * Register ServletContextAwareProcessor.
	 * @see ServletContextAwareProcessor
	 */
	@Override
	protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
		// 添加WebApplicationContextServletContextAwareProcessor后置处理器
		beanFactory.addBeanPostProcessor(new WebApplicationContextServletContextAwareProcessor(this));
		// 增加忽略的装配处理接口ServletContextAware
		beanFactory.ignoreDependencyInterface(ServletContextAware.class);
		// 注册web环境和作用域，还有注册request、response和session的解析的依赖
		registerWebApplicationScopes();
	}

2.5 invokeBeanFactoryPostProcessors(beanFactory)源码

里面的核心是一个同名方法

/**
	 * Instantiate and invoke all registered BeanFactoryPostProcessor beans,
	 * respecting explicit order if given.
	 * <p>Must be called before singleton instantiation.
	 */
	protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
		// getBeanFactoryPostProcessors()会获取一个后置处理器的list，这些后置处理器都是listener初始化的时候注入的
		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()));
		}
	}

继续跟进invokeBeanFactoryPostProcessors()方法

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<>();

			// 遍历之前获得的后置处理器集合
			for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
				// 将后置处理器添加到registryProcessors和regularPostProcessors集合中
				if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
					BeanDefinitionRegistryPostProcessor registryProcessor =
							(BeanDefinitionRegistryPostProcessor) postProcessor;
					registryProcessor.postProcessBeanDefinitionRegistry(registry);
					registryProcessors.add(registryProcessor);
				}
				else {
					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.
			List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();

			// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
			// 获取所有的beanFactory的实现
			String[] postProcessorNames =
					beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
			// 遍历这些beanFactory
			for (String ppName : postProcessorNames) {
				// 如果beanFactory实现了PriorityOrdered接口，就将他加入currentRegistryProcessors和processedBeans集合中
				if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
					currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
					processedBeans.add(ppName);
				}
			}
			// 对currentRegistryProcessors排序
			sortPostProcessors(currentRegistryProcessors, beanFactory);
			// 将currentRegistryProcessors加入到registryProcessors
			registryProcessors.addAll(currentRegistryProcessors);
			// 调用currentRegistryProcessors中的所有类的registry方法
			invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
			currentRegistryProcessors.clear();

			// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
			// 获取beanFactory中所有BeanDefinitionRegistryPostProcessor的实现
			postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
			for (String ppName : postProcessorNames) {
				// 遍历这下实现，如果实现了Ordered接口，则将他们加入到currentRegistryProcessors中
				if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
					currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
					processedBeans.add(ppName);
				}
			}
			// 对他们排序
			sortPostProcessors(currentRegistryProcessors, beanFactory);
			// registryProcessors中加入currentRegistryProcessors
			registryProcessors.addAll(currentRegistryProcessors);
			// 再次调用currentRegistryProcessors中所有类的registry方法
			invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
			currentRegistryProcessors.clear();

			// Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
			// 接下来也是重复上面的步骤，
			// 因为实现InstantiationAwareBeanPostProcessor接口口注入bean，有可能注入一个实现了InstantiationAwareBeanPostProcessor接口
			// 的bean，所以我们需要继续判断此时的beanFactory中是否还需要完成下一次扫描
			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.
			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beanFactory中BeanFactoryPostProcessor的实现
		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) {
			if (processedBeans.contains(ppName)) {
				// skip - already processed in first phase above
			}
			// 如果beanFactory实现了PriorityOrdered接口，加入到priorityOrderedPostProcessors队列中
			else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
				priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
			}
			// 如果beanFactory实现了Ordered接口，加入到orderedPostProcessorNames队列中
			else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
				orderedPostProcessorNames.add(ppName);
			}
			// 否则加入到nonOrderedPostProcessorNames对列中
			else {
				nonOrderedPostProcessorNames.add(ppName);
			}
		}

		// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
		// priorityOrderedPostProcessors集合中的类调用postProcessBeanFactory方法
		sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
		invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

		// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
		// orderedPostProcessors集合中的类排序后调用postProcessBeanFactory方法
		List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
		for (String postProcessorName : orderedPostProcessorNames) {
			orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
		}
		sortPostProcessors(orderedPostProcessors, beanFactory);
		invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);

		// Finally, invoke all other BeanFactoryPostProcessors.
		// nonOrderedPostProcessors集合中的类调用postProcessBeanFactory方法
		List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
		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();//清空上面是产生的缓存
	}

