前面的章節(jié)介紹了SpringIoC的基礎(chǔ)容器BeanFactory，接下來(lái)的章節(jié)分析Spring的高級(jí)容器ApplicationContext。關(guān)于兩者的介紹，可以參考以前的章節(jié)。接下來(lái)我們以ClassPathXmlApplicationContext為例分析ApplicationContext的創(chuàng)建過(guò)程。

引、ApplicationContext創(chuàng)建過(guò)程簡(jiǎn)析

/**
 * 創(chuàng)建一個(gè)新的ClassPathXmlApplicationContext容器
 * 從指定的xml文件加載BeanDefinition并自動(dòng)刷新容器
 * @param configLocation 配置文件位置
 * @throws BeansException 容器創(chuàng)建失敗，拋出BeansException異常
 */
public ClassPathXmlApplicationContext(String configLocation) throws BeansException {
    this(new String[] {configLocation}, true, null);
}

public ClassPathXmlApplicationContext(String[] configLocations, boolean refresh, @Nullable ApplicationContext parent) throws BeansException {
    // 調(diào)用父類構(gòu)造器
    super(parent);
    // 設(shè)定配置文件路徑
    setConfigLocations(configLocations);
    if (refresh) {
        // 擴(kuò)展功能
        refresh();
    }
}

public void refresh() throws BeansException, IllegalStateException {
    synchronized (this.startupShutdownMonitor) {
        // 1、準(zhǔn)備刷新上下文環(huán)境
        prepareRefresh();
        // 2、讀取xml并初始化BeanFactory
        ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
        // 3、填充BeanFactory功能
        prepareBeanFactory(beanFactory);
        try {
            // 4、子類覆蓋方法額外處理(空方法)
            postProcessBeanFactory(beanFactory);
            // 5、調(diào)動(dòng)BeanFactoryPostProcessor
            invokeBeanFactoryPostProcessors(beanFactory);
            // 6、注冊(cè)BeanPostProcessors
            registerBeanPostProcessors(beanFactory);
            // 7、初始化Message資源
            initMessageSource();
            // 8、初始事件廣播器
            initApplicationEventMulticaster();
            // 9、留給子類初始化其他Bean(空的模板方法)
            onRefresh();
            // 10、注冊(cè)事件監(jiān)聽器
            registerListeners();
            // 11、初始化其他的單例Bean(非延遲加載的)
            finishBeanFactoryInitialization(beanFactory);
            // 12、完成刷新過(guò)程,通知生命周期處理器lifecycleProcessor刷新過(guò)程,同時(shí)發(fā)出ContextRefreshEvent通知
            finishRefresh();
        }
        catch (BeansException ex) {
            // 13、銷毀已經(jīng)創(chuàng)建的Bean
            destroyBeans();
            // 14、重置容器激活標(biāo)簽
            cancelRefresh(ex);
            throw ex;
        }
        finally {
            resetCommonCaches();
        }
    }
}

逐步分析refresh()方法。

1、prepareRefresh刷新上下文的準(zhǔn)備工作

/**
 * 準(zhǔn)備刷新上下文環(huán)境，設(shè)置它的啟動(dòng)日期和活動(dòng)標(biāo)志，以及執(zhí)行任何屬性源的初始化。
 * Prepare this context for refreshing, setting its startup date and
 * active flag as well as performing any initialization of property sources.
 */
protected void prepareRefresh() {
    this.startupDate = System.currentTimeMillis();
    this.closed.set(false);
    this.active.set(true);

    // 在上下文環(huán)境中初始化任何占位符屬性源。(空的方法,留給子類覆蓋)
    initPropertySources();

    // 驗(yàn)證需要的屬性文件是否都已放入環(huán)境中
    getEnvironment().validateRequiredProperties();

    // 允許收集早期的應(yīng)用程序事件，一旦有了多播器，就可以發(fā)布……
    this.earlyApplicationEvents = new LinkedHashSet<>();
}

