【07】Spring源码-分析篇-refresh方法

Spring初始化源码分析

  接下来我们详细分析下refresh方法的作用。

一、refresh方法

@Override
  public void refresh() throws BeansException, IllegalStateException {
    synchronized (this.startupShutdownMonitor) {
        // 1.context 为刷新做准备
      // Prepare this context for refreshing.
      prepareRefresh();

      // Tell the subclass to refresh the internal bean factory.
      // 2.让子类实现刷新内部持有BeanFactory
      ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

      // Prepare the bean factory for use in this context.
      // 3.对beanFactory做一些准备工作：注册一些context回调、bean等
      prepareBeanFactory(beanFactory);

      try {
        // Allows post-processing of the bean factory in context subclasses.
        // 4.调用留给子类来提供实现逻辑的 对BeanFactory进行处理的钩子方法
        postProcessBeanFactory(beanFactory);

        // Invoke factory processors registered as beans in the context.
        // 5.执行context中注册的 BeanFactoryPostProcessor bean
        invokeBeanFactoryPostProcessors(beanFactory);

        // Register bean processors that intercept bean creation.
        // 6.注册BeanPostProcessor: 获得用户注册的BeanPostProcessor实例，注册到BeanFactory上
        registerBeanPostProcessors(beanFactory);

        // Initialize message source for this context.
        // 7.初始化国际化资源
        initMessageSource();

        // Initialize event multicaster for this context.
        // 8.初始化Application event 广播器
        initApplicationEventMulticaster();

        // Initialize other special beans in specific context subclasses.
        // 9.执行 有子类来提供实现逻辑的钩子方法 onRefresh
        onRefresh();

        // Check for listener beans and register them.
        // 10.注册ApplicationListener: 获得用户注册的ApplicationListener Bean实例，注册到广播器上
        registerListeners();

        // Instantiate all remaining (non-lazy-init) singletons.
        // 11、完成剩余的单例Bean的实例化
        finishBeanFactoryInitialization(beanFactory);

        // Last step: publish corresponding event.
        // 12 发布对应的事件
        finishRefresh();
      }

      catch (BeansException ex) {
        if (logger.isWarnEnabled()) {
          logger.warn("Exception encountered during context initialization - " +
              "cancelling refresh attempt: " + ex);
        }

        // Destroy already created singletons to avoid dangling resources.
        destroyBeans();

        // Reset 'active' flag.
        cancelRefresh(ex);

        // Propagate exception to caller.
        throw ex;
      }

      finally {
        // Reset common introspection caches in Spring's core, since we
        // might not ever need metadata for singleton beans anymore...
        resetCommonCaches();
      }
    }
  }

二、prepareRefresh

  完成一些刷新前的准备工作.

protected void prepareRefresh() {
    // Switch to active.
    this.startupDate = System.currentTimeMillis();
// 设置相关的状态
    this.closed.set(false);
    this.active.set(true);

    if (logger.isDebugEnabled()) {
      if (logger.isTraceEnabled()) {
        logger.trace("Refreshing " + this);
      }
      else {
        logger.debug("Refreshing " + getDisplayName());
      }
    }

    // Initialize any placeholder property sources in the context environment.
    initPropertySources();

    // Validate that all properties marked as required are resolvable:
    // see ConfigurablePropertyResolver#setRequiredProperties
    getEnvironment().validateRequiredProperties();

    // Store pre-refresh ApplicationListeners...
    if (this.earlyApplicationListeners == null) {
      this.earlyApplicationListeners = new LinkedHashSet<>(this.applicationListeners);
    }
    else {
      // Reset local application listeners to pre-refresh state.
      this.applicationListeners.clear();
      this.applicationListeners.addAll(this.earlyApplicationListeners);
    }

    // Allow for the collection of early ApplicationEvents,
    // to be published once the multicaster is available...
    this.earlyApplicationEvents = new LinkedHashSet<>();
  }

三、obtainFreshBeanFactory

  在obtainFreshBeanFactory方法会完成BeanFactory对象的创建。

  protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
    // 刷新容器
    refreshBeanFactory();
    return getBeanFactory();
  }

如果是基于XML的方式使用会在refreshBeanFactory中完成配置文件的加载解析操作

@Override
  protected final void refreshBeanFactory() throws BeansException {
    if (hasBeanFactory()) {
            // 销毁前面的 BeanFactory
      destroyBeans();
      closeBeanFactory();
    }
    try {
      // 创建 BeanFactory 对象
      DefaultListableBeanFactory beanFactory = createBeanFactory();
      beanFactory.setSerializationId(getId());
      customizeBeanFactory(beanFactory);
      loadBeanDefinitions(beanFactory); // 加载解析配置文件
      this.beanFactory = beanFactory;
    }
    catch (IOException ex) {
      throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
    }
  }

