Spring初始化流程

开始

在SpringIOC中，前面讲述了如何配置BeanDefinition和如何注册BeanDefinition,但是这些知识容器初始化的一部分，在AbstractApplicationContext中的refresh()方法中，可以看到整个初始化过程。

今天就来看看这段曲折的初始化之路

编写一个简单的启动类，打个断点到AbstractApplicationContext中的refresh()方法中。

public class Application {
    public static void main(String[] args) {

        // setConfig -> call this.refresh()
        ClassPathXmlApplicationContext classPathXmlApplicationContext = new ClassPathXmlApplicationContext("context.xml");
    }
}

先看看refresh中调用了哪些方法：

public void refresh() throws BeansException, IllegalStateException {
        synchronized (this.startupShutdownMonitor) {
            // Prepare this context for refreshing.
            prepareRefresh();

            // Tell the subclass to refresh the internal bean factory.
            ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

            // Prepare the bean factory for use in this context.
            prepareBeanFactory(beanFactory);

            try {
                // Allows post-processing of the bean factory in context subclasses.
                postProcessBeanFactory(beanFactory);

                // Invoke factory processors registered as beans in the context.
                invokeBeanFactoryPostProcessors(beanFactory);

                // Register bean processors that intercept bean creation.
                registerBeanPostProcessors(beanFactory);

                // Initialize message source for this context.
                initMessageSource();

                // Initialize event multicaster for this context.
                initApplicationEventMulticaster();

                // Initialize other special beans in specific context subclasses.
                onRefresh();

                // Check for listener beans and register them.
                registerListeners();

                // Instantiate all remaining (non-lazy-init) singletons.
                finishBeanFactoryInitialization(beanFactory);

                // Last step: publish corresponding event.
                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();
            }
        }
    }

一张图概览

上面的图是整个初始化的大概流程。

然后把每一步拿出来说明一下吧

refresh()方法流程

文中使用了ClassPathXmlApplicationContext作为容器

1 prepareRefresh()

protected void prepareRefresh() {
        // 记录启动时间 然后设立对应的标志位
        this.startupDate = System.currentTimeMillis();
        this.closed.set(false);
        this.active.set(true);

        if (logger.isInfoEnabled()) {
            logger.info("Refreshing " + this);
        }

        // 这是扩展方法，由子类去实现
        initPropertySources();

        // 创建Environment，验证必要的属性
        getEnvironment().validateRequiredProperties();

        // 初始化容器，用于装载早期的一些事件
        this.earlyApplicationEvents = new LinkedHashSet<>();
    }

这里主要是做一些准备工作

2 obtainFreshBeanFactory()

protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
    // 这个方法是子类去实现的
    refreshBeanFactory();
    // 创建ApplicationContext内部持有的BeanFactory
    // getBeanFactory也是留给子类去实现，可以查看AbstractRefreshableApplicationContext和GernericApplicationContext
    ConfigurableListableBeanFactory beanFactory = getBeanFactory();
    if (logger.isDebugEnabled()) {
        logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
    }
    return beanFactory;
}

3 prepareBeanFactory(beanFactory)

protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
        // 设置beanFactory的classLoader为当前context的classLoader
        beanFactory.setBeanClassLoader(getClassLoader());
        // 设置EL表达式解析器（Bean初始化完成后填充属性时会用到）
        // spring3增加了表达式语言的支持，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()));
        // 设置属性注册解析器PropertyEditor 这个主要是对bean的属性等设置管理的一个工具
        beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));
        
        // 注册BeanPostProcessor-ApplicationContextAwareProcessor，从而在Aware接口实现类中的注入applicationContext等等
        // 添加了一个处理aware相关接口的beanPostProcessor扩展，主要是使用beanPostProcessor的postProcessBeforeInitialization()前置处理方法实现aware相关接口的功能
        // 类似的还有ResourceLoaderAware、ServletContextAware等等等等
        beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
    
        // 下面是忽略的自动装配
        // 自动装配模式下，下面这些接口的实现类，都不会自动装配，自动装配不是@Autowired
        // 注意区分ignoreDependencyType,这个是在自动装配时忽略某个类型属性的依赖
        beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
        beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
        beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
        beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
        beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
        beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);