2、obtainFreshBeanFactory->讀取xml并初始化BeanFactory

protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
    // 刷新BeanFactory并返回BeanFactory對(duì)象
    refreshBeanFactory();
    return getBeanFactory();
}

protected final void refreshBeanFactory() throws BeansException {
    // 1、如果BeanFactory的實(shí)例已經(jīng)存在,則銷毀并關(guān)閉
    if (hasBeanFactory()) {
        destroyBeans();
        closeBeanFactory();
    }
    // 2、重新創(chuàng)建BeanFactory
    try {
        // 創(chuàng)建BeanFactory
        DefaultListableBeanFactory beanFactory = createBeanFactory();
        // 為BeanFactory設(shè)置id
        beanFactory.setSerializationId(getId());
        // 定制beanFactory
        customizeBeanFactory(beanFactory);
        // 加載BeanDefinition
        loadBeanDefinitions(beanFactory);
        synchronized (this.beanFactoryMonitor) {
            this.beanFactory = beanFactory;
        }
    }
    catch (IOException ex) {
        throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
    }
}

該方法的主要作用就是保證獲取一個(gè)全新的beanFactory，關(guān)于beanFactory我們?cè)谇懊嬉呀?jīng)做了很多介紹了，這里不在說(shuō)明。

3、prepareBeanFactory-->填充BeanFactory功能

protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
    // Tell the internal bean factory to use the context's class loader etc.
    // 設(shè)置beanFactory的classLoader
    beanFactory.setBeanClassLoader(getClassLoader());
    // 設(shè)置beanFactory的表達(dá)式語(yǔ)言處理器,Spring3開始增加了對(duì)語(yǔ)言表達(dá)式的支持,默認(rèn)可以使用#{bean.xxx}的形式來(lái)調(diào)用相關(guān)屬性值
    beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
    // 為beanFactory增加一個(gè)默認(rèn)的propertyEditor,這個(gè)主要是對(duì)bean的屬性等設(shè)置管理的一個(gè)工具
    beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));

    // Configure the bean factory with context callbacks.
    // 添加ApplicationContextAwareProcessor
    beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));

    // 設(shè)置忽略自動(dòng)裝配的接口
    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.
    // 設(shè)置幾個(gè)自動(dòng)裝配的特殊規(guī)則
    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.
    // 增加對(duì)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.
    // 注冊(cè)默認(rèn)的系統(tǒng)環(huán)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());
    }
}

4、postProcessBeanFactory

該方法是個(gè)空的模板方法。

5、invokeBeanFactoryPostProcessors-->調(diào)用BeanFactoryPostProcessor

BeanFactoryPostProcessor在Spring中非常重要，詳細(xì)分析其調(diào)用過(guò)程。

protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
    //getBeanFactoryPostProcessors->獲取注冊(cè)的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)
    if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
        beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
        beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
    }
}

通過(guò)PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());獲取注冊(cè)的BeanFactoryPostProcessor并調(diào)用。

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

    // Invoke BeanDefinitionRegistryPostProcessors first, if any.
    // 1、首先調(diào)用BeanDefinitionRegistryPostProcessors
    Set<String> processedBeans = new HashSet<>();

    // beanFactory是BeanDefinitionRegistry類型
    if (beanFactory instanceof BeanDefinitionRegistry) {
        BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
        // 定義BeanFactoryPostProcessor
        List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
        // 定義BeanDefinitionRegistryPostProcessor集合
        List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();

        // 循環(huán)手動(dòng)注冊(cè)的beanFactoryPostProcessors
        for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
            // 如果是BeanDefinitionRegistryPostProcessor的實(shí)例話,則調(diào)用其postProcessBeanDefinitionRegistry方法,對(duì)bean進(jìn)行注冊(cè)操作
            if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
                // 如果是BeanDefinitionRegistryPostProcessor類型,則直接調(diào)用其postProcessBeanDefinitionRegistry
                BeanDefinitionRegistryPostProcessor registryProcessor = (BeanDefinitionRegistryPostProcessor) postProcessor;
                registryProcessor.postProcessBeanDefinitionRegistry(registry);
                registryProcessors.add(registryProcessor);
            }
            // 否則則將其當(dāng)做普通的BeanFactoryPostProcessor處理,直接加入regularPostProcessors集合,以備后續(xù)處理
            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.
        // 首先調(diào)用實(shí)現(xiàn)了PriorityOrdered(有限排序接口)的BeanDefinitionRegistryPostProcessors
        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);
        // 調(diào)用所有實(shí)現(xiàn)了PriorityOrdered的的BeanDefinitionRegistryPostProcessors的postProcessBeanDefinitionRegistry方法,注冊(cè)bean
        invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
        // 清空currentRegistryProcessors,以備下次使用
        currentRegistryProcessors.clear();

        // Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
        // 其次,調(diào)用實(shí)現(xiàn)了Ordered(普通排序接口)的BeanDefinitionRegistryPostProcessors
        postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
        for (String ppName : postProcessorNames) {
            if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
                currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                processedBeans.add(ppName);
            }
        }
        // 排序
        sortPostProcessors(currentRegistryProcessors, beanFactory);
        // 加入registryProcessors集合
        registryProcessors.addAll(currentRegistryProcessors);
        // 調(diào)用所有實(shí)現(xiàn)了PriorityOrdered的的BeanDefinitionRegistryPostProcessors的postProcessBeanDefinitionRegistry方法,注冊(cè)bean
        invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
        // 清空currentRegistryProcessors,以備下次使用
        currentRegistryProcessors.clear();

        // Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
        // 最后,調(diào)用其他的BeanDefinitionRegistryPostProcessors
        boolean reiterate = true;
        while (reiterate) {
            reiterate = false;
            postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
            for (String ppName : postProcessorNames) {
                if (!processedBeans.contains(ppName)) {
                    currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                    processedBeans.add(ppName);
                    reiterate = true;
                }
            }
            // 排序
            sortPostProcessors(currentRegistryProcessors, beanFactory);
            // 加入registryProcessors集合
            registryProcessors.addAll(currentRegistryProcessors);
            // 調(diào)用其他的BeanDefinitionRegistryPostProcessors的postProcessBeanDefinitionRegistry方法,注冊(cè)bean
            invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
            // 清空currentRegistryProcessors,以備下次使用
            currentRegistryProcessors.clear();
        }

        // Now, invoke the postProcessBeanFactory callback of all processors handled so far.
        // 調(diào)用所有BeanDefinitionRegistryPostProcessor(包括手動(dòng)注冊(cè)和通過(guò)配置文件注冊(cè))
        // 和BeanFactoryPostProcessor(只有手動(dòng)注冊(cè))的回調(diào)函數(shù)-->postProcessBeanFactory
        invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
        invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
    }

    // 2、如果不是BeanDefinitionRegistry的實(shí)例,那么直接調(diào)用其回調(diào)函數(shù)即可-->postProcessBeanFactory
    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!
    // 3、上面的代碼已經(jīng)處理完了所有的BeanDefinitionRegistryPostProcessors和手動(dòng)注冊(cè)的BeanFactoryPostProcessor
    // 接下來(lái)要處理通過(guò)配置文件注冊(cè)的BeanFactoryPostProcessor
    // 首先獲取所有的BeanFactoryPostProcessor(注意:這里獲取的集合會(huì)包含BeanDefinitionRegistryPostProcessors)
    String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

    // Separate between BeanFactoryPostProcessors that implement PriorityOrdered, Ordered, and the rest.
    // 這里,將實(shí)現(xiàn)了PriorityOrdered,Ordered的處理器和其他的處理器區(qū)分開來(lái),分別進(jìn)行處理
    // PriorityOrdered有序處理器
    List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
    // Ordered有序處理器
    List<String> orderedPostProcessorNames = new ArrayList<>();
    // 無(wú)序處理器
    List<String> nonOrderedPostProcessorNames = new ArrayList<>();
    for (String ppName : postProcessorNames) {
        // 判斷processedBeans是否包含當(dāng)前處理器(processedBeans中的處理器已經(jīng)被處理過(guò));如果包含,則不做任何處理
        if (processedBeans.contains(ppName)) {
            // skip - already processed in first phase above
        }
        else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
            // 加入到PriorityOrdered有序處理器集合
            priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
        }
        else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
            // 加入到Ordered有序處理器集合
            orderedPostProcessorNames.add(ppName);
        }
        else {
            // 加入到無(wú)序處理器集合
            nonOrderedPostProcessorNames.add(ppName);
        }
    }