四、prepareBeanFactory

  上面的obtainFreshBeanFactory中完成了BeanFactory的创建和相关BeanDefinition对象的组装，然后在接下来的prepareBeanFactory中会完成相关的准备工作。

protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
    // Tell the internal bean factory to use the context's class loader etc.
    // 设置beanFactory的classloader为当前context的classloader
    beanFactory.setBeanClassLoader(getClassLoader());
    // 设置beanfactory的表达式语言处理器
    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类
    beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));

    // Configure the bean factory with context callbacks.
    // 添加beanPostProcessor,ApplicationContextAwareProcessor此类用来完成某些Aware对象的注入
    beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
    // 设置要忽略自动装配的接口，很多同学理解不了为什么此处要对这些接口进行忽略，原因非常简单，这些接口的实现是由容器通过set方法进行注入的，
    // 所以在使用autowire进行注入的时候需要将这些接口进行忽略
    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,当在进行ioc初始化的如果有多个实现，那么就使用指定的对象进行注入
    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.
    // 注册BPP
    beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));

    // Detect a LoadTimeWeaver and prepare for weaving, if found.
    // 增加对AspectJ的支持，在java中织入分为三种方式，分为编译器织入，类加载器织入，运行期织入，编译器织入是指在java编译器，采用特殊的编译器，将切面织入到java类中，
    // 而类加载期织入则指通过特殊的类加载器，在类字节码加载到JVM时，织入切面，运行期织入则是采用cglib和jdk进行切面的织入
    // aspectj提供了两种织入方式，第一种是通过特殊编译器，在编译器，将aspectj语言编写的切面类织入到java类中，第二种是类加载期织入，就是下面的load time weaving，此处后续讲
    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到一级缓存中
    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());
    }
  }

五、postProcessBeanFactory

  该方法是一个空方法，交给子类自己处理的方法

六、invokeBeanFactoryPostProcessors

  invokeBeanFactoryPostProcessors是BeanFactory的后置处理方法。核心是会完成注册的BeanFactoryPostProcessor接口和BeanDefinitionRegistryPostProcessor的相关逻辑。invokeBeanFactoryPostProcessors是其核心的方法。

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

        // Invoke BeanDefinitionRegistryPostProcessors first, if any.
        // 无论是什么情况，优先执行BeanDefinitionRegistryPostProcessors
        // 将已经执行过的BFPP存储在processedBeans中，防止重复执行
        Set<String> processedBeans = new HashSet<>();

        // 判断beanfactory是否是BeanDefinitionRegistry类型，此处是DefaultListableBeanFactory,实现了BeanDefinitionRegistry接口，所以为true
        if (beanFactory instanceof BeanDefinitionRegistry) {
            // 类型转换
            BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
            // 此处希望大家做一个区分，两个接口是不同的，BeanDefinitionRegistryPostProcessor是BeanFactoryPostProcessor的子集
            // BeanFactoryPostProcessor主要针对的操作对象是BeanFactory，而BeanDefinitionRegistryPostProcessor主要针对的操作对象是BeanDefinition
            // 存放BeanFactoryPostProcessor的集合
            List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
            // 存放BeanDefinitionRegistryPostProcessor的集合
            List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();

            // 首先处理入参中的beanFactoryPostProcessors,遍历所有的beanFactoryPostProcessors，将BeanDefinitionRegistryPostProcessor
            // 和BeanFactoryPostProcessor区分开
            for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
                // 如果是BeanDefinitionRegistryPostProcessor
                if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
                    BeanDefinitionRegistryPostProcessor registryProcessor =
                            (BeanDefinitionRegistryPostProcessor) postProcessor;
                    // 直接执行BeanDefinitionRegistryPostProcessor接口中的postProcessBeanDefinitionRegistry方法
                    registryProcessor.postProcessBeanDefinitionRegistry(registry);
                    // 添加到registryProcessors，用于后续执行postProcessBeanFactory方法
                    registryProcessors.add(registryProcessor);
                } else {
                    // 否则，只是普通的BeanFactoryPostProcessor，添加到regularPostProcessors，用于后续执行postProcessBeanFactory方法
                    regularPostProcessors.add(postProcessor);
                }
            }