总结

步骤2和3只有判断条件不同


以上步骤都是为了如下图所示的方式注入bean，因为注入的bean可能本身实现了BeanDefinitionRegistryPostProcessor，就需要再次循环将当前新增的BeanDefinitionRegistryPostProcessor实现类中方法调用注入新的bean

postProcessBeanFactory方法通常用于给bean设置属性等操作

也就是说整个该方法做了两件事情

2.6 registerBeanPostProcessors(beanFactory)源码

该方法重要是在invokeBeanFactoryPostProcessors()方法完成bean的初始化之后去完成beanPostProcessor这一类的bean的按照是否实现order或PriorityOrdered这两类接口分类后的每一类的beanPostProcessor都有序，然后重新注入到beanFactory中

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

		// 从beanFactory中获取BeanPostProcessor的实现
		String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);

		// Register BeanPostProcessorChecker that logs an info message when
		// a bean is created during BeanPostProcessor instantiation, i.e. when
		// a bean is not eligible for getting processed by all BeanPostProcessors.
		int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
		// 将BeanPostProcessorChecker添加到beanFactory
		beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

		// Separate between BeanPostProcessors that implement PriorityOrdered,
		// Ordered, and the rest.
		List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
		List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
		List<String> orderedPostProcessorNames = new ArrayList<>();
		List<String> nonOrderedPostProcessorNames = new ArrayList<>();
		for (String ppName : postProcessorNames) {
			// 如果当前BeanPostProcessor的实现也实现了PriorityOrdered接口，则添加到priorityOrderedPostProcessors集合中
			if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
				BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
				priorityOrderedPostProcessors.add(pp);
				if (pp instanceof MergedBeanDefinitionPostProcessor) {
					internalPostProcessors.add(pp);
				}
			}
			// 如果当前BeanPostProcessor的实现也实现了Ordered接口，则添加到orderedPostProcessorNames集合中
			else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
				orderedPostProcessorNames.add(ppName);
			}
			//否则添加到nonOrderedPostProcessorNames集合中
			else {
				nonOrderedPostProcessorNames.add(ppName);
			}
		}

		// 下面三步，也是根据PriorityOrdered、Ordered和什么都没有实现的类分为三类bean
		// 每一类bean各自排序后调用添加到beanFactory的beanPostProcessor的集合中
		// 疑问：原来就有的bean为什么会被重新添加一次，数据是否重复？
		// 答案：不会重复，原来的bean会被删除，我们这一步只是将无序的bean排序后重新添加
		// First, register the BeanPostProcessors that implement PriorityOrdered.
		sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
		registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

		// Next, register the BeanPostProcessors that implement Ordered.
		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);

		// Now, register all regular 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));
	}

2.7 initMessageSource()源码

// 这里主要是国家化多语言的配置
	protected void initMessageSource() {
		ConfigurableListableBeanFactory beanFactory = getBeanFactory();
		if (beanFactory.containsLocalBean(MESSAGE_SOURCE_BEAN_NAME)) {
			// 查看beanFactory中是否有messageSource
			this.messageSource = beanFactory.getBean(MESSAGE_SOURCE_BEAN_NAME, MessageSource.class);
			// Make MessageSource aware of parent MessageSource.
			if (this.parent != null && this.messageSource instanceof HierarchicalMessageSource) {
				HierarchicalMessageSource hms = (HierarchicalMessageSource) this.messageSource;
				if (hms.getParentMessageSource() == null) {
					// Only set parent context as parent MessageSource if no parent MessageSource
					// registered already.
					hms.setParentMessageSource(getInternalParentMessageSource());
				}
			}
			if (logger.isTraceEnabled()) {
				logger.trace("Using MessageSource [" + this.messageSource + "]");
			}
		}
		// 没有messageSource就构建一个messageSource实现类加入到beanFactory中
		else {
			// Use empty MessageSource to be able to accept getMessage calls.
			DelegatingMessageSource dms = new DelegatingMessageSource();
			dms.setParentMessageSource(getInternalParentMessageSource());
			this.messageSource = dms;
			beanFactory.registerSingleton(MESSAGE_SOURCE_BEAN_NAME, this.messageSource);
			if (logger.isTraceEnabled()) {
				logger.trace("No '" + MESSAGE_SOURCE_BEAN_NAME + "' bean, using [" + this.messageSource + "]");
			}
		}
	}

2.8 initApplicationEventMulticaster()源码

该方法主要是向beanFactory中添加一个广播器

// 初始化一个监听器的广播器
	protected void initApplicationEventMulticaster() {
		ConfigurableListableBeanFactory beanFactory = getBeanFactory();
		// beanFactory中有广播器
		if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {
			this.applicationEventMulticaster =
					beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);
			if (logger.isTraceEnabled()) {
				logger.trace("Using ApplicationEventMulticaster [" + this.applicationEventMulticaster + "]");
			}
		}
		// 没有广播器则添加一个广播器
		else {
			this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory);
			beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, this.applicationEventMulticaster);
			if (logger.isTraceEnabled()) {
				logger.trace("No '" + APPLICATION_EVENT_MULTICASTER_BEAN_NAME + "' bean, using " +
						"[" + this.applicationEventMulticaster.getClass().getSimpleName() + "]");
			}
		}
	}

