源码分析

ApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring-config.xml");

查看源码

public ClassPathXmlApplicationContext(String configLocation) throws BeansException {
    this(new String[] {configLocation}, true, null);
}

public ClassPathXmlApplicationContext(
    String[] configLocations, boolean refresh, @Nullable ApplicationContext parent)
    throws BeansException {

    super(parent);
    //解析并设置给定的资源路径数组
    setConfigLocations(configLocations);
    if (refresh) {
        refresh();
    }
}

上面的就是ClassPathXmlApplicationContext加载的源码总览，下面逐步分析

一、解析并设置给定的资源路径数组

对应方法为setConfigLocations

public void setConfigLocations(@Nullable String... locations) {
    if (locations != null) {
        Assert.noNullElements(locations, "Config locations must not be null");
        this.configLocations = new String[locations.length];
        for (int i = 0; i < locations.length; i++) {
            //这里是解析每个给定的路径，例如包含特殊符号的解析（${var}）
            this.configLocations[i] = resolvePath(locations[i]).trim();
        }
    }
    else {
        this.configLocations = null;
    }
}

该方法就是解析配置路径，如果包含系统变量，则会调用resolvePath方法进行解析

二、refresh方法（核心逻辑）

public void refresh() throws BeansException, IllegalStateException {
    synchronized (this.startupShutdownMonitor) {
        // Prepare this context for refreshing.
        //1、准备刷新上下文环境
        //获取容器的当前时间，同时给容器设置同步标识
        prepareRefresh();

        // Tell the subclass to refresh the internal bean factory.
        //2、初始化BeanFactory，并进行XML文件的读取
        ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

        // Prepare the bean factory for use in this context.
        //3、对BeanFactory进行各种功能的填充
        //进入该方法前，Spring已经完成了对配置的解析，而ApplicationContext在功能上的扩展也由此展开
        prepareBeanFactory(beanFactory);

        try {
            // Allows post-processing of the bean factory in context subclasses.
            //4、子类覆盖方法做额外的处理
            postProcessBeanFactory(beanFactory);

            // Invoke factory processors registered as beans in the context.
            //5、激活各种BeanFactory处理器
            //BeanFactoryPostProcessor接口可以在实例化任何bean之前获取配置信息，从而可以正确解析bean描述文件中的变量引用
            invokeBeanFactoryPostProcessors(beanFactory);

            // Register bean processors that intercept bean creation.
            //6、注册拦截Bean创建的Bean处理器（这里只是注册，真正的调用在bean实例化的时候）
            registerBeanPostProcessors(beanFactory);

            // Initialize message source for this context.
            //7、为上下文初始化Message源（即不同语言的消息体，国际化处理）
            initMessageSource();

            // Initialize event multicaster for this context.
            //8、初始化应用消息广播器
            initApplicationEventMulticaster();

            // Initialize other special beans in specific context subclasses.
            //9、留给子类来初始化其它的Bean
            onRefresh();

            // Check for listener beans and register them.
            //10、在所有注册的bean中查找Listener bean，并注册到消息广播器中
            registerListeners();

            // Instantiate all remaining (non-lazy-init) singletons.
            //11、初始化剩下的单实例（非懒加载的）
            finishBeanFactoryInitialization(beanFactory);

            // Last step: publish corresponding event.
            //12、完成刷新过程，通知生命周期处理器lifecycleProcessor刷新过程，
            //同时发出ContextRefreshEvent通知别人
            finishRefresh();
        }

        //13、异常之后的处理
        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.
            //销毁已创建的单例
            destroyBeans();

            // Reset 'active' flag.
            //重置active标志
            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...
            //14、清除内置缓存
            resetCommonCaches();
        }
    }
}

refresh方法是ClassPathXmlApplicationContext加载的核心方法，内部逻辑大约分为以下14步

1、准备刷新上下文环境

protected void prepareRefresh() {
    // Switch to active.
    //记录启动开始时间
    this.startupDate = System.currentTimeMillis();
    //设置Context的当前状态
    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.
    //初始化上下文环境中的占位符属性来源
    //这个方法是空实现，用户可以根据自身的需要重写该方法，并且在方法中进行个性化的属性处理及设置
    initPropertySources();

