文章

深入分析ApplicationContext的refresh()方法

发表于 更新于
作者 deathwhispers
23 分钟阅读

本文主要基于 Spring 5.0.6.RELEASE

摘要: 原创出处http://cmsblogs.com/?p=todo「小明哥」，谢谢！

上篇博客只是对 <font style="color:rgb(51, 51, 51);">ApplicationContext</font> 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 <font style="color:rgb(51, 51, 51);">ApplicationContext</font> 最重要的方法（小编认为的） ：#refresh()方法。

艿艿：我也这么认为，<font style="color:rgb(51, 51, 51);">#refresh()</font>方法是关键的关键！

<font style="color:rgb(51, 51, 51);">#refresh()</font>方法，是定义在 <font style="color:rgb(51, 51, 51);">ConfigurableApplicationContext</font> 类中的，如下：

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// ConfigurableApplicationContext.java
/** * 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 <font style="color:rgb(51, 51, 51);">AbstractApplicationContext</font> 中实现。如下：

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// AbstractApplicationContext.java
@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。

1. 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

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// AbstractApplicationContext.java
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 <font style="color:rgb(51, 51, 51);">context</font> 启动时间
  2. 设置 <font style="color:rgb(51, 51, 51);">context</font> 的当前状态
  3. 初始化 <font style="color:rgb(51, 51, 51);">context environment</font> 中占位符
  4. 对属性进行必要的验证

2. obtainFreshBeanFactory()

创建并初始化 <font style="color:rgb(51, 51, 51);">BeanFactory</font>

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// AbstractApplicationContext.java
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<font style="color:rgb(51, 51, 51);">#refreshBeanFactory()</font>方法，该方法的核心任务就是创建 <font style="color:rgb(51, 51, 51);">BeanFactory</font> 并对其就行一番初始化。如下：

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// AbstractRefreshableApplicationContext.java
@Override
protected final void refreshBeanFactory() throws BeansException {
    // 若已有 BeanFactory ，销毁它的 Bean 们，并销毁 BeanFactory
    if (hasBeanFactory()) {
        destroyBeans();
        closeBeanFactory();
    }
    try {
        // 创建 BeanFactory 对象        DefaultListableBeanFactory beanFactory = createBeanFactory();
        // 指定序列化编号        beanFactory.setSerializationId(getId());
        // 定制 BeanFactory 设置相关属性        customizeBeanFactory(beanFactory);
        // 加载
        BeanDefinition 们        loadBeanDefinitions(beanFactory); // 设置 Context 的
        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 <font style="color:rgb(51, 51, 51);">BeanFactory</font> ，如果存在则对其进行销毁和关闭
  2. 调用<font style="color:rgb(51, 51, 51);">#createBeanFactory()</font><font style="color:rgb(51, 51, 51);">BeanFactory</font><font style="color:rgb(51, 51, 51);">DefaultListableBeanFactory</font> 方法，创建一个 实例，其实就是 。
  3. 自定义 <font style="color:rgb(51, 51, 51);">BeanFactory</font>
  4. 加载 <font style="color:rgb(51, 51, 51);">BeanDefinition</font> 。
  5. 将创建好的 <font style="color:rgb(51, 51, 51);">bean</font><font style="color:rgb(51, 51, 51);">context</font> 工厂的引用交给的 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 <font style="color:rgb(51, 51, 51);">BeanDefinition</font>。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<font style="color:rgb(51, 51, 51);">BeanDefinitionReader#loadBeanDefinitions(Resource resource)</font>方法，作为入口来分析的，示例如下：

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// 示例代码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BeanDefinitionReader#loadBeanDefinitions(Resource)方法，是定义在 BeanDefinitionReader 中，而此处的#loadBeanDefinitions(DefaultListableBeanFactory beanFactory)则是定义在 AbstractRefreshableApplicationContext 中，如下：

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// AbstractRefreshableApplicationContext.java
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：