            // Do not initialize FactoryBeans here: We need to leave all regular beans
            // uninitialized to let the bean factory post-processors apply to them!
            // Separate between BeanDefinitionRegistryPostProcessors that implement
            // PriorityOrdered, Ordered, and the rest.
            // 用于保存本次要执行的BeanDefinitionRegistryPostProcessor
            List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();

            // First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
            // 调用所有实现PriorityOrdered接口的BeanDefinitionRegistryPostProcessor实现类
            // 找到所有实现BeanDefinitionRegistryPostProcessor接口bean的beanName
            String[] postProcessorNames =
                    beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
            // 遍历处理所有符合规则的postProcessorNames
            for (String ppName : postProcessorNames) {
                // 检测是否实现了PriorityOrdered接口
                if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
                    // 获取名字对应的bean实例，添加到currentRegistryProcessors中
                    currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                    // 将要被执行的BFPP名称添加到processedBeans，避免后续重复执行
                    processedBeans.add(ppName);
                }
            }
            // 按照优先级进行排序操作
            sortPostProcessors(currentRegistryProcessors, beanFactory);
            // 添加到registryProcessors中，用于最后执行postProcessBeanFactory方法
            registryProcessors.addAll(currentRegistryProcessors);
            // 遍历currentRegistryProcessors，执行postProcessBeanDefinitionRegistry方法
            invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
            // 执行完毕之后，清空currentRegistryProcessors
            currentRegistryProcessors.clear();

            // Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
            // 调用所有实现Ordered接口的BeanDefinitionRegistryPostProcessor实现类
            // 找到所有实现BeanDefinitionRegistryPostProcessor接口bean的beanName，
            // 此处需要重复查找的原因在于上面的执行过程中可能会新增其他的BeanDefinitionRegistryPostProcessor
            postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
            for (String ppName : postProcessorNames) {
                // 检测是否实现了Ordered接口，并且还未执行过
                if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
                    // 获取名字对应的bean实例，添加到currentRegistryProcessors中
                    currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                    // 将要被执行的BFPP名称添加到processedBeans，避免后续重复执行
                    processedBeans.add(ppName);
                }
            }
            // 按照优先级进行排序操作
            sortPostProcessors(currentRegistryProcessors, beanFactory);
            // 添加到registryProcessors中，用于最后执行postProcessBeanFactory方法
            registryProcessors.addAll(currentRegistryProcessors);
            // 遍历currentRegistryProcessors，执行postProcessBeanDefinitionRegistry方法
            invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
            // 执行完毕之后，清空currentRegistryProcessors
            currentRegistryProcessors.clear();

            // Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
            // 最后，调用所有剩下的BeanDefinitionRegistryPostProcessors
            boolean reiterate = true;
            while (reiterate) {
                reiterate = false;
                // 找出所有实现BeanDefinitionRegistryPostProcessor接口的类
                postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
                // 遍历执行
                for (String ppName : postProcessorNames) {
                    // 跳过已经执行过的BeanDefinitionRegistryPostProcessor
                    if (!processedBeans.contains(ppName)) {
                        // 获取名字对应的bean实例，添加到currentRegistryProcessors中
                        currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                        // 将要被执行的BFPP名称添加到processedBeans，避免后续重复执行
                        processedBeans.add(ppName);
                        reiterate = true;
                    }
                }
                // 按照优先级进行排序操作
                sortPostProcessors(currentRegistryProcessors, beanFactory);
                // 添加到registryProcessors中，用于最后执行postProcessBeanFactory方法
                registryProcessors.addAll(currentRegistryProcessors);
                // 遍历currentRegistryProcessors，执行postProcessBeanDefinitionRegistry方法
                invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
                // 执行完毕之后，清空currentRegistryProcessors
                currentRegistryProcessors.clear();
            }

            // Now, invoke the postProcessBeanFactory callback of all processors handled so far.
            // 调用所有BeanDefinitionRegistryPostProcessor的postProcessBeanFactory方法
            invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
            // 最后，调用入参beanFactoryPostProcessors中的普通BeanFactoryPostProcessor的postProcessBeanFactory方法
            invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
        } else {
            // Invoke factory processors registered with the context instance.
            // 如果beanFactory不归属于BeanDefinitionRegistry类型，那么直接执行postProcessBeanFactory方法
            invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
        }