        // 如果是BeanFactory的类，就注册beanFactory
        //  如果是ResourceLoader、ApplicationEventPublisher、ApplicationContext等等就注入当前对象this(applicationContext对象)
        
        // 此处registerResolvableDependency()方法注意：它会把他们加入到DefaultListableBeanFactory的resolvableDependencies字段里面缓存这，供后面处理依赖注入的时候使用 DefaultListableBeanFactory#resolveDependency处理依赖关系
        // 这也是为什么我们可以通过依赖注入的方式，直接注入这几个对象比如ApplicationContext可以直接依赖注入
        // 但是需要注意的是：这些Bean，Spring的IOC容器里其实是没有的。beanFactory.getBeanDefinitionNames()和beanFactory.getSingletonNames()都是找不到他们的，所以特别需要理解这一点
        
        beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
        beanFactory.registerResolvableDependency(ResourceLoader.class, this);
        beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
        beanFactory.registerResolvableDependency(ApplicationContext.class, this);

        // 在Bean初始化后检查是否实现了ApplicationListener接口
        // 是则加入当前的applicationContext的applicationListeners列表 
        beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));


        // 检查容器中是否包含名称为loadTimeWeaver的bean，实际上是增加Aspectj的支持
        // AspectJ采用编译期织入、类加载期织入两种方式进行切面的织入
        // 类加载期织入简称为LTW（Load Time Weaving）,通过特殊的类加载器来代理JVM默认的类加载器实现
        if (beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
            // 添加BEAN后置处理器：LoadTimeWeaverAwareProcessor
            // 在BEAN初始化之前检查BEAN是否实现了LoadTimeWeaverAware接口，
            // 如果是，则进行加载时织入，即静态代理。
            beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
            // Set a temporary ClassLoader for type matching.
            beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
        }

        // 注入一些其它信息的bean，比如environment、systemProperties、SystemEnvironment等
        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());
        }
    }

这里做的事情比较多，大多是和依赖的处理相关的配置。

4 postProcessBeanFactory(beanFactory)

这里是模板方法，留给子类去实现的逻辑，至此BeanFactory已经准备好

5 invokeBeanFactoryPostProcessors(beanFactory)

实例化并调用所有的 BeanFactoryPostProcessor ,当前必须是已经注册的

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

   // Detect a LoadTimeWeaver and prepare for weaving, if found in the meantime
   // (e.g. through an @Bean method registered by ConfigurationClassPostProcessor)
    // 如果loadTimeWeaver这个Bean存在，那么就会配置上运行时织入的处理器LoadTimeWeaverAwareProcessor
   if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
      beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
      beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
   }
}

这里有个 getBeanFactoryPostProcessors() 方法，这个方法是获取 AbstractApplicationContext 内部的一个List类型属性，保存了手动添加的 BeanPostProcessor 实例。

重点在 PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors 中

public static void invokeBeanFactoryPostProcessors(
            ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {    
    // 先执行BeanDefinitionRegistryPostProcessors 
    // 需要注意的是BeanDefinitionRegistryPostProcessors 为 BeanFactoryPostProcessor 的子接口 它新增了方法：void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry)
    
    // 所以BeanDefinitionRegistryPostProcessors，它可以我们介入，改变Bean的一些定义信息，或者动态注入Bean定义
    Set<String> processedBeans = new HashSet<>();

    // 只有此beanFactory 是BeanDefinitionRegistry  才能执行BeanDefinitionRegistryPostProcessor
    if (beanFactory instanceof BeanDefinitionRegistry) {
        BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;

        // 此处安放了两个容器，一个装载普通的BeanFactoryPostProcessor
        // 另外一个装载和Bean定义有关的 BeanDefinitionRegistryPostProcessor
        List<BeanFactoryPostProcessor> regularPostProcessors = new LinkedList<>();
        List<BeanDefinitionRegistryPostProcessor> registryProcessors = new LinkedList<>();

        // 这里是手动添加到ApplicationContext中的
        for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
            if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
                BeanDefinitionRegistryPostProcessor registryProcessor =
                        (BeanDefinitionRegistryPostProcessor) postProcessor;
                