    // Validate that all properties marked as required are resolvable:
    // see ConfigurablePropertyResolver#setRequiredProperties
    //对属性进行必要的验证，验证需要的属性文件是否都已经放入环境中
    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<>();
}

该方法主要做一些准备工作

• 记录启动开始时间
• 设置上下文的状态
• 方法initPropertySources，用户可以自定义属性的处理和设置
• 对属性进行必要性的校验
• 初始化监听器及事件集合

2、初始化BeanFactory，并进行配置文件的读取

protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
    //初始化BeanFactory，并进行XML文件读取，
    //并将得到的BeanFactory记录在当前实体的属性中
    refreshBeanFactory();
    //返回当前实体的BeanFactory属性
    return getBeanFactory();
}

这里主要是创建ConfigurableListableBeanFactory类型的BeanFactory并返回，核心逻辑在方法refreshBeanFactory中，代码如下

protected final void refreshBeanFactory() throws BeansException {
    //如果容器已经存在一个BeanFactory，则对其进行销毁和关闭
    if (hasBeanFactory()) {
        //銷毀单例bean
        destroyBeans();
        //关闭BeanFactory
        closeBeanFactory();
    }
    try {
        //创建DefaultListableBeanFactory类型的beanFactory
        DefaultListableBeanFactory beanFactory = createBeanFactory();
        //设置序列化Id（目的是为了需要根据Id反序列化出BeanFactory对象）
        beanFactory.setSerializationId(getId());
        //定制beanFactory，设置相关属性
        //包括：
        //（1）是否允许覆盖同名称的不同定义的对象
        //（2）循环依赖
        //（3）设置@Autowared和@Qualifier注解解析器QualifierAnnotationAutowireCandidateResolver
        //子类可以覆盖该方法来进行自定义的设置
        customizeBeanFactory(beanFactory);
        //加载BeanDefinition
        loadBeanDefinitions(beanFactory);
        //使用全局变量记录beanFactory类实例
        synchronized (this.beanFactoryMonitor) {
            this.beanFactory = beanFactory;
        }
    }
    catch (IOException ex) {
        throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
    }
}

主要做了以下两件事

• 对已有的BeanFactory进行销毁和关闭
  • 销毁单例bean
  • 关闭当前BeanFactory
• 创建并初始化新的BeanFactory（DefaultListableBeanFactory类型）

  • 实例化DefaultListableBeanFactory类型的BeanFactory

  • 设置序列化Id

  • 定制定制beanFactory，设置相关属性，包括如下：（customizeBeanFactory方法）

    • （1）是否允许覆盖同名称的不同定义的对象
    • （2）循环依赖
    • （3）设置@Autowared和@Qualifier注解解析器

    protected void customizeBeanFactory(DefaultListableBeanFactory beanFactory) {
        //如果allowBeanDefinitionOverriding不为空，则设置给beanFactory
        //属性含义：是否允许覆盖同名称的不同定义的对象
        if (this.allowBeanDefinitionOverriding != null) {
            beanFactory.setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);
        }
        //如果allowCircularReferences不为空，则设置给beanFactory
        //属性含义：是否允许bean之间存在循环依赖
        if (this.allowCircularReferences != null) {
            beanFactory.setAllowCircularReferences(this.allowCircularReferences);
        }
    }
    

    子类可以覆盖该方法来进行自定义的设置

  • 加载BeanDefinition

    根据不同的子类解析配置文件或注解

  • 使用全局变量记录beanFactory类实例

3、对BeanFactory进行各种功能的填充

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（Spring 3增加的表达式语言的支持）
    //默认可以使用#{bean.xxx}的形式来调用相关的属性值
    beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
    //创建默认的propertyEditorRegistrar，主要是对bean的属性等设置管理的一个工具（属性编辑器）
    beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));

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

    //设置几个忽略自动装配的接口
    //这些接口会在执行ApplicationContextAwareProcessor时自动装配执行
    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接口
    //一般检测到指定类型的属性，就会自动装配上去
    beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
    beanFactory.registerResolvableDependency(ResourceLoader.class, this);
    beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
    beanFactory.registerResolvableDependency(ApplicationContext.class, this);

    // Register early post-processor for detecting inner beans as ApplicationListeners.
    beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));

