2022-08-23  阅读(665)
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上篇博客只是对 ApplicationContext 相关的接口做了一个简单的介绍,作为一个高富帅级别的 Spring 容器,它涉及的方法实在是太多了,全部介绍是不可能的,而且大部分功能都已经在前面系列博客中做了详细的介绍,所以这篇博问介绍 ApplicationContext 最重要的方法(小编认为的) :refresh()

refresh() 是定义在 ConfigurableApplicationContext 类中的,如下:

                /**
                 * Load or refresh the persistent representation of the configuration,
                 * which might an XML file, properties file, or relational database schema.
                 * As this is a startup method, it should destroy already created singletons
                 * if it fails, to avoid dangling resources. In other words, after invocation
                 * of that method, either all or no singletons at all should be instantiated.
                 * @throws BeansException if the bean factory could not be initialized
                 * @throws IllegalStateException if already initialized and multiple refresh
                 * attempts are not supported
                 */
                void refresh() throws BeansException, IllegalStateException;

作用就是: 刷新 Spring 的应用上下文 。其实现是在 AbstractApplicationContext 中实现。如下:

                @Override
                public void refresh() throws BeansException, IllegalStateException {
                    synchronized (this.startupShutdownMonitor) {
                        // 准备刷新上下文环境
                        prepareRefresh();
            
                        // 创建并初始化 BeanFactory
                        ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
            
                        // 填充BeanFactory功能
                        prepareBeanFactory(beanFactory);
            
                        try {
                            // 提供子类覆盖的额外处理,即子类处理自定义的BeanFactoryPostProcess
                            postProcessBeanFactory(beanFactory);
            
                            // 激活各种BeanFactory处理器
                            invokeBeanFactoryPostProcessors(beanFactory);
            
                            // 注册拦截Bean创建的Bean处理器,即注册 BeanPostProcessor
                            registerBeanPostProcessors(beanFactory);
            
                            // 初始化上下文中的资源文件,如国际化文件的处理等
                            initMessageSource();
            
                            // 初始化上下文事件广播器
                            initApplicationEventMulticaster();
            
                            // 给子类扩展初始化其他Bean
                            onRefresh();
            
                            // 在所有bean中查找listener bean,然后注册到广播器中
                            registerListeners();
            
                            // 初始化剩下的单例Bean(非延迟加载的)
                            finishBeanFactoryInitialization(beanFactory);
            
                            // 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
                            finishRefresh();
                        }
            
                        catch (BeansException ex) {
                            if (logger.isWarnEnabled()) {
                                logger.warn("Exception encountered during context initialization - " +
                                        "cancelling refresh attempt: " + ex);
                            }
            
                            //  销毁已经创建的Bean
                            destroyBeans();
            
                            // 重置容器激活标签
                            cancelRefresh(ex);
            
                            // 抛出异常
                            throw ex;
                        }
            
                        finally {
                            // Reset common introspection caches in Spring's core, since we
                            // might not ever need metadata for singleton beans anymore...
                            resetCommonCaches();
                        }
                    }
                }

这里每一个方法都非常重要,需要一个一个地解释说明。

prepareRefresh()

初始化上下文环境,对系统的环境变量或者系统属性进行准备和校验,如环境变量中必须设置某个值才能运行,否则不能运行,这个时候可以在这里加这个校验,重写initPropertySources方法就好了

                protected void prepareRefresh() {
                   // 设置启动日期
                    this.startupDate = System.currentTimeMillis();
                    // 设置 context 当前状态
                    this.closed.set(false);
                    this.active.set(true);
            
                    if (logger.isInfoEnabled()) {
                        logger.info("Refreshing " + this);
                    }
            
                    // 初始化context environment(上下文环境)中的占位符属性来源
                    initPropertySources();
            
                    // 对属性进行必要的验证
                    getEnvironment().validateRequiredProperties();
            
                    this.earlyApplicationEvents = new LinkedHashSet<>();
                }

该方法主要是做一些准备工作,如:

  1. 设置 context 启动时间
  2. 设置 context 的当前状态
  3. 初始化 context environment 中占位符
  4. 对属性进行必要的验证

obtainFreshBeanFactory()

创建并初始化 BeanFactory

                protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
                   // 刷新 BeanFactory
                    refreshBeanFactory();
                    // 获取 BeanFactory
                    ConfigurableListableBeanFactory beanFactory = getBeanFactory();
                    if (logger.isDebugEnabled()) {
                        logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
                    }
                    return beanFactory;
                }