                // 这里执行post方法，然后然后吧它缓冲起来了，放在了registryProcessors里
                registryProcessor.postProcessBeanDefinitionRegistry(registry);
                registryProcessors.add(registryProcessor);
            }
            else {
                // 缓冲到普通的处理器
                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.
        // 接下来，就是去执行Spring容器里面的一些PostProcessor了。
        // 先执行实现了PriorityOrdered接口的，然后是Ordered接口的，最后执行剩下的
        List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();

        
    
        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);
        
        // 此处缓冲起来（需要注意的是，是排序后，再放进去的 这样是最好的）
        registryProcessors.addAll(currentRegistryProcessors);

        
        invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
        // 此处把当前持有的执行对象给清空了，需要注意。以方便装载后续执行的处理器们
        currentRegistryProcessors.clear();

        // Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
        // 此处逻辑完全同上  处理实现Order接口的RegistryProcessors
        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();

        // Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
        // 最后执行，两个排序接口都没有实现的BeanDefinitionRegistryPostProcessor们，并且也缓存起来
        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;
                }
            }
            sortPostProcessors(currentRegistryProcessors, beanFactory);
            registryProcessors.addAll(currentRegistryProcessors);
            invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
            currentRegistryProcessors.clear();
        }

    
        invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
        invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
    } else {
        // Invoke factory processors registered with the context instance.
        // 若是普通的Bean工厂，就直接执行set进来的后置处理器即可（因为容器里就没有其它Bean定义了）
        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!
    // 下面就是开始执行BeanFactoryPostProcessor 基本也是按照上面的顺序来执行的
    // 执行使用配置注册的
    String[] postProcessorNames =
            beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

    // Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
    // Ordered, and the rest.
    List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
    List<String> orderedPostProcessorNames = new ArrayList<>();
    List<String> nonOrderedPostProcessorNames = new ArrayList<>();
    for (String ppName : postProcessorNames) {

        // 这里面注意，已经执行过的后置处理器，就不要再执行了
        if (processedBeans.contains(ppName)) {
            // skip - already processed in first phase above
        }
        else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
            priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
        }
        else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
            orderedPostProcessorNames.add(ppName);
        }
        else {
            nonOrderedPostProcessorNames.add(ppName);
        }
    }

    // First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
    sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
    invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

    // Next, invoke the BeanFactoryPostProcessors that implement Ordered.
    List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>();
    for (String postProcessorName : orderedPostProcessorNames) {
        orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
    }
    sortPostProcessors(orderedPostProcessors, beanFactory);
    invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);

    // Finally, invoke all other BeanFactoryPostProcessors.
    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();
}

这里核心就是调用手动添加到 ApplicationContext 中的 BeanFactoryPostProcessor 和使用配置注册到 BeanFactory 的处理器。

但是同时要处理两个问题：

• BeanFactoryPostProcessor 的顺序问题(实现了PriorityOrdered > 实现了Ordered > 什么都没实现)
• 对于 BeanDefinitionRegistryPostProcessor 的处理,在这里面可以动态修改或者增加 BeanDefinition

6 registerBeanPostProcessors(beanFactory)

注册 BeanPostProcessor

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

重点戏还是在 PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, this)

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

    // 从所与Bean定义中提取出BeanPostProcessor类型的Bean
   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.
    // BeanFactory中BeanPostProcessor的总数
   int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
    // 先注册一个BeanPostProcessorChecker
    // 这个有什么用呢，下面我会说明
   beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

   // Separate between BeanPostProcessors that implement PriorityOrdered,
   // Ordered, and the rest.
    // 先按优先级，归类了BeanPostProcessor
   List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
   List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
   List<String> orderedPostProcessorNames = new ArrayList<>();
   List<String> nonOrderedPostProcessorNames = new ArrayList<>();
   for (String ppName : postProcessorNames) {
      if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
         BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
         priorityOrderedPostProcessors.add(pp);
         if (pp instanceof MergedBeanDefinitionPostProcessor) {
            internalPostProcessors.add(pp);
         }
      }
      else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
         orderedPostProcessorNames.add(ppName);
      }
      else {
         nonOrderedPostProcessorNames.add(ppName);
      }
   }

   // First, register the BeanPostProcessors that implement PriorityOrdered.
   sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
   registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

   // Next, register the BeanPostProcessors that implement 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);