        // 到这里为止，入参beanFactoryPostProcessors和容器中的所有BeanDefinitionRegistryPostProcessor已经全部处理完毕，下面开始处理容器中
        // 所有的BeanFactoryPostProcessor
        // 可能会包含一些实现类，只实现了BeanFactoryPostProcessor，并没有实现BeanDefinitionRegistryPostProcessor接口

        // Do not initialize FactoryBeans here: We need to leave all regular beans
        // uninitialized to let the bean factory post-processors apply to them!
        // 找到所有实现BeanFactoryPostProcessor接口的类
        String[] postProcessorNames =
                beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

        // Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
        // Ordered, and the rest.
        // 用于存放实现了PriorityOrdered接口的BeanFactoryPostProcessor
        List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
        // 用于存放实现了Ordered接口的BeanFactoryPostProcessor的beanName
//      List<String> orderedPostProcessorNames = new ArrayList<>();
        List<BeanFactoryPostProcessor> orderedPostProcessor = new ArrayList<>();
        // 用于存放普通BeanFactoryPostProcessor的beanName
//      List<String> nonOrderedPostProcessorNames = new ArrayList<>();
        List<BeanFactoryPostProcessor> nonOrderedPostProcessorNames = new ArrayList<>();
        // 遍历postProcessorNames,将BeanFactoryPostProcessor按实现PriorityOrdered、实现Ordered接口、普通三种区分开
        for (String ppName : postProcessorNames) {
            // 跳过已经执行过的BeanFactoryPostProcessor
            if (processedBeans.contains(ppName)) {
                // skip - already processed in first phase above
            }
            // 添加实现了PriorityOrdered接口的BeanFactoryPostProcessor到priorityOrderedPostProcessors
            else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
                priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
            }
            // 添加实现了Ordered接口的BeanFactoryPostProcessor的beanName到orderedPostProcessorNames
            else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
//              orderedPostProcessorNames.add(ppName);
                orderedPostProcessor.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
            } else {
                // 添加剩下的普通BeanFactoryPostProcessor的beanName到nonOrderedPostProcessorNames
//              nonOrderedPostProcessorNames.add(ppName);
                nonOrderedPostProcessorNames.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
            }
        }

        // First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
        // 对实现了PriorityOrdered接口的BeanFactoryPostProcessor进行排序
        sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
        // 遍历实现了PriorityOrdered接口的BeanFactoryPostProcessor，执行postProcessBeanFactory方法
        invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

        // Next, invoke the BeanFactoryPostProcessors that implement Ordered.
        // 创建存放实现了Ordered接口的BeanFactoryPostProcessor集合
//      List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
        // 遍历存放实现了Ordered接口的BeanFactoryPostProcessor名字的集合
//      for (String postProcessorName : orderedPostProcessorNames) {
        // 将实现了Ordered接口的BeanFactoryPostProcessor添加到集合中
//          orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
//      }
        // 对实现了Ordered接口的BeanFactoryPostProcessor进行排序操作
//      sortPostProcessors(orderedPostProcessors, beanFactory);
        sortPostProcessors(orderedPostProcessor, beanFactory);
        // 遍历实现了Ordered接口的BeanFactoryPostProcessor，执行postProcessBeanFactory方法
//      invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);
        invokeBeanFactoryPostProcessors(orderedPostProcessor, beanFactory);

        // Finally, invoke all other BeanFactoryPostProcessors.
        // 最后，创建存放普通的BeanFactoryPostProcessor的集合
//      List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
        // 遍历存放实现了普通BeanFactoryPostProcessor名字的集合
//      for (String postProcessorName : nonOrderedPostProcessorNames) {
        // 将普通的BeanFactoryPostProcessor添加到集合中
//          nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
//      }
        // 遍历普通的BeanFactoryPostProcessor，执行postProcessBeanFactory方法
//      invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);
        invokeBeanFactoryPostProcessors(nonOrderedPostProcessorNames, beanFactory);

        // Clear cached merged bean definitions since the post-processors might have
        // modified the original metadata, e.g. replacing placeholders in values...
        // 清除元数据缓存（mergeBeanDefinitions、allBeanNamesByType、singletonBeanNameByType）
        // 因为后置处理器可能已经修改了原始元数据，例如，替换值中的占位符
        beanFactory.clearMetadataCache();
    }

要搞清楚上面的代码含义首先需要搞清楚出这两者之间的关系

实现的核心流程是

在这个位置核心的代表是 ​​ConfigurationClassPostProcessor​​​用来处理 ​​@Configuration​​注解表示的Java类，来处理其中的@Bean,@Primary等注解。

