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源码分析之上下文构建

发表于 更新于 分类于 阅读次数： Valine：
本文字数： 46k 阅读时长 ≈ 42 分钟

源码分析之上下文构建

以ClassPathXmlApplicationContext为例来说明

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ApplicationContext context = new ClassPathXmlApplicationContext("spring-lifecycle.xml");

一个简单地创建ApplicationContext实例的方法，spring会做什么事呢？

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// this(new String[] {configLocation}, true, null);
// refresh为true，parent为null
public ClassPathXmlApplicationContext(String[] configLocations, boolean refresh, ApplicationContext parent)
      throws BeansException {

   super(parent);
      // 为上下文设置配置文件的位置
   setConfigLocations(configLocations);
   if (refresh) {
         // 调用org.springframework.context.support.AbstractApplicationContext#refresh，刷新上下文，进行IOC容器的初始化
      refresh();
   }
}

spring在初始化上下文的最重要的方法就是这个refresh()方法了

refresh方法

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public void refresh() throws BeansException, IllegalStateException {
  //容器重启同步监控锁，防止刷新进行到一半被重复执行
   synchronized (this.startupShutdownMonitor) {
      // 准备应用上下文，填充配置文件占位符，记录容器启动时间和启动状态
      prepareRefresh();

    
     // 刷新内部bean factory，即在子类中启动refreshBeanFactory()的地方，创建DefaultListableBeanFactory工厂，根据配置文件生成BeanDefinition，完成配置文件定义到注册表BeanDefinitionRegistry注册bean的流程，此时对象还未被创建
      ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

      // 对beanFactory进行功能填充，配置类加载器，定制特殊bean，添加BeanPostProcessor可供回调
      prepareBeanFactory(beanFactory);

      try {
        // 设置BeanFactory后置处理，工厂加载完配置，初始化之前回调PostProcessBeanFactory，作为工厂扩展功能，子类想在bean定义加载完成后，开始初始化上下文之前做一些特殊逻辑
         postProcessBeanFactory(beanFactory);

         // 调用BeanFactory的后置处理器，这些后处理器是在Bean定义中向容器注册的，如PropertyPlaceholderConfigurer就是在此处调用替换掉${}占位符的内容的
         invokeBeanFactoryPostProcessors(beanFactory);

         // 注册Bean的后置处理器，bean扩展:postProcessBeforeInitialization和postProcessAfterInitialization，分别在Bean初始化之前和初始化之后得到执行，如AutowiredAnnotationBeanPostProcessor实现@Autowired注解功能
         registerBeanPostProcessors(beanFactory);

         //初始化MessageSource对象，国际化
         initMessageSource();

         // 初始化上下文中的事件机制
         initApplicationEventMulticaster();

         // 初始化其他的特殊Bean，空方法，留给子类扩展
         onRefresh();

         // 注册监听器，检查监听Bean并且将这些Bean向容器注册
         registerListeners();

         // 实例化工厂注册表里所有的（non-lazy-init）单例bean，填充属性，初始化实例(调用init-method方法)，调用BeanPostProcessor对实例bean进行后置处理
         finishBeanFactoryInitialization(beanFactory);

         //  发布容器事件，完成刷新
         finishRefresh();
      }

      catch (BeansException ex) {
         
                 // 为防止资源占用，如果出现异常销毁已经创建好的单例bean
         destroyBeans();
                // 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...
         resetCommonCaches();
      }
   }
}

prepareRefresh初始化

容器初始化之前的初始化工作

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protected void prepareRefresh() {
   // Switch to active.
   this.closed.set(false);
   this.active.set(true);

   // Initialize any placeholder property sources in the context environment.
  // 初始化环境资源
   initPropertySources();

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

   // Allow for the collection of early ApplicationEvents,
   // to be published once the multicaster is available...
  // 创建监听器事件的集合
   this.earlyApplicationEvents = new LinkedHashSet<ApplicationEvent>();
}

obtainFreshBeanFactory创建BeanFactory

创建BeanFactory，实现BeanFactory的全部功能

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// org.springframework.context.support.AbstractApplicationContext#obtainFreshBeanFactory
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
      // org.springframework.context.support.AbstractRefreshableApplicationContext#refreshBeanFactory,关闭原始的beanFactory，并创建新的BeanFactory
   refreshBeanFactory();
      //返回创建的新工厂
   ConfigurableListableBeanFactory beanFactory = getBeanFactory();
   
   return beanFactory;
}

refreshBeanFactory

org.springframework.context.support.AbstractRefreshableApplicationContext#refreshBeanFactory方法，关闭原始的beanFactory，并创建新的BeanFactory

