26--Sprng ApplicationContext容器re

前面的章节介绍了SpringIoC的基础容器BeanFactory，接下来的章节分析Spring的高级容器ApplicationContext。关于两者的介绍，可以参考以前的章节。接下来我们以ClassPathXmlApplicationContext为例分析ApplicationContext的创建过程。

引、ApplicationContext创建过程简析

/**
 * 创建一个新的ClassPathXmlApplicationContext容器
 * 从指定的xml文件加载BeanDefinition并自动刷新容器
 * @param configLocation 配置文件位置
 * @throws BeansException 容器创建失败，抛出BeansException异常
 */
public ClassPathXmlApplicationContext(String configLocation) throws BeansException {
    this(new String[] {configLocation}, true, null);
}

public ClassPathXmlApplicationContext(String[] configLocations, boolean refresh, @Nullable ApplicationContext parent) throws BeansException {
    // 调用父类构造器
    super(parent);
    // 设定配置文件路径
    setConfigLocations(configLocations);
    if (refresh) {
        // 扩展功能
        refresh();
    }
}

public void refresh() throws BeansException, IllegalStateException {
    synchronized (this.startupShutdownMonitor) {
        // 1、准备刷新上下文环境
        prepareRefresh();
        // 2、读取xml并初始化BeanFactory
        ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
        // 3、填充BeanFactory功能
        prepareBeanFactory(beanFactory);
        try {
            // 4、子类覆盖方法额外处理(空方法)
            postProcessBeanFactory(beanFactory);
            // 5、调动BeanFactoryPostProcessor
            invokeBeanFactoryPostProcessors(beanFactory);
            // 6、注册BeanPostProcessors
            registerBeanPostProcessors(beanFactory);
            // 7、初始化Message资源
            initMessageSource();
            // 8、初始事件广播器
            initApplicationEventMulticaster();
            // 9、留给子类初始化其他Bean(空的模板方法)
            onRefresh();
            // 10、注册事件监听器
            registerListeners();
            // 11、初始化其他的单例Bean(非延迟加载的)
            finishBeanFactoryInitialization(beanFactory);
            // 12、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
            finishRefresh();
        }
        catch (BeansException ex) {
            // 13、销毁已经创建的Bean
            destroyBeans();
            // 14、重置容器激活标签
            cancelRefresh(ex);
            throw ex;
        }
        finally {
            resetCommonCaches();
        }
    }
}

逐步分析refresh()方法。

1、prepareRefresh刷新上下文的准备工作

/**
 * 准备刷新上下文环境，设置它的启动日期和活动标志，以及执行任何属性源的初始化。
 * 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);

    // 在上下文环境中初始化任何占位符属性源。(空的方法,留给子类覆盖)
    initPropertySources();

    // 验证需要的属性文件是否都已放入环境中
    getEnvironment().validateRequiredProperties();

    // 允许收集早期的应用程序事件，一旦有了多播器，就可以发布……
    this.earlyApplicationEvents = new LinkedHashSet<>();
}

2、obtainFreshBeanFactory->读取xml并初始化BeanFactory

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

protected final void refreshBeanFactory() throws BeansException {
    // 1、如果BeanFactory的实例已经存在,则销毁并关闭
    if (hasBeanFactory()) {
        destroyBeans();
        closeBeanFactory();
    }
    // 2、重新创建BeanFactory
    try {
        // 创建BeanFactory
        DefaultListableBeanFactory beanFactory = createBeanFactory();
        // 为BeanFactory设置id
        beanFactory.setSerializationId(getId());
        // 定制beanFactory
        customizeBeanFactory(beanFactory);
        // 加载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);
    }
}

该方法的主要作用就是保证获取一个全新的beanFactory，关于beanFactory我们在前面已经做了很多介绍了，这里不在说明。

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.
    // 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的支持,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,这个主要是对bean的属性等设置管理的一个工具
    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());
    }
}

4、postProcessBeanFactory

该方法是个空的模板方法。

5、invokeBeanFactoryPostProcessors-->调用BeanFactoryPostProcessor

BeanFactoryPostProcessor在Spring中非常重要，详细分析其调用过程。

protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
    //getBeanFactoryPostProcessors->获取注册的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()));
    }
}