2.9 onRefresh()源码

主要是一个预留的方法，交给子类去实现，通常都是创建一个tomcat容器

// 该方法用于构建一个tomcat容器
	/**
	 * Template method which can be overridden to add context-specific refresh work.
	 * Called on initialization of special beans, before instantiation of singletons.
	 * <p>This implementation is empty.
	 * @throws BeansException in case of errors
	 * @see #refresh()
	 */
	protected void onRefresh() throws BeansException {
		// For subclasses: do nothing by default.
	}

2.10 registerListeners()源码

1.主要就是用于将监听器加入到多播器中
2.然后将早期没有处理的事件完成

	// 向多播器中注入listener
	protected void registerListeners() {
		// Register statically specified listeners first.
		for (ApplicationListener<?> listener : getApplicationListeners()) {
			getApplicationEventMulticaster().addApplicationListener(listener);
		}

		// Do not initialize FactoryBeans here: We need to leave all regular beans
		// uninitialized to let post-processors apply to them!
		String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);
		for (String listenerBeanName : listenerBeanNames) {
			getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);
		}

		// Publish early application events now that we finally have a multicaster...
		// earlyApplicationEvents中保存的是多播器初始化完成但是监听器还没有初始化完成，
		// 如果此调用多播器发布监听事件，就会先保存到earlyApplicationEvents中
		// 等到监听器初始化完成了再去触发这些发布的事件
		Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;
		this.earlyApplicationEvents = null;
		if (earlyEventsToProcess != null) {
			for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
				getApplicationEventMulticaster().multicastEvent(earlyEvent);
			}
		}
	}

2.11 finishBeanFactoryInitialization()源码

主要是用于完成一些单例bean的初始化

@Override
	public void preInstantiateSingletons() throws BeansException {
		if (logger.isTraceEnabled()) {
			logger.trace("Pre-instantiating singletons in " + this);
		}

		// Iterate over a copy to allow for init methods which in turn register new bean definitions.
		// While this may not be part of the regular factory bootstrap, it does otherwise work fine.
		// 获取到所有的beanDefinition的名称
		List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);

		// Trigger initialization of all non-lazy singleton beans...
		for (String beanName : beanNames) {
			// BeanDefinition主要是描述某一个bean的信息，比如当前bean是否是单例
			RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
			// 判断对象是否单例
			if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
				// 如果当前bean是工厂，就会为其设置一个工厂的标志位
				if (isFactoryBean(beanName)) {
					Object bean = getBean(FACTORY_BEAN_PREFIX + beanName);
					if (bean instanceof FactoryBean) {
						final FactoryBean<?> factory = (FactoryBean<?>) bean;
						boolean isEagerInit;
						if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
							isEagerInit = AccessController.doPrivileged((PrivilegedAction<Boolean>)
											((SmartFactoryBean<?>) factory)::isEagerInit,
									getAccessControlContext());
						}
						else {
							isEagerInit = (factory instanceof SmartFactoryBean &&
									((SmartFactoryBean<?>) factory).isEagerInit());
						}
						if (isEagerInit) {
							getBean(beanName);
						}
					}
				}
				else { //直接实例化这个bean
					getBean(beanName);
				}
			}
		}

2.12 finishRefresh()源码

1.清空之前的很多缓存
2.初始化生命周期处理器
3.调用生命周期处理器的onRefresh()方法
4.发送一个ContextRefreshedEvent事件
4.JMX相关的处理

/**
	 * Finish the refresh of this context, invoking the LifecycleProcessor's
	 * onRefresh() method and publishing the
	 * {@link org.springframework.context.event.ContextRefreshedEvent}.
	 */
	protected void finishRefresh() {
		// Clear context-level resource caches (such as ASM metadata from scanning).
		clearResourceCaches();// 清空缓存

		// Initialize lifecycle processor for this context.
		initLifecycleProcessor();

		// Propagate refresh to lifecycle processor first.
		getLifecycleProcessor().onRefresh();

		// Publish the final event.
		publishEvent(new ContextRefreshedEvent(this));// 发送一个ContextRefreshedEvent事件

		// Participate in LiveBeansView MBean, if active.
		LiveBeansView.registerApplicationContext(this);
	}