七、registerBeanPostProcessors

  完成Bean对象的相关后置处理器的注册。具体的代码逻辑和上面是差不多的。

/**
     * 注册beanPostProcessor
     * @param beanFactory
     * @param applicationContext
     */
    public static void registerBeanPostProcessors(
            ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {

        // 找到所有实现了BeanPostProcessor接口的类
        String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);

        // Register BeanPostProcessorChecker that logs an info message when
        // a bean is created during BeanPostProcessor instantiation, i.e. when
        // a bean is not eligible for getting processed by all BeanPostProcessors.
        // 记录下BeanPostProcessor的目标计数
        // 此处为什么要+1呢，原因非常简单，在此方法的最后会添加一个BeanPostProcessorChecker的类
        int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
        // 添加BeanPostProcessorChecker(主要用于记录信息)到beanFactory中
        beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

        // Separate between BeanPostProcessors that implement PriorityOrdered,
        // Ordered, and the rest.
        // 定义存放实现了PriorityOrdered接口的BeanPostProcessor集合
        List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
        // 定义存放spring内部的BeanPostProcessor
        List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
        // 定义存放实现了Ordered接口的BeanPostProcessor的name集合
        List<String> orderedPostProcessorNames = new ArrayList<>();
        // 定义存放普通的BeanPostProcessor的name集合
        List<String> nonOrderedPostProcessorNames = new ArrayList<>();
        // 遍历beanFactory中存在的BeanPostProcessor的集合postProcessorNames，
        for (String ppName : postProcessorNames) {
            // 如果ppName对应的BeanPostProcessor实例实现了PriorityOrdered接口，则获取到ppName对应的BeanPostProcessor的实例添加到priorityOrderedPostProcessors中
            if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
                BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
                priorityOrderedPostProcessors.add(pp);
                // 如果ppName对应的BeanPostProcessor实例也实现了MergedBeanDefinitionPostProcessor接口，那么则将ppName对应的bean实例添加到internalPostProcessors中
                if (pp instanceof MergedBeanDefinitionPostProcessor) {
                    internalPostProcessors.add(pp);
                }
            }
            // 如果ppName对应的BeanPostProcessor实例没有实现PriorityOrdered接口，但是实现了Ordered接口，那么将ppName对应的bean实例添加到orderedPostProcessorNames中
            else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
                orderedPostProcessorNames.add(ppName);
            } else {
                // 否则将ppName添加到nonOrderedPostProcessorNames中
                nonOrderedPostProcessorNames.add(ppName);
            }
        }

        // First, register the BeanPostProcessors that implement PriorityOrdered.
        // 首先，对实现了PriorityOrdered接口的BeanPostProcessor实例进行排序操作
        sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
        // 注册实现了PriorityOrdered接口的BeanPostProcessor实例添加到beanFactory中
        registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

        // Next, register the BeanPostProcessors that implement Ordered.
        // 注册所有实现Ordered的beanPostProcessor
        List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
        for (String ppName : orderedPostProcessorNames) {
            // 根据ppName找到对应的BeanPostProcessor实例对象
            BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
            // 将实现了Ordered接口的BeanPostProcessor添加到orderedPostProcessors集合中
            orderedPostProcessors.add(pp);
            // 如果ppName对应的BeanPostProcessor实例也实现了MergedBeanDefinitionPostProcessor接口，那么则将ppName对应的bean实例添加到internalPostProcessors中
            if (pp instanceof MergedBeanDefinitionPostProcessor) {
                internalPostProcessors.add(pp);
            }
        }
        // 对实现了Ordered接口的BeanPostProcessor进行排序操作
        sortPostProcessors(orderedPostProcessors, beanFactory);
        //  注册实现了Ordered接口的BeanPostProcessor实例添加到beanFactory中
        registerBeanPostProcessors(beanFactory, orderedPostProcessors);

        // Now, register all regular BeanPostProcessors.
        // 创建存放没有实现PriorityOrdered和Ordered接口的BeanPostProcessor的集合
        List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
        // 遍历集合
        for (String ppName : nonOrderedPostProcessorNames) {
            // 根据ppName找到对应的BeanPostProcessor实例对象
            BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
            // 将没有实现PriorityOrdered和Ordered接口的BeanPostProcessor添加到nonOrderedPostProcessors集合中
            nonOrderedPostProcessors.add(pp);
            // 如果ppName对应的BeanPostProcessor实例也实现了MergedBeanDefinitionPostProcessor接口，那么则将ppName对应的bean实例添加到internalPostProcessors中
            if (pp instanceof MergedBeanDefinitionPostProcessor) {
                internalPostProcessors.add(pp);
            }
        }
        //  注册没有实现PriorityOrdered和Ordered的BeanPostProcessor实例添加到beanFactory中
        registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);