    // First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
    // 首先調(diào)用實(shí)現(xiàn)了PriorityOrdered接口的處理器
    sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
    invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

    // Next, invoke the BeanFactoryPostProcessors that implement Ordered.
    // 其次,調(diào)用實(shí)現(xiàn)了Ordered接口的處理器
    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.
    // 最后,調(diào)用無(wú)序處理器
    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...
    // 清理元數(shù)據(jù)
    beanFactory.clearMetadataCache();
}

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

    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.
    // 注冊(cè)一個(gè)BeanPostProcessorChecker,它是BeanPostProcessor的子類
    // 用于在BeanPostProcessor實(shí)例化期間創(chuàng)建bean時(shí)記錄信息消息，即當(dāng)bean不符合由所有BeanPostProcessors處理的資格時(shí)。
    int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
    beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

    // Separate between BeanPostProcessors that implement PriorityOrdered, Ordered, and the rest.
    // 對(duì)實(shí)現(xiàn)了PriorityOrdered接口,Ordered接口,內(nèi)部BeanPostProcessor和其他的BeanPostProcessor分類處理
    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.
    // 首先注冊(cè)實(shí)現(xiàn)了PriorityOrdered(有限排序接口)BeanPostProcessor
    sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
    registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

    // Next, register the BeanPostProcessors that implement Ordered.
    // 其次,注冊(cè)實(shí)現(xiàn)了Ordered(排序接口的)BeanPostProcessor
    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.
    // 然后,注冊(cè)無(wú)序的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.
    // 最后,注冊(cè)內(nèi)部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).
    // 注冊(cè)一個(gè)ApplicationListenerDetector用來(lái)偵測(cè)ApplicationListener類型的bean
    // 并將它們加入到容器的applicationEventMulticaster或applicationListeners集合中
    beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}

6、注冊(cè)BeanPostProcessors

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

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

    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.
    // 1、注冊(cè)一個(gè)BeanPostProcessorChecker,它是BeanPostProcessor的子類
    // 用于在BeanPostProcessor實(shí)例化期間創(chuàng)建bean時(shí)記錄信息消息，即當(dāng)bean不符合由所有BeanPostProcessors處理的資格時(shí)。
    int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
    beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

    // Separate between BeanPostProcessors that implement PriorityOrdered, Ordered, and the rest.
    // 2、對(duì)實(shí)現(xiàn)了PriorityOrdered接口,Ordered接口,內(nèi)部BeanPostProcessor和其他的BeanPostProcessor分類處理
    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);
        }
    }

    // 3、注冊(cè)BeanPostProcessors
    // First, register the BeanPostProcessors that implement PriorityOrdered.
    // 首先注冊(cè)實(shí)現(xiàn)了PriorityOrdered(有限排序接口)BeanPostProcessor
    sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
    registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

    // Next, register the BeanPostProcessors that implement Ordered.
    // 其次,注冊(cè)實(shí)現(xiàn)了Ordered(排序接口的)BeanPostProcessor
    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.
    // 然后,注冊(cè)無(wú)序的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.
    // 最后,注冊(cè)內(nèi)部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).
    // 注冊(cè)一個(gè)ApplicationListenerDetector用來(lái)偵測(cè)ApplicationListener類型的bean
    // 并將它們加入到容器的applicationEventMulticaster或applicationListeners集合中
    beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}

