Spring 初始化流程

開始

在SpringIOC中，前面講述了如何配置BeanDefinition和如何注冊BeanDefinition,但是這些知識容器初始化的一部分，在AbstractApplicationContext中的refresh()方法中，可以看到整個初始化過程。

今天就來看看這段曲折的初始化之路

編寫一個簡單的啟動類，打個斷點到AbstractApplicationContext中的refresh()方法中。

public class Application {
    public static void main(String[] args) {

        // setConfig -> call this.refresh()
        ClassPathXmlApplicationContext classPathXmlApplicationContext = new ClassPathXmlApplicationContext("context.xml");
    }
}

先看看refresh中調用了哪些方法：

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();
			}
		}
	}

一張圖概覽

上面的圖是整個初始化的大概流程。

然后把每一步拿出來說明一下吧

refresh()方法流程

文中使用了ClassPathXmlApplicationContext作為容器

1 prepareRefresh()

protected void prepareRefresh() {
    	// 記錄啟動時間 然后設立對應的標志位
		this.startupDate = System.currentTimeMillis();
		this.closed.set(false);
		this.active.set(true);

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

		// 這是擴展方法，由子類去實現
		initPropertySources();

		// 創建Environment，驗證必要的屬性
		getEnvironment().validateRequiredProperties();

		// 初始化容器，用於裝載早期的一些事件
		this.earlyApplicationEvents = new LinkedHashSet<>();
	}

這里主要是做一些准備工作

2 obtainFreshBeanFactory()

protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
    // 這個方法是子類去實現的
    refreshBeanFactory();
    // 創建ApplicationContext內部持有的BeanFactory
    // getBeanFactory也是留給子類去實現，可以查看AbstractRefreshableApplicationContext和GernericApplicationContext
    ConfigurableListableBeanFactory beanFactory = getBeanFactory();
    if (logger.isDebugEnabled()) {
        logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
    }
    return beanFactory;
}

3 prepareBeanFactory(beanFactory)

protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
		// 設置beanFactory的classLoader為當前context的classLoader
		beanFactory.setBeanClassLoader(getClassLoader());
		// 設置EL表達式解析器（Bean初始化完成后填充屬性時會用到）
		// spring3增加了表達式語言的支持，默認可以使用#{bean.xxx}的形式來調用相關屬性值
		beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
		// 設置屬性注冊解析器PropertyEditor 這個主要是對bean的屬性等設置管理的一個工具
		beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));
		
		// 注冊BeanPostProcessor-ApplicationContextAwareProcessor，從而在Aware接口實現類中的注入applicationContext等等
		// 添加了一個處理aware相關接口的beanPostProcessor擴展，主要是使用beanPostProcessor的postProcessBeforeInitialization()前置處理方法實現aware相關接口的功能
		// 類似的還有ResourceLoaderAware、ServletContextAware等等等等
		beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
    
		// 下面是忽略的自動裝配
		// 自動裝配模式下，下面這些接口的實現類，都不會自動裝配，自動裝配不是@Autowired
        // 注意區分ignoreDependencyType,這個是在自動裝配時忽略某個類型屬性的依賴
		beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
		beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
		beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
		beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
		beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
		beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);

		// 如果是BeanFactory的類，就注冊beanFactory
		//  如果是ResourceLoader、ApplicationEventPublisher、ApplicationContext等等就注入當前對象this(applicationContext對象)
		
		// 此處registerResolvableDependency()方法注意：它會把他們加入到DefaultListableBeanFactory的resolvableDependencies字段里面緩存這，供后面處理依賴注入的時候使用 DefaultListableBeanFactory#resolveDependency處理依賴關系
		// 這也是為什么我們可以通過依賴注入的方式，直接注入這幾個對象比如ApplicationContext可以直接依賴注入
		// 但是需要注意的是：這些Bean，Spring的IOC容器里其實是沒有的。beanFactory.getBeanDefinitionNames()和beanFactory.getSingletonNames()都是找不到他們的，所以特別需要理解這一點
		
		beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
		beanFactory.registerResolvableDependency(ResourceLoader.class, this);
		beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
		beanFactory.registerResolvableDependency(ApplicationContext.class, this);

		// 在Bean初始化后檢查是否實現了ApplicationListener接口
		// 是則加入當前的applicationContext的applicationListeners列表 
		beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));


		// 檢查容器中是否包含名稱為loadTimeWeaver的bean，實際上是增加Aspectj的支持
		// AspectJ采用編譯期織入、類加載期織入兩種方式進行切面的織入
		// 類加載期織入簡稱為LTW（Load Time Weaving）,通過特殊的類加載器來代理JVM默認的類加載器實現
		if (beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
			// 添加BEAN后置處理器：LoadTimeWeaverAwareProcessor
        	// 在BEAN初始化之前檢查BEAN是否實現了LoadTimeWeaverAware接口，
        	// 如果是，則進行加載時織入，即靜態代理。
			beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
			// Set a temporary ClassLoader for type matching.
			beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
		}

