【spring源码分析】IOC容器初始化（五）

前言：前几篇文章已经将BeanDefinition的加载过程大致分析完成，接下来继续分析其他过程。

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AbstractApplicationContext#refresh

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

             // Tell the subclass to refresh the internal bean factory.
             // 创建并初始化BeanFactory
             ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

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

             try {
                 // Allows post-processing of the bean factory in context subclasses.
                 // 提供子类覆盖的额外处理，即子类处理定义的BeanFactoryPostProcess
                 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.
                 // 注册拦截Bean创建的Bean处理器，即注册BeanPostProcessor
                 registerBeanPostProcessors(beanFactory);

                 // Initialize message source for this context.
                 // 初始化上下文中的资源文件，如国际化文件的处理
                 initMessageSource();

                 // Initialize event multicaster for this context.
                 // 初始化上下文事件广播器
                 initApplicationEventMulticaster();

                 // Initialize other special beans in specific context subclasses.
                 // 给子类扩展初始化其他bean
                 onRefresh();

                 // Check for listener beans and register them.
                 // 在所有bean中查找listener bean，然后注册到广播器中
                 registerListeners();

                 // Instantiate all remaining (non-lazy-init) singletons.
                 // 初始化剩下的单例Bean(非延迟加载的)
                 finishBeanFactoryInitialization(beanFactory);

                 // Last step: publish corresponding event.
                 // 完成刷新过程，通知声明周期处理器lifecycleProcessor刷新过程，同时发出ContextRefreshEvent事件通知别人
                 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.
                 // 销毁已经创建的bean
                 destroyBeans();

                 // Reset 'active' flag.
                 // 重置容器激活标签
                 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();
             }
         }
     }

再次回到refresh函数中，前面已经将preparRefresh和obtainFreshBeanFactory函数进行了分析，特别是obtainFreshBeanFactory引申出了非常多的内容，接下来我们看prepareBeanFactory函数。

AbstractApplicationContext#prepareBeanFactory

 protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
         // Tell the internal bean factory to use the context's class loader etc.
         // 设置beanFactory的classLoader
         beanFactory.setBeanClassLoader(getClassLoader());
         // 设置beanFactory的表达式语言处理器，Spring3开始增加了对语言表达式，默认可以使用#{bean.xxx}的形式来调用相关属性值
         beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
         // 为beanFactory增加一个默认的propertyEditor
         beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));

         // Configure the bean factory with context callbacks.
         // 添加ApplicationContextAwareProcessor
         beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
         // 设置忽略自动装配的接口
         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.
         // 设置几个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.
         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.
         // 注册默认的系统环境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());
         }
     }

分析：

该函数的逻辑比较简单，就是对BeanFactory的一些属性进行填充，为后期实例化Bean做准备。

AbstractApplicationContext#postProcessBeanFactory该函数的默认实现为空，主要提供给子类进行自定义处理，增强扩展性。

AbstractApplicationContext#invokeBeanFactoryPostProcessors

     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()));
         }
     }

分析：

该函数的作用是激活BeanFactory的一些处理器。主要逻辑在PostProcessorRegistrationDelegate#invokeBeanFactoryPostProcessors

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

         // Invoke BeanDefinitionRegistryPostProcessors first, if any.
         // 定义一个set保存所有BeanFactoryPostProcessors
         Set<String> processedBeans = new HashSet<>();

         // 如果当前BeanFactory为BeanDefinitionRegistry
         if (beanFactory instanceof BeanDefinitionRegistry) {
             BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
             // BeanFactoryPostProcessor集合
             List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
             // BeanDefinitionRegistryPostProcessor集合
             List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();

             // 遍历beanFactoryPostProcessors
             for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
                 // 如果是BeanDefinitionRegistryPostProcessor，则调用BeanDefinitionRegistryPostProcessor进行注册
                 // 同时加入到registryProcessors集合中
                 if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
                     BeanDefinitionRegistryPostProcessor registryProcessor =
                             (BeanDefinitionRegistryPostProcessor) postProcessor;
                     registryProcessor.postProcessBeanDefinitionRegistry(registry);
                     registryProcessors.add(registryProcessor);
                 } else {
                     // 否则当做普通的BeanFactoryPostProcessor处理，添加到regularPostProcessors集合中，便于后续处理
                     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(邮箱排序接口)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BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry()
             invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
             // 清空，以备下次使用
             currentRegistryProcessors.clear();

             // Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
             // 其次，调用实现了Ordered(普通排序接口)的BeanDefinitionRegistryPostProcessor
             // 逻辑与上面相同
             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;
                 // 获取BeanDefinitionRegistryPostProcessors
                 postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
                 for (String ppName : postProcessorNames) {
                     // 没有包含在processBeans中的(因为包含的都已经处理了)
                     if (!processedBeans.contains(ppName)) {
                         currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                         processedBeans.add(ppName);
                         reiterate = true;
                     }
                 }
                 // 同样的逻辑
                 sortPostProcessors(currentRegistryProcessors, beanFactory);
                 registryProcessors.addAll(currentRegistryProcessors);
                 invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
                 currentRegistryProcessors.clear();
             }

             // Now, invoke the postProcessBeanFactory callback of all processors handled so far.
             // 调用所有BeanDefinitionRegistryPostProcessor(包括手动注册和通过配置文件注册)和BeanFactoryPostProcessor(只有手动注册)的回调函数(postProcessBeanFactory)
             invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
             invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
         } else {
             // 如果不是BeanDefinitionRegistry只需调用其回调函数(postProcessBeanFactory())即可
             // 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!
         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和没有排序的
         List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
         List<String> orderedPostProcessorNames = new ArrayList<>();
         List<String> nonOrderedPostProcessorNames = new ArrayList<>();
         for (String ppName : postProcessorNames) {
             // 已经处理过，则跳过
             if (processedBeans.contains(ppName)) {
                 // skip - already processed in first phase above
             } else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) { // PriorityOrdered
                 priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
             } else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {  // Ordered
                 orderedPostProcessorNames.add(ppName);
             } else {// 未排序的
                 nonOrderedPostProcessorNames.add(ppName);
             }
         }

         // First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
         // PriorityOrdered接口
         sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
         invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

         // Next, invoke the BeanFactoryPostProcessors that implement Ordered.
         // Ordered接口
         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.
         // 未排序的接口
         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();
     }

分析：

上述代码较长，但是处理逻辑较为单一，就是对所有的 BeanDefinitionRegistryPostProcessors 、手动注册的 BeanFactoryPostProcessor 以及通过配置文件方式的 BeanFactoryPostProcessor 按照PriorityOrdered 、 Ordered、nonOrdered 三种方式分开处理、调用。

PostProcessorRegistrationDelegate#registerBeanPostProcessors

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

         // 获取所有的BeanPostProcessor的beanName
         // 这些beanName都已经全部加载到容器中去，但是没有实例化
         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.
         // 记录所有的beanProcessor数量
         int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
         // 注册BeanPostProcessorChecker，它主要用于在BeanPostProcessor实例化期间记录日志
         // 当Spring中高配置的后置处理器还没有注册就已经开始了bean的实例化过程，这个时候便会打印BeanPostProcessorChecker中的内容
         beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

         // Separate between BeanPostProcessors that implement PriorityOrdered,
         // Ordered, and the rest.
         // priorityOrderedPostProcessors保证顺序
         List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
         List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
         // 使用Ordered保证顺序
         List<String> orderedPostProcessorNames = new ArrayList<>();
         // 没有顺序
         List<String> nonOrderedPostProcessorNames = new ArrayList<>();
         for (String ppName : postProcessorNames) {
             // PriorityOrdered
             if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
                 // 调用getBean获取bean实例对象
                 BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
                 priorityOrderedPostProcessors.add(pp);
                 if (pp instanceof MergedBeanDefinitionPostProcessor) {
                     internalPostProcessors.add(pp);
                 }
             } else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
                 // 有序
                 orderedPostProcessorNames.add(ppName);
             } else {
                 // 无序
                 nonOrderedPostProcessorNames.add(ppName);
             }
         }

         // First, register the BeanPostProcessors that implement PriorityOrdered.
         // 第一步：注册所有实现了PriorityOrdered的BeanPostProcessor
         // 排序
         sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
         // 注册
         registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

         // Next, register the BeanPostProcessors that implement Ordered.
         // 第二步：注册所有实现了Ordered的BeanPostProcessor
         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);
             }
         }
         // 排序
         sortPostProcessors(orderedPostProcessors, beanFactory);
         // 注册
         registerBeanPostProcessors(beanFactory, orderedPostProcessors);