7、初始化Message資源

該方法不是很重要，留在以后分析吧。。。

8、初始事件廣播器

protected void initApplicationEventMulticaster() {
    ConfigurableListableBeanFactory beanFactory = getBeanFactory();
    // 1、默認(rèn)使用內(nèi)置的事件廣播器,如果有的話.
    // 我們可以在配置文件中配置Spring事件廣播器或者自定義事件廣播器
    // 例如: <bean id="applicationEventMulticaster" class="org.springframework.context.event.SimpleApplicationEventMulticaster"></bean>
    if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {
        this.applicationEventMulticaster = beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);
    }
    // 2、否則,新建一個(gè)事件廣播器,SimpleApplicationEventMulticaster是spring的默認(rèn)事件廣播器
    else {
        this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory);
        beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, this.applicationEventMulticaster);
    }
}

9、onRefresh-->留給子類初始化其他Bean

該方法是個(gè)空的模板方法

10、注冊(cè)事件監(jiān)聽器

protected void registerListeners() {
    // Register statically specified listeners first.
    // 首先,注冊(cè)指定的靜態(tài)事件監(jiān)聽器,在spring boot中有應(yīng)用
    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!
    // 其次,注冊(cè)普通的事件監(jiān)聽器
    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...
    // 如果有早期事件的話,在這里進(jìn)行事件廣播
    // 因?yàn)榍捌赟impleApplicationEventMulticaster尚未注冊(cè)，無(wú)法發(fā)布事件，
    // 因此早期的事件會(huì)先存放在earlyApplicationEvents集合中，這里把它們?nèi)〕鰜?lái)進(jìn)行發(fā)布
    // 所以早期事件的發(fā)布時(shí)間節(jié)點(diǎn)是早于其他事件的
    Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;
    // 早期事件廣播器是一個(gè)Set<ApplicationEvent>集合,保存了無(wú)法發(fā)布的早期事件,當(dāng)SimpleApplicationEventMulticaster
    // 創(chuàng)建完之后隨即進(jìn)行發(fā)布,同事也要將其保存的事件釋放
    this.earlyApplicationEvents = null;
    if (earlyEventsToProcess != null) {
        for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
            getApplicationEventMulticaster().multicastEvent(earlyEvent);
        }
    }
}

11、初始化其他的單例Bean(非延遲加載的)

protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
    // Initialize conversion service for this context.
    // 判斷有無(wú)ConversionService(bean屬性類型轉(zhuǎn)換服務(wù)接口),并初始化
    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beanFactory中不包含EmbeddedValueResolver,則向其中添加一個(gè)EmbeddedValueResolver
    // EmbeddedValueResolver-->解析bean中的占位符和表達(dá)式
    if (!beanFactory.hasEmbeddedValueResolver()) {
        beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
    }

    // Initialize LoadTimeWeaverAware beans early to allow for registering their transformers early.
    // 初始化LoadTimeWeaverAware類型的bean
    // LoadTimeWeaverAware-->加載Spring Bean時(shí)織入第三方模塊,如AspectJ
    String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
    for (String weaverAwareName : weaverAwareNames) {
        getBean(weaverAwareName);
    }

    // Stop using the temporary ClassLoader for type matching.
    // 釋放臨時(shí)類加載器
    beanFactory.setTempClassLoader(null);

    // Allow for caching all bean definition metadata, not expecting further changes.
    // 凍結(jié)緩存的BeanDefinition元數(shù)據(jù)
    beanFactory.freezeConfiguration();

    // Instantiate all remaining (non-lazy-init) singletons.
    // 初始化其他的非延遲加載的單例bean
    beanFactory.preInstantiateSingletons();
}

12、完成刷新過(guò)程,通知生命周期處理器lifecycleProcessor刷新過(guò)程,同時(shí)發(fā)出ContextRefreshEvent通知

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

    // Initialize lifecycle processor for this context.
    // 初始化生命周期處理器
    initLifecycleProcessor();

    // Propagate refresh to lifecycle processor first.
    // 調(diào)用生命周期處理器的onRefresh方法
    getLifecycleProcessor().onRefresh();

    // Publish the final event.
    // 推送容器刷新事件
    publishEvent(new ContextRefreshedEvent(this));

    // Participate in LiveBeansView MBean, if active.
    // MBean...沒(méi)弄明白
    LiveBeansView.registerApplicationContext(this);
}