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// AbstractXmlApplicationContext.java
@Override
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
    // Create a
    new XmlBeanDefinitionReader for the given
    BeanFactory.    // 创建 XmlBeanDefinitionReader 对象    XmlBeanDefinitionReader beanDefinitionReader =
    new XmlBeanDefinitionReader(beanFactory); // Configure the bean definition reader with
    this context's    // resource loading environment.    // 对 XmlBeanDefinitionReader 进行环境变量的设置    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.    // 对 XmlBeanDefinitionReader 进行设置，可以进行覆盖    initBeanDefinitionReader(beanDefinitionReader);    // 从
    Resource 们中，加载 BeanDefinition 们    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。代码如下：
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// AbstractXmlApplicationContext.java
protected
void loadBeanDefinitions(XmlBeanDefinitionReader reader)
throws BeansException,
IOException {
    // 从配置文件 Resource 中，加载
    BeanDefinition 们
    Resource[] configResources = getConfigResources();
    if (configResources != null) {
        reader.loadBeanDefinitions(configResources);
    } // 从配置文件地址中，加载
    BeanDefinition 们
    String[] configLocations = getConfigLocations();
    if (configLocations != null) {
        reader.loadBeanDefinitions(configLocations);
    }
}

```plain text

  • 到这里我们发现，其实内部依然是调用

    <font style="color:rgb(51, 51, 51);">BeanDefinitionReader#loadBeanDefinitionn()</font>进行 <font style="color:rgb(51, 51, 51);">BeanDefinition</font> 的加载进程。 ```

3. prepareBeanFactory(beanFactory)

填充 BeanFactory 功能

上面获取获取的 <font style="color:rgb(51, 51, 51);">BeanFactory</font> 除了加载了一些 <font style="color:rgb(51, 51, 51);">BeanDefinition</font> 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 <font style="color:rgb(51, 51, 51);">context</font>的 <font style="color:rgb(51, 51, 51);">ClassLoader</font> 和 后置处理器等等。

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// AbstractApplicationContext.java
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 <font style="color:rgb(51, 51, 51);">BeanFactory</font> 设置各种各种的功能。

4. postProcessBeanFactory()

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

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// AbstractApplicationContext.java
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 <font style="color:rgb(51, 51, 51);">ServletContextAwareProcessor</font><font style="color:rgb(51, 51, 51);">BeanFactory</font><font style="color:rgb(51, 51, 51);">processor</font><font style="color:rgb(51, 51, 51);">BeanPostProcessor</font><font style="color:rgb(51, 51, 51);">ServletContext</font><font style="color:rgb(51, 51, 51);">ServletContextAware</font><font style="color:rgb(51, 51, 51);">bean</font> 到 容器中，该 实现 接口，主要用于将 传递给实现了 接口的
  2. 忽略 <font style="color:rgb(51, 51, 51);">ServletContextAware</font><font style="color:rgb(51, 51, 51);">ServletConfigAware</font> 、
  3. 注册 WEB 应用特定的域（scope）到 <font style="color:rgb(51, 51, 51);">beanFactory</font><font style="color:rgb(51, 51, 51);">WebApplicationContext</font> 中，以便 可以使用它们。比如 “request” , “session” , “globalSession” , “application”
  4. 注册 WEB 应用特定的 Environment bean 到 <font style="color:rgb(51, 51, 51);">beanFactory</font><font style="color:rgb(51, 51, 51);">WebApplicationContext</font> 中，以便 可以使用它们。如：”contextParameters”, “contextAttributes”

5. invokeBeanFactoryPostProcessors()

激活各种BeanFactory处理器

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// AbstractApplicationContext.java
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。

6. 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。

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// AbstractApplicationContext.java
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));
}

7. 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。

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// AbstractApplicationContext.java
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 + "]");        }    }}

8. initApplicationEventMulticaster

初始化上下文事件广播器

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// AbstractApplicationContext.java
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。

9. 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。

10. registerListeners

在所有 bean 中查找 listener bean，然后注册到广播器中

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// AbstractApplicationContext.java
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);
        }
    }
}

10. finishBeanFactoryInitialization

初始化剩下的单例Bean(非延迟加载的)

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// AbstractApplicationContext.java
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();
}

11. finishRefresh

完成刷新过程,通知生命周期处理器 <font style="color:rgb(0, 0, 0);">lifecycleProcessor</font> 刷新过程,同时发出 <font style="color:rgb(0, 0, 0);">ContextRefreshEvent</font> 通知别人

主要是调用<font style="color:rgb(51, 51, 51);">LifecycleProcessor#onRefresh()</font>，并且发布事件（<font style="color:rgb(0, 0, 0);">ContextRefreshedEvent</font>）。

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// AbstractApplicationContext.java
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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