   // Now, register all regular BeanPostProcessors.
   List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<>();
   for (String ppName : nonOrderedPostProcessorNames) {
      BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
      nonOrderedPostProcessors.add(pp);
      if (pp instanceof MergedBeanDefinitionPostProcessor) {
         internalPostProcessors.add(pp);
      }
   }
   registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);

   // Finally, re-register all internal BeanPostProcessors.
   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).
    // 把ApplicationListenerDetector 移动到最后
   beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}

这里我们获取到了 BeanFactory 中定义的所有的 BeanPostProcessor 对象，并添加到 AbstractBeanFactory 中的 List<BeanPostProcessor> beanPostProcessors 中，以便后面创建bean的时候调用

这里有一个BeanPostProcessorChecker，这里是为了检测创建Bean的时候是否所有的BeanPostProcessor都已经注册好。

7 initMessageSource()

这部分逻辑比较简单：向容器里注册一个一个事件源的单例Bean： MessageSource

8 initApplicationEventMulticaster()

初始化Spring的事件多播器： ApplicationEventMulticaster

protected void initApplicationEventMulticaster() {
        ConfigurableListableBeanFactory beanFactory = getBeanFactory();
        if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {
            this.applicationEventMulticaster = beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);
        } else {
            this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory);
            beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, this.applicationEventMulticaster); 
        }
    }

检测用户是否自定义，没有就创建默认的

9 onRefresh()

一个模板方法，留给子类实现

10 registerListeners()

上面的过程已经注册好了事件多播器，现在注册监听器

protected void registerListeners() {
    
        for (ApplicationListener<?> listener : getApplicationListeners()) {
            // 把手动注册的监听器绑定到广播器
            getApplicationEventMulticaster().addApplicationListener(listener);
        }

        // Do not initialize FactoryBeans here: We need to leave all regular beans
        // uninitialized to let post-processors apply to them!
        // 取到容器里面的所有的监听器的名称，绑定到广播器  后面会广播出去这些事件的
        String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);
        for (String listenerBeanName : listenerBeanNames) {
            getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);
        }

        // Publish early application events now that we finally have a multicaster...
        // 如果存在早期应用事件，这里就直接发布了(同时就把earlyApplicationEvents该字段置为null)
        Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;
        this.earlyApplicationEvents = null;
        if (earlyEventsToProcess != null) {
            for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
                getApplicationEventMulticaster().multicastEvent(earlyEvent);
            }
        }
    }

11 finishBeanFactoryInitialization(beanFactory)

实例化所有单例的非懒加载的Bean,并完成依赖注入，这里有点复杂

protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
   // 初始化上下文的转换服务，ConversionService是一个类型转换接口
   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.
   if (!beanFactory.hasEmbeddedValueResolver()) {
      beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
   }

   // 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);
   }

   // 停止使用临时的类加载器
   beanFactory.setTempClassLoader(null);

   // 缓存（冻结）所有的bean definition数据，不期望以后会改变
   beanFactory.freezeConfiguration();

   // 重要的方法  实例化所有剩余的单例Bean
   beanFactory.preInstantiateSingletons();
}

接下来就看这个重要的方法 DefaultListableBeanFactory#preInstantiateSingletons

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

        // 获取所有的beanName
        List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);

        // 初始化所有的非懒加载的单例bean
        for (String beanName : beanNames) {
            RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
            // 不是抽象类， 是单例的，不是懒加载的
            if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
                // 如果是工厂Bean，那就会此工厂Bean放进去
                if (isFactoryBean(beanName)) {
                    final FactoryBean<?> factory = (FactoryBean<?>) getBean(FACTORY_BEAN_PREFIX + beanName);
                    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);
                    }
                }
                else {
                    // 非FactoryBean初始化
                    getBean(beanName);
                }
            }
        }

        // Trigger post-initialization callback for all applicable beans...
        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();
                }
            }
        }
    }

这里面通过 FactoryBean 定义的，它是懒加载的

创建Bean-getBean(beanName)方法

这里就是对于Bean的依赖的解析，完成Bean的创建，然后对Bean中的属性完成注入。

由于这里内容较多，我们就放到下一次在总结。

12 finishRefresh()

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);
}

refresh完成后的一些处理

初始化声明周期方法，发布事件等等