核心方法就在 refreshBeanFactory() ,该方法的核心任务就是创建 BeanFactory 并对其就行一番初始化。如下:

                protected final void refreshBeanFactory() throws BeansException {
                    if (hasBeanFactory()) {
                        destroyBeans();
                        closeBeanFactory();
                    }
                    try {
                        DefaultListableBeanFactory beanFactory = createBeanFactory();
                        beanFactory.setSerializationId(getId());
                        customizeBeanFactory(beanFactory);
                        loadBeanDefinitions(beanFactory);
                        synchronized (this.beanFactoryMonitor) {
                            this.beanFactory = beanFactory;
                        }
                    }
                    catch (IOException ex) {
                        throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
                    }
                }
  1. 判断当前容器是否存在一个 BeanFactory,如果存在则对其进行销毁和关闭
  2. 调用 createBeanFactory() 创建一个 BeanFactory 实例,其实就是 DefaultListableBeanFactory
  3. 自定义 BeanFactory
  4. 加载 BeanDefinition
  5. 将创建好的 bean 工厂的引用交给的 context 来管理

上面 5 个步骤,都是比较简单的,但是有必要讲解下第 4 步:加载 BeanDefinition。如果各位看过 【死磕 Spring】系列的话,在刚刚开始分析源码的时候,小编就是以 loadBeanDefinitions() 为入口来分析的,如下:

            ClassPathResource resource = new ClassPathResource("bean.xml");
            DefaultListableBeanFactory factory = new DefaultListableBeanFactory();
            XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(factory);
            reader.loadBeanDefinitions(resource);

只不过这段代码的 loadBeanDefinitions() 是定义在 BeanDefinitionReader 中,而此处的 loadBeanDefinitions() 则是定义在 AbstractRefreshableApplicationContext 中,如下:

                protected abstract void loadBeanDefinitions(DefaultListableBeanFactory beanFactory)
                        throws BeansException, IOException

由具体的子类实现,我们以 AbstractXmlApplicationContext 为例,实现如下:

                protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
                    // Create a new XmlBeanDefinitionReader for the given BeanFactory.
                    XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
            
                    // Configure the bean definition reader with this context's
                    // resource loading environment.
                    beanDefinitionReader.setEnvironment(this.getEnvironment());
                    beanDefinitionReader.setResourceLoader(this);
                    beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));
            
                    // Allow a subclass to provide custom initialization of the reader,
                    // then proceed with actually loading the bean definitions.
                    initBeanDefinitionReader(beanDefinitionReader);
                    loadBeanDefinitions(beanDefinitionReader);
                }

新建 XmlBeanDefinitionReader 实例对象 beanDefinitionReader,调用 initBeanDefinitionReader() 对其进行初始化,然后调用 loadBeanDefinitions() 加载 BeanDefinition。

                protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {
                    Resource[] configResources = getConfigResources();
                    if (configResources != null) {
                        reader.loadBeanDefinitions(configResources);
                    }
                    String[] configLocations = getConfigLocations();
                    if (configLocations != null) {
                        reader.loadBeanDefinitions(configLocations);
                    }
                }

到这里我们发现,其实内部依然是调用 BeanDefinitionReader#loadBeanDefinitionn() 进行 BeanDefinition 的加载进程。

prepareBeanFactory(beanFactory)

填充 BeanFactory 功能

上面获取获取的 BeanFactory 除了加载了一些 BeanDefinition 就没有其他任何东西了,这个时候其实还不能投入生产,因为还少配置了一些东西,比如 context的 ClassLoader 和 后置处理器等等。

                protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
                    // 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
                    beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));
            
                    // 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);
            
                    // 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));
            
                    // 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()));
                    }
            
                    // 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());
                    }
                }

看上面的源码知道这个就是对 BeanFactory 设置各种各种的功能。

postProcessBeanFactory()

提供子类覆盖的额外处理,即子类处理自定义的BeanFactoryPostProcess

                protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
                    beanFactory.addBeanPostProcessor(new ServletContextAwareProcessor(this.servletContext, this.servletConfig));
                    beanFactory.ignoreDependencyInterface(ServletContextAware.class);
                    beanFactory.ignoreDependencyInterface(ServletConfigAware.class);
            