         // Now, register all regular BeanPostProcessors.
         // 第三步：注册所有无序的BeanPostProcessor
         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);
             }
         }
         // 无序的注册，不需要排序
         registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);

         // Finally, re-register all internal BeanPostProcessors.
         // 最后注册所有MergedBeanDefinitionPostProcessor类型的BeanPostProcessor
         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).
         // 加入ApplicationListenerDetector(探测器)
         // 重新注册BeanPostProcessor以检测内部bean，因为ApplicationListenerDetector将其移动到处理器链的末尾
         beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
     }

分析：

上述代码虽稍微有一点长，但整体逻辑还是比较简单，就是对BeanPostProcessor进行注册，按照PriorityOrdered 、 Ordered、nonOrdered三种分支进行处理。

AbstractApplicationContext#initMessageSource

 protected void initMessageSource() {
         ConfigurableListableBeanFactory beanFactory = getBeanFactory();
         // 包含"messageSource"bean
         if (beanFactory.containsLocalBean(MESSAGE_SOURCE_BEAN_NAME)) {
             this.messageSource = beanFactory.getBean(MESSAGE_SOURCE_BEAN_NAME, MessageSource.class);
             // Make MessageSource aware of parent MessageSource.
             // 如果有父类
             // HierarchicalMessageSource分级处理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.
                     // 如果没有注册父MessageSource，则设置为父类上下文的MessageSource
                     hms.setParentMessageSource(getInternalParentMessageSource());
                 }
             }
             if (logger.isTraceEnabled()) {
                 logger.trace("Using MessageSource [" + this.messageSource + "]");
             }
         } else {
             // 使用空MessageSource
             // 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 + "]");
             }
         }
     }

分析：

这里主要初始化MessageSource接口实现类，主要用于国际化。

AbstractApplicationContext#initApplicationEventMulticaster

 protected void initApplicationEventMulticaster() {
         ConfigurableListableBeanFactory beanFactory = getBeanFactory();
         // 如果存在applicationEventMulticaster bean，则获取赋值
         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 + "]");
             }
         } else {
             // 如果没有，则新建SimpleApplicationEventMulticaster，并完成bean的注册
             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() + "]");
             }
         }
     }

分析：

初始化上下文事件广播器，如果当前容器中存在 applicationEventMulticaster 的 bean，则对 applicationEventMulticaster 赋值，否则新建一个 SimpleApplicationEventMulticaster 的对象（默认的），并完成注册。

AbstractApplicationContext#onRefresh

预留给 AbstractApplicationContext 的子类用于初始化其他特殊的 bean，该方法需要在所有单例 bean 初始化之前调用。

AbstractApplicationContext#registerListeners

 protected void registerListeners() {
         // Register statically specified listeners first.
         // 注册静态监听器
         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...
         // 至此，已经完成将监听器注册到ApplicationEventMulticaster中，下面将发布前期的事件给监听器
         Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;
         this.earlyApplicationEvents = null;
         if (earlyEventsToProcess != null) {
             for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
                 getApplicationEventMulticaster().multicastEvent(earlyEvent);
             }
         }
     }

分析：在所有 bean中查找 listener bean，然后注册到广播器中。

AbstractApplicationContext#finishBeanFactoryInitialization

 protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
         // Initialize conversion service for this context.
         // 初始化转换器
         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.
         // 如果之前没有注册bean后置处理器，则注册默认的解析器
         if (!beanFactory.hasEmbeddedValueResolver()) {
             beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
         }

         // 初始化 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);
         }

         // Stop using the temporary ClassLoader for type matching.
         // 停止使用临时的classLoader
         beanFactory.setTempClassLoader(null);

         // Allow for caching all bean definition metadata, not expecting further changes.
         beanFactory.freezeConfiguration();

         // Instantiate all remaining (non-lazy-init) singletons.
         // 初始化所有剩余的单例(非延迟初始化)
         beanFactory.preInstantiateSingletons();
     }

分析：初始化剩下的单例Bean(非延迟加载的)

AbstractApplicationContext#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);
     }

分析：完成刷新过程,通知生命周期处理器 lifecycleProcessor 刷新过程,同时发出 ContextRefreshEvent 通知别人

总结

本文只是对AbstractApplicationContext的一些方法进行了简要介绍，并没有进行非常详细的分析，因为加载BeanDefinition阶段才是我们的重点，现在BeanDefinition有了，接下来就是看spring是如何实例化Bean了。

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by Shawn Chen，2018.12.25日，晚。