通过PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());获取注册的BeanFactoryPostProcessor并调用。

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

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

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

        // 循环手动注册的beanFactoryPostProcessors
        for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
            // 如果是BeanDefinitionRegistryPostProcessor的实例话,则调用其postProcessBeanDefinitionRegistry方法,对bean进行注册操作
            if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
                // 如果是BeanDefinitionRegistryPostProcessor类型,则直接调用其postProcessBeanDefinitionRegistry
                BeanDefinitionRegistryPostProcessor registryProcessor = (BeanDefinitionRegistryPostProcessor) postProcessor;
                registryProcessor.postProcessBeanDefinitionRegistry(registry);
                registryProcessors.add(registryProcessor);
            }
            // 否则则将其当做普通的BeanFactoryPostProcessor处理,直接加入regularPostProcessors集合,以备后续处理
            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.
        // 首先调用实现了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);
        // 调用所有实现了PriorityOrdered的的BeanDefinitionRegistryPostProcessors的postProcessBeanDefinitionRegistry方法,注册bean
        invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
        // 清空currentRegistryProcessors,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);
        // 调用所有实现了PriorityOrdered的的BeanDefinitionRegistryPostProcessors的postProcessBeanDefinitionRegistry方法,注册bean
        invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
        // 清空currentRegistryProcessors,以备下次使用
        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;
            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);
            // 调用其他的BeanDefinitionRegistryPostProcessors的postProcessBeanDefinitionRegistry方法,注册bean
            invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
            // 清空currentRegistryProcessors,以备下次使用
            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);
    }

    // 2、如果不是BeanDefinitionRegistry的实例,那么直接调用其回调函数即可-->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、上面的代码已经处理完了所有的BeanDefinitionRegistryPostProcessors和手动注册的BeanFactoryPostProcessor
    // 接下来要处理通过配置文件注册的BeanFactoryPostProcessor
    // 首先获取所有的BeanFactoryPostProcessor(注意:这里获取的集合会包含BeanDefinitionRegistryPostProcessors)
    String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

    // Separate between BeanFactoryPostProcessors that implement PriorityOrdered, Ordered, and the rest.
    // 这里,将实现了PriorityOrdered,Ordered的处理器和其他的处理器区分开来,分别进行处理
    // PriorityOrdered有序处理器
    List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
    // Ordered有序处理器
    List<String> orderedPostProcessorNames = new ArrayList<>();
    // 无序处理器
    List<String> nonOrderedPostProcessorNames = new ArrayList<>();
    for (String ppName : postProcessorNames) {
        // 判断processedBeans是否包含当前处理器(processedBeans中的处理器已经被处理过);如果包含,则不做任何处理
        if (processedBeans.contains(ppName)) {
            // skip - already processed in first phase above
        }
        else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
            // 加入到PriorityOrdered有序处理器集合
            priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
        }
        else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
            // 加入到Ordered有序处理器集合
            orderedPostProcessorNames.add(ppName);
        }
        else {
            // 加入到无序处理器集合
            nonOrderedPostProcessorNames.add(ppName);
        }
    }

    // First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
    // 首先调用实现了PriorityOrdered接口的处理器
    sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
    invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

    // Next, invoke the BeanFactoryPostProcessors that implement Ordered.
    // 其次,调用实现了Ordered接口的处理器
    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,调用无序处理器
    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...
    // 清理元数据
    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.
    // 注册一个BeanPostProcessorChecker,它是BeanPostProcessor的子类
    // 用于在BeanPostProcessor实例化期间创建bean时记录信息消息，即当bean不符合由所有BeanPostProcessors处理的资格时。
    int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
    beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

    // Separate between BeanPostProcessors that implement PriorityOrdered, Ordered, and the rest.
    // 对实现了PriorityOrdered接口,Ordered接口,内部BeanPostProcessor和其他的BeanPostProcessor分类处理
    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.
    // 首先注册实现了PriorityOrdered(有限排序接口)BeanPostProcessor
    sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
    registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