    // Detect a LoadTimeWeaver and prepare for weaving, if found.
    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.
    //增加对AspectJ的支持
    if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) {
        beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
    }
    //添加默认的系统环境bean
    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());
    }
}

• 设置beanFactory的classLoader为当前context的classLoader

• 设置beanFactory的表达式语言处理器，例如可以使用#{bean.xxx}来调用相关属性

• 创建默认的propertyEditorRegistrar，主要是对bean的属性等设置管理的一个工具（属性编辑器）

  这里创建的属性编辑器为默认的ResourceEditorRegistrar类型，在该类中存在这样的代码

  public void registerCustomEditors(PropertyEditorRegistry registry) {
      ResourceEditor baseEditor = new ResourceEditor(this.resourceLoader, this.propertyResolver);
      doRegisterEditor(registry, Resource.class, baseEditor);
      doRegisterEditor(registry, ContextResource.class, baseEditor);
      doRegisterEditor(registry, InputStream.class, new InputStreamEditor(baseEditor));
      doRegisterEditor(registry, InputSource.class, new InputSourceEditor(baseEditor));
      doRegisterEditor(registry, File.class, new FileEditor(baseEditor));
      doRegisterEditor(registry, Path.class, new PathEditor(baseEditor));
      doRegisterEditor(registry, Reader.class, new ReaderEditor(baseEditor));
      doRegisterEditor(registry, URL.class, new URLEditor(baseEditor));
  
      ClassLoader classLoader = this.resourceLoader.getClassLoader();
      doRegisterEditor(registry, URI.class, new URIEditor(classLoader));
      doRegisterEditor(registry, Class.class, new ClassEditor(classLoader));
      doRegisterEditor(registry, Class[].class, new ClassArrayEditor(classLoader));
  
      if (this.resourceLoader instanceof ResourcePatternResolver) {
          doRegisterEditor(registry, Resource[].class,
                           new ResourceArrayPropertyEditor((ResourcePatternResolver) this.resourceLoader, this.propertyResolver));
      }
  }
  

  可以看到Spring为我们定义了一些基本属性的编辑器。

• 添加ApplicationContextAwareProcessor类型的后置处理器，它的作用是invoke各种Aware，组装对应的属性，代码如下（ApplicationContextAwareProcessor#invokeAwareInterfaces）

  private void invokeAwareInterfaces(Object bean) {
      //invoke各种Aware，组装对应的属性
      if (bean instanceof EnvironmentAware) {
          ((EnvironmentAware) bean).setEnvironment(this.applicationContext.getEnvironment());
      }
      if (bean instanceof EmbeddedValueResolverAware) {
          ((EmbeddedValueResolverAware) bean).setEmbeddedValueResolver(this.embeddedValueResolver);
      }
      if (bean instanceof ResourceLoaderAware) {
          ((ResourceLoaderAware) bean).setResourceLoader(this.applicationContext);
      }
      if (bean instanceof ApplicationEventPublisherAware) {
          ((ApplicationEventPublisherAware) bean).setApplicationEventPublisher(this.applicationContext);
      }
      if (bean instanceof MessageSourceAware) {
          ((MessageSourceAware) bean).setMessageSource(this.applicationContext);
      }
      if (bean instanceof ApplicationContextAware) {
          ((ApplicationContextAware) bean).setApplicationContext(this.applicationContext);
      }
  }
  

• 设置几个忽略自动装配的接口，这些接口会在执行ApplicationContextAwareProcessor时自动装配执行

  //设置几个忽略自动装配的接口
  //这些接口会在执行ApplicationContextAwareProcessor时自动装配执行
  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接口，一般检测到指定类型的属性，就会自动装配上去

  //设置几个自动装配的接口
  //一般检测到指定类型的属性，就会自动装配上去
  beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
  beanFactory.registerResolvableDependency(ResourceLoader.class, this);
  beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
  beanFactory.registerResolvableDependency(ApplicationContext.class, this);
  

• 增加对AspectJ的支持

• 添加默认的系统环境bean

4、子类覆盖方法做额外的处理

默认空实现，子类可以扩展做一些自定义的处理

5、激活各种BeanFactory处理器

BeanFactoryPostProcessor接口可以在实例化任何bean之前获取配置信息，从而可以正确解析bean描述文件中的变量引用

protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
    PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());