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protected final void refreshBeanFactory() throws BeansException {
  // 如果存在BeanFactory，则进行销毁并关闭该BeanFactory
   if (hasBeanFactory()) {
      destroyBeans();
      closeBeanFactory();
   }
   try {
     // 创建DefaultListableBeanFactory
      DefaultListableBeanFactory beanFactory = createBeanFactory();
      beanFactory.setSerializationId(getId());
     //设置一些属性值  容器是否允许对象覆盖allowBeanDefinitionOverriding，循环依赖allowCircularReferences
      customizeBeanFactory(beanFactory);
         // 读取xml配置文件,载入BeanDefinition信息，存储在beanDefinitionMap中
     // 在DefaultListableBeanFactory类中定义的private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<String, BeanDefinition>(256);
      loadBeanDefinitions(beanFactory);
      this.beanFactory = beanFactory;
   }
   catch (IOException ex) {
      throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
   }
}
createBeanFactory方法

实例化DefaultListableBeanFactory

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protected DefaultListableBeanFactory createBeanFactory() {
   return new DefaultListableBeanFactory(getInternalParentBeanFactory());
}

DefaultListableBeanFactory继承了AbstractAutowireCapableBeanFactory类，

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public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFactory
      implements ConfigurableListableBeanFactory, BeanDefinitionRegistry, Serializable
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public AbstractAutowireCapableBeanFactory() {
   super();
  // 忽略给定接口的自动装配功能，这些接口spring会进行特殊处理
   ignoreDependencyInterface(BeanNameAware.class);
   ignoreDependencyInterface(BeanFactoryAware.class);
   ignoreDependencyInterface(BeanClassLoaderAware.class);
}
loadBeanDefinitions方法

org.springframework.context.support.AbstractXmlApplicationContext#loadBeanDefinitions方法，读取xml配置文件,载入BeanDefinition信息，存储在beanDefinitionMap中

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protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
   // Create a new XmlBeanDefinitionReader for the given BeanFactory.
  // 进行XML配置文件读取的类
   XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);

   // Configure the bean definition reader with this context's
   // resource loading environment.
   beanDefinitionReader.setEnvironment(this.getEnvironment());
   beanDefinitionReader.setResourceLoader(this);
   beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));

   // Allow a subclass to provide custom initialization of the reader,
   // then proceed with actually loading the bean definitions.
   initBeanDefinitionReader(beanDefinitionReader);
  // 获取对XML文件的验证模式
  // 加载XML文件，并得到对应的Document
  // 根据返回的Document注册Bean，会循环调用loadBeanDefinitions方法->其内调用doLoadBeanDefinitions->调用registerBeanDefinitions
   loadBeanDefinitions(beanDefinitionReader);
}
registerBeanDefinitions

org.springframework.beans.factory.xml.XmlBeanDefinitionReader#registerBeanDefinitions方法来进行解析和注册BeanDefinitions

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public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
  // DefaultBeanDefinitionDocumentReader实例化BeanDefinitionDocumentReader
   BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
  // 记录统计前的BeanDefinition的加载个数
   int countBefore = getRegistry().getBeanDefinitionCount();
  // 1.createReaderContext方法会初始化NamespaceHandlerReslver
  // 2.registerBeanDefinitions加载及注册bean，调用org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader#doRegisterBeanDefinitions方法
   documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
  // 本次加载的BeanDefinition个数
   return getRegistry().getBeanDefinitionCount() - countBefore;
}

1.createReaderContext流程

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public XmlReaderContext createReaderContext(Resource resource) {
  // getNamespaceHandlerResolver方法会进行创建解析器createDefaultNamespaceHandlerResolver
   return new XmlReaderContext(resource, this.problemReporter, this.eventListener,
         this.sourceExtractor, this, getNamespaceHandlerResolver());
}

// getNamespaceHandlerResolver调用
protected NamespaceHandlerResolver createDefaultNamespaceHandlerResolver() {
  // 实例化DefaultNamespaceHandlerResolver，设置handlerMappingsLocation路径为META-INF/spring.handlers
        return new DefaultNamespaceHandlerResolver(getResourceLoader().getClassLoader());
    }