    // Next, register the BeanPostProcessors that implement Ordered.
    // 其次,注册实现了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,注册无序的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,注册内部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).
    // 注册一个ApplicationListenerDetector用来侦测ApplicationListener类型的bean
    // 并将它们加入到容器的applicationEventMulticaster或applicationListeners集合中
    beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}

6、注册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、注册一个BeanPostProcessorChecker,它是BeanPostProcessor的子类
    // 用于在BeanPostProcessor实例化期间创建bean时记录信息消息，即当bean不符合由所有BeanPostProcessors处理的资格时。
    int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
    beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

    // Separate between BeanPostProcessors that implement PriorityOrdered, Ordered, and the rest.
    // 2、对实现了PriorityOrdered接口,Ordered接口,内部BeanPostProcessor和其他的BeanPostProcessor分类处理
    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、注册BeanPostProcessors
    // First, register the BeanPostProcessors that implement PriorityOrdered.
    // 首先注册实现了PriorityOrdered(有限排序接口)BeanPostProcessor
    sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
    registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

    // Next, register the BeanPostProcessors that implement Ordered.
    // 其次,注册实现了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,注册无序的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,注册内部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).
    // 注册一个ApplicationListenerDetector用来侦测ApplicationListener类型的bean
    // 并将它们加入到容器的applicationEventMulticaster或applicationListeners集合中
    beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}

7、初始化Message资源

该方法不是很重要，留在以后分析吧。。。

8、初始事件广播器

protected void initApplicationEventMulticaster() {
    ConfigurableListableBeanFactory beanFactory = getBeanFactory();
    // 1、默认使用内置的事件广播器,如果有的话.
    // 我们可以在配置文件中配置Spring事件广播器或者自定义事件广播器
    // 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、否则,新建一个事件广播器,SimpleApplicationEventMulticaster是spring的默认事件广播器
    else {
        this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory);
        beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, this.applicationEventMulticaster);
    }
}

9、onRefresh-->留给子类初始化其他Bean

该方法是个空的模板方法

10、注册事件监听器

protected void registerListeners() {
    // Register statically specified listeners first.
    // 首先,注册指定的静态事件监听器,在spring boot中有应用
    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,注册普通的事件监听器
    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...
    // 如果有早期事件的话,在这里进行事件广播
    // 因为前期SimpleApplicationEventMulticaster尚未注册，无法发布事件，
    // 因此早期的事件会先存放在earlyApplicationEvents集合中，这里把它们取出来进行发布
    // 所以早期事件的发布时间节点是早于其他事件的
    Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;
    // 早期事件广播器是一个Set<ApplicationEvent>集合,保存了无法发布的早期事件,当SimpleApplicationEventMulticaster
    // 创建完之后随即进行发布,同事也要将其保存的事件释放
    this.earlyApplicationEvents = null;
    if (earlyEventsToProcess != null) {
        for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
            getApplicationEventMulticaster().multicastEvent(earlyEvent);
        }
    }
}

11、初始化其他的单例Bean(非延迟加载的)

protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
    // Initialize conversion service for this context.
    // 判断有无ConversionService(bean属性类型转换服务接口),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,则向其中添加一个EmbeddedValueResolver
    // EmbeddedValueResolver-->解析bean中的占位符和表达式
    if (!beanFactory.hasEmbeddedValueResolver()) {
        beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
    }

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

    // Stop using the temporary ClassLoader for type matching.
    // 释放临时类加载器
    beanFactory.setTempClassLoader(null);

    // Allow for caching all bean definition metadata, not expecting further changes.
    // 冻结缓存的BeanDefinition元数据
    beanFactory.freezeConfiguration();

    // Instantiate all remaining (non-lazy-init) singletons.
    // 初始化其他的非延迟加载的单例bean
    beanFactory.preInstantiateSingletons();
}

12、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

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

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

    // Propagate refresh to lifecycle processor first.
    // 调用生命周期处理器的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...没弄明白
    LiveBeansView.registerApplicationContext(this);
}