		// 注入一些其它信息的bean，比如environment、systemProperties、SystemEnvironment等
		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());
		}
	}

這里做的事情比較多，大多是和依賴的處理相關的配置。

4 postProcessBeanFactory(beanFactory)

這里是模板方法，留給子類去實現的邏輯，至此BeanFactory已經准備好

5 invokeBeanFactoryPostProcessors(beanFactory)

實例化並調用所有的BeanFactoryPostProcessor,當前必須是已經注冊的

protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
    // 調用BeanFactoryPostProcessor
   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)
    // 如果loadTimeWeaver這個Bean存在，那么就會配置上運行時織入的處理器LoadTimeWeaverAwareProcessor
   if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
      beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
      beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
   }
}

這里有個getBeanFactoryPostProcessors()方法，這個方法是獲取AbstractApplicationContext內部的一個List類型屬性，保存了手動添加的BeanPostProcessor實例。

重點在PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors中

public static void invokeBeanFactoryPostProcessors(
			ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {	
    // 先執行BeanDefinitionRegistryPostProcessors 
	// 需要注意的是BeanDefinitionRegistryPostProcessors 為 BeanFactoryPostProcessor 的子接口 它新增了方法：void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry)
	
	// 所以BeanDefinitionRegistryPostProcessors，它可以我們介入，改變Bean的一些定義信息，或者動態注入Bean定義
	Set<String> processedBeans = new HashSet<>();

	// 只有此beanFactory 是BeanDefinitionRegistry  才能執行BeanDefinitionRegistryPostProcessor
	if (beanFactory instanceof BeanDefinitionRegistry) {
		BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;

		// 此處安放了兩個容器，一個裝載普通的BeanFactoryPostProcessor
		// 另外一個裝載和Bean定義有關的 BeanDefinitionRegistryPostProcessor
		List<BeanFactoryPostProcessor> regularPostProcessors = new LinkedList<>();
		List<BeanDefinitionRegistryPostProcessor> registryProcessors = new LinkedList<>();

		// 這里是手動添加到ApplicationContext中的
		for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
			if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
				BeanDefinitionRegistryPostProcessor registryProcessor =
						(BeanDefinitionRegistryPostProcessor) postProcessor;
				
				// 這里執行post方法，然后然后吧它緩沖起來了，放在了registryProcessors里
				registryProcessor.postProcessBeanDefinitionRegistry(registry);
				registryProcessors.add(registryProcessor);
			}
			else {
				// 緩沖到普通的處理器
				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.
		// 接下來，就是去執行Spring容器里面的一些PostProcessor了。
		// 先執行實現了PriorityOrdered接口的，然后是Ordered接口的，最后執行剩下的
		List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();

		
	
		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);
		
		// 此處緩沖起來（需要注意的是，是排序后，再放進去的 這樣是最好的）
		registryProcessors.addAll(currentRegistryProcessors);

		
		invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
		// 此處把當前持有的執行對象給清空了，需要注意。以方便裝載后續執行的處理器們
		currentRegistryProcessors.clear();

		// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
		// 此處邏輯完全同上  處理實現Order接口的RegistryProcessors
		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.
		// 最后執行，兩個排序接口都沒有實現的BeanDefinitionRegistryPostProcessor們，並且也緩存起來
		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();
		}

	
		invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
		invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
	} else {
		// Invoke factory processors registered with the context instance.
		// 若是普通的Bean工廠，就直接執行set進來的后置處理器即可（因為容器里就沒有其它Bean定義了）
		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!
	// 下面就是開始執行BeanFactoryPostProcessor 基本也是按照上面的順序來執行的
	// 執行使用配置注冊的
	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) {

		// 這里面注意，已經執行過的后置處理器，就不要再執行了
		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();
}

這里核心就是調用手動添加到ApplicationContext中的BeanFactoryPostProcessor和使用配置注冊到BeanFactory的處理器。

但是同時要處理兩個問題：

• BeanFactoryPostProcessor的順序問題(實現了PriorityOrdered > 實現了Ordered > 什么都沒實現)
• 對於BeanDefinitionRegistryPostProcessor的處理,在這里面可以動態修改或者增加BeanDefinition

6 registerBeanPostProcessors(beanFactory)

注冊BeanPostProcessor

protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory) {
   PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, this);
}

重點戲還是在PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, this)

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

    // 從所與Bean定義中提取出BeanPostProcessor類型的Bean
   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.
    // BeanFactory中BeanPostProcessor的總數
   int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
    // 先注冊一個BeanPostProcessorChecker
    // 這個有什么用呢，下面我會說明
   beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

   // Separate between BeanPostProcessors that implement PriorityOrdered,
   // Ordered, and the rest.
    // 先按優先級，歸類了BeanPostProcessor
   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);
      }
   }

   // 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<>();
   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<>();
   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).
    // 把ApplicationListenerDetector 移動到最后
   beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}