2.registerBeanDefinitions在进行xml读取注册

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// 处理xml前  空方法
preProcessXml(root);
// 2.1进行xml读取
parseBeanDefinitions(root, this.delegate);
// 处理xml后  空方法
postProcessXml(root);

2.1parseBeanDefinitions方法

在进行xml处理时，对于不同的标签会进行不同的处理

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protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {
  // 判断是不是默认命名空间的(http://www.springframework.org/schema/beans)
   if (delegate.isDefaultNamespace(root)) {
      NodeList nl = root.getChildNodes();
      for (int i = 0; i < nl.getLength(); i++) {
         Node node = nl.item(i);
         if (node instanceof Element) {
            Element ele = (Element) node;
           // 2.1.1.spring的默认标签，默认标签包含了import、alias、bean、beans
            if (delegate.isDefaultNamespace(ele)) {
              // 2.1.2.解析各个标签中的属性，属于xml解析范围，不在进行深入
               parseDefaultElement(ele, delegate);
            }
            else {
              // 自定义标签，如aop、mvc、tx等
               delegate.parseCustomElement(ele);
            }
         }
      }
   }
   else {
     // 自定义标签
      delegate.parseCustomElement(root);
   }
}

2.1.1 默认标签

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private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
   if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) { // import
      importBeanDefinitionResource(ele);
   }
   else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) { // alias
      processAliasRegistration(ele);
   }
   else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) { // bean
     // 2.1.1.1  进行bean注册
      processBeanDefinition(ele, delegate);
   }
   else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) { // beans
      // recurse
      doRegisterBeanDefinitions(ele);
   }
}

2.1.2 自定义标签

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public BeanDefinition parseCustomElement(Element ele) {
   return parseCustomElement(ele, null);
}

public BeanDefinition parseCustomElement(Element ele, BeanDefinition containingBd) {
  // 获取命名空间
        String namespaceUri = getNamespaceURI(ele);
  // 根据上述META-INF/spring.handlers文件进行映射，找到对应的handler，并进行初始化
        NamespaceHandler handler = this.readerContext.getNamespaceHandlerResolver().resolve(namespaceUri);
        if (handler == null) {
            
            return null;
        }
  // 进行解析
        return handler.parse(ele, new ParserContext(this.readerContext, this, containingBd));
    }

2.1.1.1 进行bean注册，根据beanName注册BeanDefinition

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public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
      throws BeanDefinitionStoreException {

   Assert.hasText(beanName, "Bean name must not be empty");
   Assert.notNull(beanDefinition, "BeanDefinition must not be null");

   if (beanDefinition instanceof AbstractBeanDefinition) {
      try {
        // 注册前的校验，主要是校验AbstractBeanDefinition属性中的methodOverrides和factoryMethodName
         ((AbstractBeanDefinition) beanDefinition).validate();
      }
      catch (BeanDefinitionValidationException ex) {
         throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
               "Validation of bean definition failed", ex);
      }
   }

   BeanDefinition oldBeanDefinition;
    // 从beanDefinitionMap中获取该beanName对应的实例
   oldBeanDefinition = this.beanDefinitionMap.get(beanName);
  // 如果该beanName已经注册过，需要进行处理
   if (oldBeanDefinition != null) {
     // 如果不允许覆盖则抛出异常
      if (!isAllowBeanDefinitionOverriding()) {
         throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
               "Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName +
               "': There is already [" + oldBeanDefinition + "] bound.");
      }
      else if (oldBeanDefinition.getRole() < beanDefinition.getRole()) {
         // e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE
         
      }
      else if (!beanDefinition.equals(oldBeanDefinition)) {
         
      }
      else {
         
      }
     // 进行覆盖
      this.beanDefinitionMap.put(beanName, beanDefinition);
   }
   else {
      if (hasBeanCreationStarted()) {
         // Cannot modify startup-time collection elements anymore (for stable iteration)
        // 防止map并发修改
         synchronized (this.beanDefinitionMap) {
            this.beanDefinitionMap.put(beanName, beanDefinition);
            List<String> updatedDefinitions = new ArrayList<String>(this.beanDefinitionNames.size() + 1);
            updatedDefinitions.addAll(this.beanDefinitionNames);
            updatedDefinitions.add(beanName);
            this.beanDefinitionNames = updatedDefinitions;
            if (this.manualSingletonNames.contains(beanName)) {
               Set<String> updatedSingletons = new LinkedHashSet<String>(this.manualSingletonNames);
               updatedSingletons.remove(beanName);
               this.manualSingletonNames = updatedSingletons;
            }
         }
      }
      else {
         // Still in startup registration phase
         this.beanDefinitionMap.put(beanName, beanDefinition);
         this.beanDefinitionNames.add(beanName);
         this.manualSingletonNames.remove(beanName);
      }
      this.frozenBeanDefinitionNames = null;
   }