        // Finally, re-register all internal BeanPostProcessors.
        // 将所有实现了MergedBeanDefinitionPostProcessor类型的BeanPostProcessor进行排序操作
        sortPostProcessors(internalPostProcessors, beanFactory);
        // 注册所有实现了MergedBeanDefinitionPostProcessor类型的BeanPostProcessor到beanFactory中
        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ApplicationListenerDetector到beanFactory中
        beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
    }

八、initMessageSource

  为上下文初始化message源，即不同语言的消息体，国际化处理.此处不过多介绍、

九、initApplicationEventMulticaster

  initApplicationEventMulticaster初始化事件监听多路广播器.

protected void initApplicationEventMulticaster() {
    // 获取当前bean工厂,一般是DefaultListableBeanFactory
    ConfigurableListableBeanFactory beanFactory = getBeanFactory();
    // 判断容器中是否存在bdName为applicationEventMulticaster的bd，也就是说自定义的事件监听多路广播器，必须实现ApplicationEventMulticaster接口
    if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {
      // 如果有，则从bean工厂得到这个bean对象
      this.applicationEventMulticaster =
          beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);
      if (logger.isTraceEnabled()) {
        logger.trace("Using ApplicationEventMulticaster [" + this.applicationEventMulticaster + "]");
      }
    }
    else {
      // 如果没有，则默认采用SimpleApplicationEventMulticaster
      this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory);
      beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, this.applicationEventMulticaster);
      if (logger.isTraceEnabled()) {
        logger.trace("No '" + APPLICATION_EVENT_MULTICASTER_BEAN_NAME + "' bean, using " +
            "[" + this.applicationEventMulticaster.getClass().getSimpleName() + "]");
      }
    }
  }

代码很简单，创建了一个SimpleApplicationEventMulticaster对象，来广播相关的消息事件。

十、onRefresh

  留给子类来初始化其他的bean

十一、registerListeners

  所有注册的bean中查找listener bean,注册到消息广播器中.

protected void registerListeners() {
    // Register statically specified listeners first.
    // 遍历应用程序中存在的监听器集合，并将对应的监听器添加到监听器的多路广播器中
    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!
    // 从容器中获取所有实现了ApplicationListener接口的bd的bdName
    // 放入ApplicationListenerBeans集合中
    String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);
    for (String listenerBeanName : listenerBeanNames) {
      getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);
//      getApplicationEventMulticaster().addApplicationListener(this.getBean(listenerBeanName,ApplicationListener.class));
    }

    // Publish early application events now that we finally have a multicaster...
    // 此处先发布早期的监听器集合
    Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;
    this.earlyApplicationEvents = null;
    if (!CollectionUtils.isEmpty(earlyEventsToProcess)) {
      for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
        getApplicationEventMulticaster().multicastEvent(earlyEvent);
      }
    }
  }

十二、finishBeanFactoryInitialization

  finishBeanFactoryInitialization初始化剩下的单实例（非懒加载的）.这个专门单独讲解

十三、finishRefresh

  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.

protected void finishRefresh() {
    // Clear context-level resource caches (such as ASM metadata from scanning).
    // 清除上下文级别的资源缓存(如扫描的ASM元数据)
    // 清空在资源加载器中的所有资源缓存
    clearResourceCaches();

    // Initialize lifecycle processor for this context.
    // 为这个上下文初始化生命周期处理器
    // 初始化LifecycleProcessor.如果上下文中找到'lifecycleProcessor'的LifecycleProcessor Bean对象，
    // 则使用DefaultLifecycleProcessor
    initLifecycleProcessor();

    // Propagate refresh to lifecycle processor first.
    // 首先将刷新传播到生命周期处理器
    // 上下文刷新的通知，例如自动启动的组件
    getLifecycleProcessor().onRefresh();

    // Publish the final event.
    // 发布最终事件
    // 新建ContextRefreshedEvent事件对象，将其发布到所有监听器。
    publishEvent(new ContextRefreshedEvent(this));

    // Participate in LiveBeansView MBean, if active.
    // 参与LiveBeansView MBean，如果是活动的
    // LiveBeansView:Sping用于支持JMX 服务的类
    // 注册当前上下文到LiveBeansView，以支持JMX服务
    LiveBeansView.registerApplicationContext(this);
  }