    // Detect a LoadTimeWeaver and prepare for weaving, if found in the meantime
    // (e.g. through an @Bean method registered by ConfigurationClassPostProcessor)
    if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
        beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
        beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
    }
}

核心逻辑在第一行代码

//PostProcessorRegistrationDelegate#invokeBeanFactoryPostProcessors方法
public static void invokeBeanFactoryPostProcessors(
    ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {

    // Invoke BeanDefinitionRegistryPostProcessors first, if any.
    //记录已经触发的BeanDefinitionRegistryPostProcessors
    Set<String> processedBeans = new HashSet<>();

    //对于BeanFactoryPostProcessor的处理分为两种情况
    //（1）对于BeanDefinitionRegistry类型的特殊处理
    //（2）对于普通的BeanFactoryPostProcessor处理


    //对BeanDefinitionRegistry类型的处理
    if (beanFactory instanceof BeanDefinitionRegistry) {
        BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
        //记录BeanFactoryPostProcessor类型的处理器
        List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
        //记录BeanDefinitionRegistryPostProcessor类型的处理器
        List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();

        for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
            //对于BeanDefinitionRegistryPostProcessor类型，需要先调用postProcessBeanDefinitionRegistry方法
            if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
                BeanDefinitionRegistryPostProcessor registryProcessor =
                    (BeanDefinitionRegistryPostProcessor) postProcessor;
                registryProcessor.postProcessBeanDefinitionRegistry(registry);
                registryProcessors.add(registryProcessor);
            }
            //常规的BeanFactoryPostProcessor
            else {
                regularPostProcessors.add(postProcessor);
            }
        }

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

        // First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
        // 获取配置文件中配置的且实现PriorityOrdered接口的BeanDefinitionRegistryPostProcessor
        // 填充到currentRegistryProcessors
        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);
        //添加到registryProcessors中
        registryProcessors.addAll(currentRegistryProcessors);
        //invoke所有实现PriorityOrdered接口的BeanDefinitionRegistryPostProcessor
        invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
        currentRegistryProcessors.clear();

        // Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
        // 获取配置文件中配置的且实现Ordered接口的BeanDefinitionRegistryPostProcessor
        // 填充到currentRegistryProcessors
        postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
        for (String ppName : postProcessorNames) {
            if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
                currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                processedBeans.add(ppName);
            }
        }
        //排序
        sortPostProcessors(currentRegistryProcessors, beanFactory);
        //添加到registryProcessors中
        registryProcessors.addAll(currentRegistryProcessors);
        //invoke所有实现Ordered接口的BeanDefinitionRegistryPostProcessor
        invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
        currentRegistryProcessors.clear();

        // Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
        //获取配置文件中配置的剩余的BeanDefinitionRegistryPostProcessor（即未实现任何排序接口）
        boolean reiterate = true;
        while (reiterate) {
            reiterate = false;
            postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
            for (String ppName : postProcessorNames) {
                if (!processedBeans.contains(ppName)) {
                    currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                    processedBeans.add(ppName);
                    reiterate = true;
                }
            }
            //排序
            sortPostProcessors(currentRegistryProcessors, beanFactory);
            //添加到registryProcessors中
            registryProcessors.addAll(currentRegistryProcessors);
            //invoke剩余的BeanDefinitionRegistryPostProcessor（即未实现任何排序接口）
            invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
            currentRegistryProcessors.clear();
        }

        // Now, invoke the postProcessBeanFactory callback of all processors handled so far.
        //上面的代码只是触发BeanDefinitionRegistryPostProcessor类型中的postProcessBeanDefinitionRegistry方法，
        //现在需要正式调用postProcessBeanFactory方法
        invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
        invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
    }
    //普通的beanFactory处理
    else {
        // Invoke factory processors registered with the context instance.
        //对应非BeanDefinitionRegistry类型的beanFactory，直接调用postProcessBeanFactory方法
        invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
    }

    // Do not initialize FactoryBeans here: We need to leave all regular beans
    // uninitialized to let the bean factory post-processors apply to them!
    //获取配置文件里面的所有BeanFactoryPostProcessor类型的实例
    String[] postProcessorNames =
        beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

    // Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
    // Ordered, and the rest.
    //存放实现PriorityOrdered接口的BeanFactoryPostProcessor
    List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
    //存放实现Ordered接口的BeanFactoryPostProcessor
    List<String> orderedPostProcessorNames = new ArrayList<>();
    //存放剩余的BeanFactoryPostProcessor
    List<String> nonOrderedPostProcessorNames = new ArrayList<>();
    for (String ppName : postProcessorNames) {
        //已经执行过了的BeanFactoryPostProcessor执行跳过
        if (processedBeans.contains(ppName)) {
            // skip - already processed in first phase above
        }
        //实现了PriorityOrdered接口添加到priorityOrderedPostProcessors
        else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
            priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
        }
        //实现了Ordered接口添加到priorityOrderedPostProcessors
        else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
            orderedPostProcessorNames.add(ppName);
        }
        //剩余的（未实现任何排序接口）添加到priorityOrderedPostProcessors
        else {
            nonOrderedPostProcessorNames.add(ppName);
        }
    }

    // First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
    //首选对实现PriorityOrdered接口的PostProcessor排序
    sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
    //触发
    invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

    // Next, invoke the BeanFactoryPostProcessors that implement Ordered.
    //其次对实现Ordered接口的PostProcessor排序并触发
    List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
    for (String postProcessorName : orderedPostProcessorNames) {
        orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
    }
    sortPostProcessors(orderedPostProcessors, beanFactory);
    invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);

    // Finally, invoke all other BeanFactoryPostProcessors.
    //最后对剩余的BeanFactoryPostProcessor进行触发
    List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
    for (String postProcessorName : nonOrderedPostProcessorNames) {
        nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
    }
    invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);

    // Clear cached merged bean definitions since the post-processors might have
    // modified the original metadata, e.g. replacing placeholders in values...
    //清理缓存
    beanFactory.clearMetadataCache();
}

上述代码看起来很多，但是实际上逻辑很简单，对于BeanFactoryPostProcessor的处理分为两种情况

• 对于BeanDefinitionRegistry类型的特殊

  • 需要先对所有BeanDefinitionRegistryPostProcessor类型进行postProcessBeanDefinitionRegistry方法触发，再触发BeanFactoryPostProcessor的postProcessBeanFactory方法

• 非BeanDefinitionRegistry类型

  只需要触发BeanFactoryPostProcessor的postProcessBeanFactory方法

在触发BeanDefinitionRegistryPostProcessor和BeanFactoryPostProcessor时，优选触发实现PriorityOrdered类型，其次为Ordered，剩余的最后触发。其中PriorityOrdered和Ordered内部根据配置的数字进行排序触发

6、注册BeanPostProcessor

这里只是注册，真正的调用在bean实例化的时候

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

继续查看源码

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

    //获取所有的BeanPostProcessor的beanName
    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.
    int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
    beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

    // Separate between BeanPostProcessors that implement PriorityOrdered,
    // Ordered, and the rest.
    //存放实现priorityOrdered接口的BeanPostProcessor
    List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
    //存放MergedBeanDefinitionPostProcessor
    List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
    //存放实现Ordered接口的BeanPostProcessor
    List<String> orderedPostProcessorNames = new ArrayList<>();
    //存放无序的BeanPostProcessor
    List<String> nonOrderedPostProcessorNames = new ArrayList<>();
    for (String ppName : postProcessorNames) {
        //如果是实现了PriorityOrdered接口，则加入到priorityOrderedPostProcessors集合中
        if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
            BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
            priorityOrderedPostProcessors.add(pp);
            //如果是MergedBeanDefinitionPostProcessor类型，则继续放入internalPostProcessors集合中
            if (pp instanceof MergedBeanDefinitionPostProcessor) {
                internalPostProcessors.add(pp);
            }
        }
        //如果是实现了Ordered接口，则加入到orderedPostProcessorNames集合中
        else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
            orderedPostProcessorNames.add(ppName);
        }
        //无任何排序规则，则加入到nonOrderedPostProcessorNames集合中
        else {
            nonOrderedPostProcessorNames.add(ppName);
        }
    }

    // First, register the BeanPostProcessors that implement PriorityOrdered.
    //第一步：注册所有实现PriorityOrdered接口的BeanPostProcessor
    //先排序
    sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
    //后注册
    registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