   if (oldBeanDefinition != null || containsSingleton(beanName)) {
      resetBeanDefinition(beanName);
   }
}

prepareBeanFactory功能填充

对beanFactory的功能扩展

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protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
   // Tell the internal bean factory to use the context's class loader etc.
  // 设置类加载器
   beanFactory.setBeanClassLoader(getClassLoader());
  // 设置beanFactory的表达式语言处理器SPEL
   beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
  // 设置PropertyEditor属性编辑器
   beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));

  // 添加ApplicationContextAwareProcessor处理器  invokeAwareInterfaces方法，用于在前置处理器中执行EnvironmentAware#setEnvironment，EmbeddedValueResolverAware#setEmbeddedValueResolver，ResourceLoaderAware#setResourceLoader，ApplicationEventPublisherAware#setApplicationEventPublisher，MessageSourceAware#setMessageSource，ApplicationContextAware#setApplicationContext
   // Configure the bean factory with context callbacks.
   beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
  // 设置忽略自动装配的几个接口
   beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
   beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
   beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
   beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
   beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
   beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);

   // 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
   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.
  // 添加BeanPostProcessor
   beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));

  // 增加对AspectJ的支持
   // 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()));
   }

  // 注册默认的系统环境bean
   // Register default environment beans.
   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());
   }
}

BeanFactory 后处理器

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// Allows post-processing of the bean factory in context subclasses.
// 注册beanFactory后处理器
postProcessBeanFactory(beanFactory);

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

invokeBeanFactoryPostProcessors

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

   // Invoke BeanDefinitionRegistryPostProcessors first, if any.
   Set<String> processedBeans = new HashSet<String>();
// 对BeanDefinitionRegistry进行处理
   if (beanFactory instanceof BeanDefinitionRegistry) {
      BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
      List<BeanFactoryPostProcessor> regularPostProcessors = new LinkedList<BeanFactoryPostProcessor>();
      List<BeanDefinitionRegistryPostProcessor> registryProcessors = new LinkedList<BeanDefinitionRegistryPostProcessor>();
            // 注册BeanFactoryPostProcessor后处理器
      for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
         if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
            BeanDefinitionRegistryPostProcessor registryProcessor =
                  (BeanDefinitionRegistryPostProcessor) postProcessor;
           // BeanDefinitionRegistryPostProcessor类型的后处理器，需要进行特殊处理，先调用postProcessBeanDefinitionRegistry方法
            registryProcessor.postProcessBeanDefinitionRegistry(registry);
            registryProcessors.add(registryProcessor);
         }
         else {
           // 常规的BeanFactoryPostProcessor
            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<BeanDefinitionRegistryPostProcessor>();

      // First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
     // 执行 BeanDefinitionRegistryPostProcessor类型的后处理器
      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);
      registryProcessors.addAll(currentRegistryProcessors);
     // 执行BeanDefinitionRegistryPostProcessor#postProcessBeanDefinitionRegistry
      invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
      currentRegistryProcessors.clear();

      // Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
     // 执行 BeanDefinitionRegistryPostProcessor类型的后处理器
      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);
      registryProcessors.addAll(currentRegistryProcessors);
     // 执行BeanDefinitionRegistryPostProcessor#postProcessBeanDefinitionRegistry
      invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
      currentRegistryProcessors.clear();

      // Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
     // 执行BeanDefinitionRegistryPostProcessor类型后处理器
      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);
         registryProcessors.addAll(currentRegistryProcessors);
        // 执行BeanDefinitionRegistryPostProcessor#postProcessBeanDefinitionRegistry
         invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
         currentRegistryProcessors.clear();
      }