這里我們獲取到了BeanFactory中定義的所有的BeanPostProcessor對象，並添加到AbstractBeanFactory中的List<BeanPostProcessor> beanPostProcessors中，以便后面創建bean的時候調用

這里有一個BeanPostProcessorChecker，這里是為了檢測創建Bean的時候是否所有的BeanPostProcessor都已經注冊好。

7 initMessageSource()

這部分邏輯比較簡單：向容器里注冊一個一個事件源的單例Bean：MessageSource

8 initApplicationEventMulticaster()

初始化Spring的事件多播器：ApplicationEventMulticaster

protected void initApplicationEventMulticaster() {
		ConfigurableListableBeanFactory beanFactory = getBeanFactory();
		if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {
			this.applicationEventMulticaster = beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);
		} else {
			this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory);
			beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, this.applicationEventMulticaster); 
		}
	}

檢測用戶是否自定義，沒有就創建默認的

9 onRefresh()

一個模板方法，留給子類實現

10 registerListeners()

上面的過程已經注冊好了事件多播器，現在注冊監聽器

protected void registerListeners() {
	
		for (ApplicationListener<?> listener : getApplicationListeners()) {
			// 把手動注冊的監聽器綁定到廣播器
			getApplicationEventMulticaster().addApplicationListener(listener);
		}

		// Do not initialize FactoryBeans here: We need to leave all regular beans
		// uninitialized to let post-processors apply to them!
		// 取到容器里面的所有的監聽器的名稱，綁定到廣播器  后面會廣播出去這些事件的
		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...
		// 如果存在早期應用事件，這里就直接發布了(同時就把earlyApplicationEvents該字段置為null)
		Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;
		this.earlyApplicationEvents = null;
		if (earlyEventsToProcess != null) {
			for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
				getApplicationEventMulticaster().multicastEvent(earlyEvent);
			}
		}
	}

11 finishBeanFactoryInitialization(beanFactory)

實例化所有單例的非懶加載的Bean,並完成依賴注入，這里有點復雜

protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
   // 初始化上下文的轉換服務，ConversionService是一個類型轉換接口
   if (beanFactory.containsBean(CONVERSION_SERVICE_BEAN_NAME) &&
         beanFactory.isTypeMatch(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class)) {
      beanFactory.setConversionService(
            beanFactory.getBean(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class));
   }

   // Register a default embedded value resolver if no bean post-processor
   // (such as a PropertyPlaceholderConfigurer bean) registered any before:
   // at this point, primarily for resolution in annotation attribute values.
   if (!beanFactory.hasEmbeddedValueResolver()) {
      beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
   }

   // Initialize LoadTimeWeaverAware beans early to allow for registering their transformers early.
   String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
   for (String weaverAwareName : weaverAwareNames) {
      getBean(weaverAwareName);
   }

   // 停止使用臨時的類加載器
   beanFactory.setTempClassLoader(null);

   // 緩存（凍結）所有的bean definition數據，不期望以后會改變
   beanFactory.freezeConfiguration();

   // 重要的方法  實例化所有剩余的單例Bean
   beanFactory.preInstantiateSingletons();
}

接下來就看這個重要的方法DefaultListableBeanFactory#preInstantiateSingletons

public void preInstantiateSingletons() throws BeansException {
		if (this.logger.isDebugEnabled()) {
			this.logger.debug("Pre-instantiating singletons in " + this);
		}

		// 獲取所有的beanName
		List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);

		// 初始化所有的非懶加載的單例bean
		for (String beanName : beanNames) {
			RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
            // 不是抽象類， 是單例的，不是懶加載的
			if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
                // 如果是工廠Bean，那就會此工廠Bean放進去
				if (isFactoryBean(beanName)) {
					final FactoryBean<?> factory = (FactoryBean<?>) getBean(FACTORY_BEAN_PREFIX + beanName);
					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 {
                    // 非FactoryBean初始化
					getBean(beanName);
				}
			}
		}

		// Trigger post-initialization callback for all applicable beans...
		for (String beanName : beanNames) {
			Object singletonInstance = getSingleton(beanName);
			if (singletonInstance instanceof SmartInitializingSingleton) {
				final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
				if (System.getSecurityManager() != null) {
					AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
						smartSingleton.afterSingletonsInstantiated();
						return null;
					}, getAccessControlContext());
				}
				else {
					smartSingleton.afterSingletonsInstantiated();
				}
			}
		}
	}

這里面通過FactoryBean定義的，它是懶加載的

創建Bean-getBean(beanName)方法

這里就是對於Bean的依賴的解析，完成Bean的創建，然后對Bean中的屬性完成注入。

由於這里內容較多，我們就放到下一次在總結。

12 finishRefresh()

protected void finishRefresh() {
   // Clear context-level resource caches (such as ASM metadata from scanning).
   clearResourceCaches();

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

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

   // Publish the final event.
   publishEvent(new ContextRefreshedEvent(this));

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

refresh完成后的一些處理

初始化聲明周期方法，發布事件等等