    // Next, register the BeanPostProcessors that implement Ordered.
    //第二步：注册所有实现Ordered接口的BeanPostProcessor
    List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
    for (String ppName : orderedPostProcessorNames) {
        BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
        orderedPostProcessors.add(pp);
        //如果是MergedBeanDefinitionPostProcessor类型，则继续放入internalPostProcessors集合中
        if (pp instanceof MergedBeanDefinitionPostProcessor) {
            internalPostProcessors.add(pp);
        }
    }
    //排序
    sortPostProcessors(orderedPostProcessors, beanFactory);
    //注册
    registerBeanPostProcessors(beanFactory, orderedPostProcessors);

    // Now, register all regular BeanPostProcessors.
    //第三步：注册所有无序接口的BeanPostProcessor
    List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
    for (String ppName : nonOrderedPostProcessorNames) {
        BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
        nonOrderedPostProcessors.add(pp);
        //如果是MergedBeanDefinitionPostProcessor类型，则继续放入internalPostProcessors集合中
        if (pp instanceof MergedBeanDefinitionPostProcessor) {
            internalPostProcessors.add(pp);
        }
    }
    //注册
    registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);

    // Finally, re-register all internal BeanPostProcessors.
    //最后：注册所有MergedBeanDefinitionPostProcessor类型的BeanPostProcessor
    sortPostProcessors(internalPostProcessors, beanFactory);
    registerBeanPostProcessors(beanFactory, internalPostProcessors);

    // Re-register post-processor for detecting inner beans as ApplicationListeners,
    // moving it to the end of the processor chain (for picking up proxies etc).
    //添加ApplicationListener探测器
    beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}

逻辑与注册BeanFactoryPostProcessors很类型，不过这里仅仅是注册，并不触发。且注册的先后顺序为

PriorityOrdered–>Ordered–>无序–>MergedBeanDefinitionPostProcessor，如果既实现了排序接口，又实现了MergedBeanDefinitionPostProcessor接口，则会当做MergedBeanDefinitionPostProcessor来处理

7、为上下文初始化Message源（国际化处理）

即国际化处理

protected void initMessageSource() {
    ConfigurableListableBeanFactory beanFactory = getBeanFactory();
    if (beanFactory.containsLocalBean(MESSAGE_SOURCE_BEAN_NAME)) {
        this.messageSource = beanFactory.getBean(MESSAGE_SOURCE_BEAN_NAME, MessageSource.class);
        // Make MessageSource aware of parent MessageSource.
        if (this.parent != null && this.messageSource instanceof HierarchicalMessageSource) {
            HierarchicalMessageSource hms = (HierarchicalMessageSource) this.messageSource;
            if (hms.getParentMessageSource() == null) {
                // Only set parent context as parent MessageSource if no parent MessageSource
                // registered already.
                hms.setParentMessageSource(getInternalParentMessageSource());
            }
        }
        if (logger.isTraceEnabled()) {
            logger.trace("Using MessageSource [" + this.messageSource + "]");
        }
    }
    else {
        // Use empty MessageSource to be able to accept getMessage calls.
        DelegatingMessageSource dms = new DelegatingMessageSource();
        dms.setParentMessageSource(getInternalParentMessageSource());
        this.messageSource = dms;
        beanFactory.registerSingleton(MESSAGE_SOURCE_BEAN_NAME, this.messageSource);
        if (logger.isTraceEnabled()) {
            logger.trace("No '" + MESSAGE_SOURCE_BEAN_NAME + "' bean, using [" + this.messageSource + "]");
        }
    }
}

逻辑暂时略过…

8、初始化应用消息广播器

protected void initApplicationEventMulticaster() {
    ConfigurableListableBeanFactory beanFactory = getBeanFactory();
    //如果用户自定义了事件广播器，那么使用用户自定义的事件广播器
    if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {
        this.applicationEventMulticaster =
            beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);
        if (logger.isTraceEnabled()) {
            logger.trace("Using ApplicationEventMulticaster [" + this.applicationEventMulticaster + "]");
        }
    }
    //如果没有定义，则使用默认的SimpleApplicationEventMulticaster
    else {
        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() + "]");
        }
    }
}