      // Now, invoke the postProcessBeanFactory callback of all processors handled so far.
     // 执行postProcessBeanFactory#postProcessBeanFactory
      invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
      invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
   }

   else {
      // Invoke factory processors registered with the context instance.
      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!
   String[] postProcessorNames =
         beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

   // Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
   // Ordered, and the rest.
   List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
   List<String> orderedPostProcessorNames = new ArrayList<String>();
   List<String> nonOrderedPostProcessorNames = new ArrayList<String>();
  // 进行分类，分别执行
   for (String ppName : postProcessorNames) {
      if (processedBeans.contains(ppName)) { // 已经处理过的
         // skip - already processed in first phase above
      }
      else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) { // 优先级的
         priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
      }
      else if (beanFactory.isTypeMatch(ppName, Ordered.class)) { // 排序的
         orderedPostProcessorNames.add(ppName);
      }
      else { // 没有顺序的
         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<BeanFactoryPostProcessor>();
   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<BeanFactoryPostProcessor>();
   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();
}

registerBeanPostProcessors注册BeanPostProcessor

注册bean的后处理器，调用是在bean实例化阶段调用的

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


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

        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;
  // BeanPostProcessorChecker 只是一个日志打印，如果spring的后处理器还没有开始注册就已经开始了bean初始化时，就会打印信息
        beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

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

        // First, register the BeanPostProcessors that implement PriorityOrdered.
  // 先注册所有实现了PriorityOrdered的BeanPostProcessors
        sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
        registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

        // Next, register the BeanPostProcessors that implement Ordered.
  // 注册所有实现了Ordered的BeanPostProcessors
        List<BeanPostProcessor> orderedPostProcessors = new ArrayList<BeanPostProcessor>();
        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.
  // 注册所有无序的BeanPostProcessor
        List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<BeanPostProcessor>();
        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).
        beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
    }

initMessageSource初始化消息资源

提取配置中定义的MessageSource，进行国际化的配置

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protected void initMessageSource() {
   ConfigurableListableBeanFactory beanFactory = getBeanFactory();
  // MESSAGE_SOURCE_BEAN_NAME = "messageSource"
   if (beanFactory.containsLocalBean(MESSAGE_SOURCE_BEAN_NAME)) { // 如果配置了messageSource
      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());
         }
      }
      
   }
   else { // 如果没有配置messageSource，会使用DelegatingMessageSource来作为messageSource
      // 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);
      
   }
}

initApplicationEventMulticaster事件广播

当出现事件时调用ApplicationEventMulticaster#multicastEvent调用invokeListener来执行监听器org.springframework.context.ApplicationListener#onApplicationEvent

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protected void initApplicationEventMulticaster() {
   ConfigurableListableBeanFactory beanFactory = getBeanFactory();
  //APPLICATION_EVENT_MULTICASTER_BEAN_NAME = "applicationEventMulticaster"
   if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) { // 自定义事件广播
      this.applicationEventMulticaster =
            beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);
      
   }
   else { // 没有自定义事件广播，使用默认的SimpleApplicationEventMulticaster
      this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory);
      beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, this.applicationEventMulticaster);
      
   }
}

registerListeners注册监听器

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protected void registerListeners() {
   // Register statically specified listeners first.
   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!
   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...
   Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;
   this.earlyApplicationEvents = null;
   if (earlyEventsToProcess != null) {
      for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
         getApplicationEventMulticaster().multicastEvent(earlyEvent);
      }
   }
}

finishBeanFactoryInitialization完成BeanFactory初始化

包括ConversionService的设置、非延迟加载的bean的初始化工作

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protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
   // Initialize conversion service for this context.
  // CONVERSION_SERVICE_BEAN_NAME = "conversionService"
  // ConversionService 自定义转换器
   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.
   if (!beanFactory.hasEmbeddedValueResolver()) {
      beanFactory.addEmbeddedValueResolver(new StringValueResolver() {
         @Override
         public String resolveStringValue(String strVal) {
            return 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);
   }

   // Stop using the temporary ClassLoader for type matching.
   beanFactory.setTempClassLoader(null);

   // Allow for caching all bean definition metadata, not expecting further changes.
  // 冻结所有的beanDefinition，不期待之后更改这些数据
   beanFactory.freezeConfiguration();

   // Instantiate all remaining (non-lazy-init) singletons.
  // 初始化剩下的非惰性的单例bean
   beanFactory.preInstantiateSingletons();
}

preInstantiateSingletons初始化bean

将bean进行实例化

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public void preInstantiateSingletons() throws BeansException {
   