                    WebApplicationContextUtils.registerWebApplicationScopes(beanFactory, this.servletContext);
                    WebApplicationContextUtils.registerEnvironmentBeans(beanFactory, this.servletContext, this.servletConfig);
                }
  1. 添加 ServletContextAwareProcessor 到 BeanFactory 容器中,该 processor 实现 BeanPostProcessor 接口,主要用于将ServletContext 传递给实现了 ServletContextAware 接口的 bean
  2. 忽略 ServletContextAware、ServletConfigAware
  3. 注册 WEB 应用特定的域(scope)到 beanFactory 中,以便 WebApplicationContext 可以使用它们。比如 "request" , "session" , "globalSession" , "application"
  4. 注册 WEB 应用特定的 Environment bean 到 beanFactory 中,以便WebApplicationContext 可以使用它们。如:"contextParameters", "contextAttributes"

invokeBeanFactoryPostProcessors()

激活各种BeanFactory处理器

                public static void invokeBeanFactoryPostProcessors(
                        ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
            
                    // 定义一个 set 保存所有的 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<>();
            
                        // 迭代注册的 beanFactoryPostProcessors
                        for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
                            // 如果是 BeanDefinitionRegistryPostProcessor,则调用 postProcessBeanDefinitionRegistry 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 集合中即可,便于后面做后续处理
                                regularPostProcessors.add(postProcessor);
                            }
                        }
            
                        // 用于保存当前处理的 BeanDefinitionRegistryPostProcessor
                        List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();
            
                        // 首先处理实现了 PriorityOrdered (有限排序接口)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 BeanDefinitionRegistryPostProcessors 的 postProcessBeanDefinitionRegistry()
                        invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
            
                        // 清空,以备下次使用
                        currentRegistryProcessors.clear();
            
                        // 其次,调用是实现了 Ordered(普通排序接口)的 BeanDefinitionRegistryPostProcessors
                        // 逻辑和 上面一样
                        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();
            
                        // 最后调用其他的 BeanDefinitionRegistryPostProcessors
                        boolean reiterate = true;
                        while (reiterate) {
                            reiterate = false;
                            // 获取 BeanDefinitionRegistryPostProcessor
                            postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
                            for (String ppName : postProcessorNames) {
            
                                // 没有包含在 processedBeans 中的(因为包含了的都已经处理了)
                                if (!processedBeans.contains(ppName)) {
                                    currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                                    processedBeans.add(ppName);
                                    reiterate = true;
                                }
                            }
            
                            // 与上面处理逻辑一致
                            sortPostProcessors(currentRegistryProcessors, beanFactory);
                            registryProcessors.addAll(currentRegistryProcessors);
                            invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
                            currentRegistryProcessors.clear();
                        }
            
                        // 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 只需要调用其回调函数(postProcessBeanFactory())即可
                        invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
                    }
            
                    //
                    String[] postProcessorNames =
                            beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);
            
                    // 这里同样需要区分 PriorityOrdered 、Ordered 和 no Ordered
                    List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
                    List<String> orderedPostProcessorNames = new ArrayList<>();
                    List<String> nonOrderedPostProcessorNames = new ArrayList<>();
                    for (String ppName : postProcessorNames) {
                        // 已经处理过了的,跳过
                        if (processedBeans.contains(ppName)) {
                            // skip - already processed in first phase above
                        }
                        // PriorityOrdered
                        else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
                            priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
                        }
                        // Ordered
                        else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
                            orderedPostProcessorNames.add(ppName);
                        }
                        // no Ordered
                        else {
                            nonOrderedPostProcessorNames.add(ppName);
                        }
                    }
            
                    // First, PriorityOrdered 接口
                    sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
                    invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);
            
                    // Next, Ordered 接口
                    List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>();
                    for (String postProcessorName : orderedPostProcessorNames) {
                        orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
                    }
                    sortPostProcessors(orderedPostProcessors, beanFactory);
                    invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);
            
                    // Finally, no ordered
                    List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>();
                    for (String postProcessorName : nonOrderedPostProcessorNames) {
                        nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
                    }
                    invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);
            
                    // Clear cached merged bean definitions since the post-processors might have
                    // modified the original metadata, e.g. replacing placeholders in values...
                    beanFactory.clearMetadataCache();
                }

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、no ordered 三种方式分开处理、调用。

registerBeanPostProcessors

注册拦截Bean创建的Bean处理器,即注册 BeanPostProcessor

与 BeanFactoryPostProcessor 一样,也是委托给 PostProcessorRegistrationDelegate 来实现的。

                public static void registerBeanPostProcessors(
                        ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
            
                    // 所有的 BeanPostProcessors
                    String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);
            