9、留给子类来初始化其它的Bean

默认空实现，子类可以用来初始化其他bean

10、在所有注册的bean中查找Listener bean，并注册到消息广播器中

protected void registerListeners() {
    // Register statically specified listeners first.
    //硬编码方法注册的监听器
    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!
    //配置文件注册的监听器处理
    String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);
    for (String listenerBeanName : listenerBeanNames) {
        getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);
    }

    // Publish early application events now that we finally have a multicaster...
    //触发早期的时间监听器
    Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;
    this.earlyApplicationEvents = null;
    if (earlyEventsToProcess != null) {
        for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
            getApplicationEventMulticaster().multicastEvent(earlyEvent);
        }
    }
}

主要将硬编码和配置文件里面的监听器注册到容器中

11、初始化剩下的单实例（非懒加载的）

相比于XmlBeanFactory，ApplicationContext在启动时就将所有注册的bean加载到容器中

protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
    // Initialize conversion service for this context.
    //初始化一些转换器
    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));
    }

    // Register a default embedded value resolver if no bean post-processor
    // (such as a PropertyPlaceholderConfigurer bean) registered any before:
    // at this point, primarily for resolution in annotation attribute values.
    //如果没有任何bean post-processor，会默认注入属性解析器
    if (!beanFactory.hasEmbeddedValueResolver()) {
        beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
    }

    // Initialize LoadTimeWeaverAware beans early to allow for registering their transformers early.
    //初始化LoadTimeWeaverAware类型
    String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
    for (String weaverAwareName : weaverAwareNames) {
        getBean(weaverAwareName);
    }

    // Stop using the temporary ClassLoader for type matching.
    //停止使用临时ClassLoader进行类型匹配
    beanFactory.setTempClassLoader(null);

    // Allow for caching all bean definition metadata, not expecting further changes.
    //冻结所有的bean定义，即bean定义将不被修改或者进行任何一步的处理
    beanFactory.freezeConfiguration();

    // Instantiate all remaining (non-lazy-init) singletons.
    // 实例化所有剩余的（非延迟初始化）单例
    //ApplicationContext默认就是启动时将所有单例bean提前进行实例化
    beanFactory.preInstantiateSingletons();
}

这里最重要的是最后一步：实例化所有剩余的（非延迟初始化）单例

public void preInstantiateSingletons() throws BeansException {
    if (logger.isTraceEnabled()) {
        logger.trace("Pre-instantiating singletons in " + this);
    }

    // Iterate over a copy to allow for init methods which in turn register new bean definitions.
    // While this may not be part of the regular factory bootstrap, it does otherwise work fine.
    List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);

    // Trigger initialization of all non-lazy singleton beans...
    //触发所有非惰性单例bean的初始化
    for (String beanName : beanNames) {
        //获取bean配置信息
        RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
        //只加载单例非懒加载的非抽象类
        if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
            //对应FactoryBean类型的实例的加载
            if (isFactoryBean(beanName)) {
                Object bean = getBean(FACTORY_BEAN_PREFIX + beanName);
                if (bean instanceof FactoryBean) {
                    final FactoryBean<?> factory = (FactoryBean<?>) bean;
                    boolean isEagerInit;
                    if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
                        isEagerInit = AccessController.doPrivileged((PrivilegedAction<Boolean>)
                                                                    ((SmartFactoryBean<?>) factory)::isEagerInit,
                                                                    getAccessControlContext());
                    }
                    else {
                        isEagerInit = (factory instanceof SmartFactoryBean &&
                                       ((SmartFactoryBean<?>) factory).isEagerInit());
                    }
                    if (isEagerInit) {
                        getBean(beanName);
                    }
                }
            }
            //普通bean的加载
            else {
                getBean(beanName);
            }
        }
    }

    // Trigger post-initialization callback for all applicable beans...
    //触发所有bean的初始化后回调
    for (String beanName : beanNames) {
        Object singletonInstance = getSingleton(beanName);
        if (singletonInstance instanceof SmartInitializingSingleton) {
            final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
            if (System.getSecurityManager() != null) {
                AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
                    smartSingleton.afterSingletonsInstantiated();
                    return null;
                }, getAccessControlContext());
            }
            else {
                smartSingleton.afterSingletonsInstantiated();
            }
        }
    }
}