   // 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<String>(this.beanDefinitionNames);

   // Trigger initialization of all non-lazy singleton beans...
   for (String beanName : beanNames) {
     // 拿到bean的定义信息
      RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
     // 非抽象的、单例的、非懒加载的
      if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
        // 是否FactoryBean,FactoryBean是通过调用getObject来进行创建对象的
         if (isFactoryBean(beanName)) {
            final FactoryBean<?> factory = (FactoryBean<?>) getBean(FACTORY_BEAN_PREFIX + beanName);
            boolean isEagerInit;
            
            isEagerInit = (factory instanceof SmartFactoryBean &&
                     ((SmartFactoryBean<?>) factory).isEagerInit());
            if (isEagerInit) {
               getBean(beanName);
            }
         }
         else {
           // getBean是实际创建bean实例的操作
            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;
         smartSingleton.afterSingletonsInstantiated();
         
      }
   }
}
getBean创建bean实例
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public Object getBean(String name) throws BeansException {
   return doGetBean(name, null, null, false);
}


protected <T> T doGetBean(
            final String name, final Class<T> requiredType, final Object[] args, boolean typeCheckOnly)
            throws BeansException {
        // 获取bean名称，主要是解决FactoryBean加的&前缀
        final String beanName = transformedBeanName(name);
        Object bean;

        // Eagerly check singleton cache for manually registered singletons.
  // 从缓存中获取
        Object sharedInstance = getSingleton(beanName);
        if (sharedInstance != null && args == null) {
        
            bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
        }

        else {
            // Fail if we're already creating this bean instance:
            // We're assumably within a circular reference.
            if (isPrototypeCurrentlyInCreation(beanName)) {
                throw new BeanCurrentlyInCreationException(beanName);
            }

            // Check if bean definition exists in this factory.
            BeanFactory parentBeanFactory = getParentBeanFactory();
            if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
                // Not found -> check parent.
                String nameToLookup = originalBeanName(name);
                if (args != null) {
                    // Delegation to parent with explicit args.
                    return (T) parentBeanFactory.getBean(nameToLookup, args);
                }
                else {
                    // No args -> delegate to standard getBean method.
                    return parentBeanFactory.getBean(nameToLookup, requiredType);
                }
            }

            if (!typeCheckOnly) {
                markBeanAsCreated(beanName);
            }

            try {
                final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
                checkMergedBeanDefinition(mbd, beanName, args);

                // Guarantee initialization of beans that the current bean depends on.
        // 当前bean是否有其他依赖bean，如果有，需要先加载
                String[] dependsOn = mbd.getDependsOn();
                if (dependsOn != null) {
                    for (String dep : dependsOn) {
                        if (isDependent(beanName, dep)) {
                            throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                                    "Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
                        }
                        registerDependentBean(dep, beanName);
                        try {
                            getBean(dep);
                        }
                        catch (NoSuchBeanDefinitionException ex) {
                            throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                                    "'" + beanName + "' depends on missing bean '" + dep + "'", ex);
                        }
                    }
                }

                // Create bean instance.
                if (mbd.isSingleton()) { // 单例
                    sharedInstance = getSingleton(beanName, new ObjectFactory<Object>() {
                        @Override
                        public Object getObject() throws BeansException {
                            try {
                                return createBean(beanName, mbd, args);
                            }
                            catch (BeansException ex) {
                                // Explicitly remove instance from singleton cache: It might have been put there
                                // eagerly by the creation process, to allow for circular reference resolution.
                                // Also remove any beans that received a temporary reference to the bean.
                                destroySingleton(beanName);
                                throw ex;
                            }
                        }
                    });
                    bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
                }

                else if (mbd.isPrototype()) { // 原型
                    // It's a prototype -> create a new instance.
                    Object prototypeInstance = null;
                    try {
                        beforePrototypeCreation(beanName);
                        prototypeInstance = createBean(beanName, mbd, args);
                    }
                    finally {
                        afterPrototypeCreation(beanName);
                    }
                    bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
                }

