【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。