这里分为两大步骤

• 首先就是加载所有非惰性单例bean
• 其次是触发SmartInitializingSingleton类型bean的afterSingletonsInstantiated方法，即触发bean的初始化后回调

加载bean的逻辑就是getBean方法，这里不再赘述。

12、完成刷新过程的后续处理

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
    clearResourceCaches();

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

    // Propagate refresh to lifecycle processor first.
    //触发所有生命周期处理器的onRefresh方法
    getLifecycleProcessor().onRefresh();

    // Publish the final event.
    //发布上下文刷新事件
    publishEvent(new ContextRefreshedEvent(this));

    // Participate in LiveBeansView MBean, if active.
    LiveBeansView.registerApplicationContext(this);
}

主要做了以下几件事

• 清除上下文级别的资源缓存

• 为此上下文初始化生命周期处理器LifecycleProcessor

  protected void initLifecycleProcessor() {
      ConfigurableListableBeanFactory beanFactory = getBeanFactory();
      //如果本地存在lifecycleProcessor，则获取本地lifecycleProcessor
      if (beanFactory.containsLocalBean(LIFECYCLE_PROCESSOR_BEAN_NAME)) {
          this.lifecycleProcessor =
              beanFactory.getBean(LIFECYCLE_PROCESSOR_BEAN_NAME, LifecycleProcessor.class);
          if (logger.isTraceEnabled()) {
              logger.trace("Using LifecycleProcessor [" + this.lifecycleProcessor + "]");
          }
      }
      //否则使用默认的DefaultLifecycleProcessor
      else {
          DefaultLifecycleProcessor defaultProcessor = new DefaultLifecycleProcessor();
          defaultProcessor.setBeanFactory(beanFactory);
          this.lifecycleProcessor = defaultProcessor;
          beanFactory.registerSingleton(LIFECYCLE_PROCESSOR_BEAN_NAME, this.lifecycleProcessor);
          if (logger.isTraceEnabled()) {
              logger.trace("No '" + LIFECYCLE_PROCESSOR_BEAN_NAME + "' bean, using " +
                           "[" + this.lifecycleProcessor.getClass().getSimpleName() + "]");
          }
      }
  }
  

• 触发生命周期处理器LifecycleProcessor

  @Override
  public void onRefresh() {
      startBeans(true);
      this.running = true;
  }
  

  这里是调用方法startBeans

  private void startBeans(boolean autoStartupOnly) {
      //获取容器中所有的Lifecycle
      Map<String, Lifecycle> lifecycleBeans = getLifecycleBeans();
      Map<Integer, LifecycleGroup> phases = new HashMap<>();
      //根据phase将这些Lifecycle进行分组
      lifecycleBeans.forEach((beanName, bean) -> {
          if (!autoStartupOnly || (bean instanceof SmartLifecycle && ((SmartLifecycle) bean).isAutoStartup())) {
              int phase = getPhase(bean);
              LifecycleGroup group = phases.get(phase);
              if (group == null) {
                  group = new LifecycleGroup(phase, this.timeoutPerShutdownPhase, lifecycleBeans, autoStartupOnly);
                  phases.put(phase, group);
              }
              group.add(beanName, bean);
          }
      });
      if (!phases.isEmpty()) {
          List<Integer> keys = new ArrayList<>(phases.keySet());
          //排序
          Collections.sort(keys);
          //按照排序进行触发
          for (Integer key : keys) {
              phases.get(key).start();
          }
      }
  }
  

  按照分组顺序进行逐个触发

• 发布上下文刷新事件

13、上述过程出现异常后的处理

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

// Destroy already created singletons to avoid dangling resources.
//销毁已创建的单例
destroyBeans();

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

// Propagate exception to caller.
throw ex;

• 首先销毁所有的单例bean

  protected void destroyBeans() {
      getBeanFactory().destroySingletons();
  }
  

• 重置active标志

  protected void cancelRefresh(BeansException ex) {
      this.active.set(false);
  }
  

14、清除内置缓存

protected void resetCommonCaches() {
    //清除反射使用到的方法和字段缓存
    ReflectionUtils.clearCache();
    //清除注解缓存
    AnnotationUtils.clearCache();
    //清除ResolvableType缓存
    ResolvableType.clearCache();
    //清除ClassLoader缓存
    CachedIntrospectionResults.clearClassLoader(getClassLoader());
}