                    // 注册 BeanPostProcessorChecker
                    // 主要用于记录一些 bean 的信息,这些 bean 不符合所有 BeanPostProcessors 处理的资格时
                    int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
                    beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));
            
                    // 区分 PriorityOrdered、Ordered 、 no ordered
                    List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
                    List<String> orderedPostProcessorNames = new ArrayList<>();
                    List<String> nonOrderedPostProcessorNames = new ArrayList<>();
                    // MergedBeanDefinition
                    List<BeanPostProcessor> internalPostProcessors = 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, PriorityOrdered
                    sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
                    registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);
            
                    // Next, Ordered
                    List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>();
                    for (String ppName : orderedPostProcessorNames) {
                        BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
                        orderedPostProcessors.add(pp);
                        if (pp instanceof MergedBeanDefinitionPostProcessor) {
                            internalPostProcessors.add(pp);
                        }
                    }
                    sortPostProcessors(orderedPostProcessors, beanFactory);
                    registerBeanPostProcessors(beanFactory, orderedPostProcessors);
            
                    // onOrdered
                    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, all internal BeanPostProcessors.
                    sortPostProcessors(internalPostProcessors, beanFactory);
                    registerBeanPostProcessors(beanFactory, internalPostProcessors);
            
                    // 重新注册用来自动探测内部ApplicationListener的post-processor,这样可以将他们移到处理器链条的末尾
                    beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
                }

initMessageSource

初始化上下文中的资源文件,如国际化文件的处理等

其实该方法就是初始化一个 MessageSource 接口的实现类,主要用于国际化/i18n。

                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);
                        // 如果有父类
                        // HierarchicalMessageSource 分级处理的 MessageSource
                        if (this.parent != null && this.messageSource instanceof HierarchicalMessageSource) {
                            HierarchicalMessageSource hms = (HierarchicalMessageSource) this.messageSource;
                            if (hms.getParentMessageSource() == null) {
                                // 如果没有注册父 MessageSource,则设置为父类上下文的的 MessageSource
                                hms.setParentMessageSource(getInternalParentMessageSource());
                            }
                        }
                        if (logger.isDebugEnabled()) {
                            logger.debug("Using MessageSource [" + this.messageSource + "]");
                        }
                    }
                    else {
                        // 使用 空 MessageSource
                        DelegatingMessageSource dms = new DelegatingMessageSource();
                        dms.setParentMessageSource(getInternalParentMessageSource());
                        this.messageSource = dms;
                        beanFactory.registerSingleton(MESSAGE_SOURCE_BEAN_NAME, this.messageSource);
                        if (logger.isDebugEnabled()) {
                            logger.debug("Unable to locate MessageSource with name '" + MESSAGE_SOURCE_BEAN_NAME +
                                    "': using default [" + this.messageSource + "]");
                        }
                    }
                }

initApplicationEventMulticaster

初始化上下文事件广播器

                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.isDebugEnabled()) {
                            logger.debug("Using ApplicationEventMulticaster [" + this.applicationEventMulticaster + "]");
                        }
                    }
                    else {
                        // 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.isDebugEnabled()) {
                            logger.debug("Unable to locate ApplicationEventMulticaster with name '" +
                                    APPLICATION_EVENT_MULTICASTER_BEAN_NAME +
                                    "': using default [" + this.applicationEventMulticaster + "]");
                        }
                    }
                }

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。

onRefresh

给子类扩展初始化其他Bean

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。

registerListeners

在所有 bean 中查找 listener bean,然后注册到广播器中

                protected void registerListeners() {
                    // 注册静态 监听器
                    for (ApplicationListener<?> listener : getApplicationListeners()) {
                        getApplicationEventMulticaster().addApplicationListener(listener);
                    }
            
                    String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);
                    for (String listenerBeanName : listenerBeanNames) {
                        getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);
                    }
            
                    // 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);
                        }
                    }
                }

finishBeanFactoryInitialization

初始化剩下的单例Bean(非延迟加载的)

                protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
                    // 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));
                    }
            
                    // 如果之前没有注册 bean 后置处理器(例如PropertyPlaceholderConfigurer),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);
                    }
            
                    // 停止使用临时的 ClassLoader
                    beanFactory.setTempClassLoader(null);
            
                    //
                    beanFactory.freezeConfiguration();
            
                    // 初始化所有剩余的单例(非延迟初始化)
                    beanFactory.preInstantiateSingletons();
                }

finishRefresh

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

主要是调用 LifecycleProcessor#onRefresh() ,并且发布事件(ContextRefreshedEvent)。

                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);
                }
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