                else {
                    String scopeName = mbd.getScope();
                    final Scope scope = this.scopes.get(scopeName);
                    if (scope == null) {
                        throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");
                    }
                    try {
                        Object scopedInstance = scope.get(beanName, new ObjectFactory<Object>() {
                            @Override
                            public Object getObject() throws BeansException {
                                beforePrototypeCreation(beanName);
                                try {
                                    return createBean(beanName, mbd, args);
                                }
                                finally {
                                    afterPrototypeCreation(beanName);
                                }
                            }
                        });
                        bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
                    }
                    catch (IllegalStateException ex) {
                        throw new BeanCreationException(beanName,
                                "Scope '" + scopeName + "' is not active for the current thread; consider " +
                                "defining a scoped proxy for this bean if you intend to refer to it from a singleton",
                                ex);
                    }
                }
            }
            catch (BeansException ex) {
                cleanupAfterBeanCreationFailure(beanName);
                throw ex;
            }
        }

        // Check if required type matches the type of the actual bean instance.
        if (requiredType != null && bean != null && !requiredType.isInstance(bean)) {
            try {
                return getTypeConverter().convertIfNecessary(bean, requiredType);
            }
            catch (TypeMismatchException ex) {
                if (logger.isDebugEnabled()) {
                    logger.debug("Failed to convert bean '" + name + "' to required type '" +
                            ClassUtils.getQualifiedName(requiredType) + "'", ex);
                }
                throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
            }
        }
        return (T) bean;
    }
getSingleton(beanName)从缓存获取
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public Object getSingleton(String beanName) {
   return getSingleton(beanName, true);
}


protected Object getSingleton(String beanName, boolean allowEarlyReference) {
  // 从singletonObjects缓存中取
  // singletonObjects中存的是beanName和bean实例
  // singletonObjects是一级缓存
   Object singletonObject = this.singletonObjects.get(beanName);
  // 缓存中没有
   if (singletonObject == null && isSingletonCurrentlyInCreation(beanName)) {
     // 锁定全局变量进行处理
      synchronized (this.singletonObjects) {
        // 如果该bean正在进行加载则不进行处理，直接返回
        // earlySingletonObjects中存的是beanName和bean实例,但是与singletonObjects不同的是,存储的是还没进行属性注入操作的Bean的实例，，目的是为了监测循环引用
        // earlySingletonObjects是二级缓存
         singletonObject = this.earlySingletonObjects.get(beanName);
         if (singletonObject == null && allowEarlyReference) {
           // 从singletonFactories中获取，对于某些方法需要提前进行初始化时则会调用addSingletonFactory方法将对应的ObjectFactory初始化策略存在singletonFactories中
           // singletonFactories中存的是beanName和创建bean的ObjectFactory工厂
           // singletonFactories是三级缓存
            ObjectFactory<?> singletonFactory = this.singletonFactories.get(beanName);
            if (singletonFactory != null) {
              // 调用ObjectFactory的getObject方法
               singletonObject = singletonFactory.getObject();
              // 放入到二级缓存中
              // 记录在缓存earlySingletonObjects中，earlySingletonObjects和singletonFactories互斥，earlySingletonObjects与singletonObjects的不同之处在于当一个单例bean被放入该缓存后，那么其他的bean在创建过程中就能通过getBean方法获取到，目的是用来监测循环引用
               this.earlySingletonObjects.put(beanName, singletonObject);
               this.singletonFactories.remove(beanName);
            }
         }
      }
   }
   return (singletonObject != NULL_OBJECT ? singletonObject : null);
}
getSingleton(String beanName, ObjectFactory<?> singletonFactory)创建bean
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public Object getSingleton(String beanName, ObjectFactory<?> singletonFactory) {
   synchronized (this.singletonObjects) {
      Object singletonObject = this.singletonObjects.get(beanName);
      if (singletonObject == null) {
         if (this.singletonsCurrentlyInDestruction) {
            throw new BeanCreationNotAllowedException(beanName,
                  "Singleton bean creation not allowed while singletons of this factory are in destruction " +
                  "(Do not request a bean from a BeanFactory in a destroy method implementation!)");
         }
         
         beforeSingletonCreation(beanName);
         boolean newSingleton = false;
         boolean recordSuppressedExceptions = (this.suppressedExceptions == null);
         if (recordSuppressedExceptions) {
            this.suppressedExceptions = new LinkedHashSet<Exception>();
         }
         try {
           // 这里调用的就是createBean方法
            singletonObject = singletonFactory.getObject();
            newSingleton = true;
         }
         catch (IllegalStateException ex) {
            // Has the singleton object implicitly appeared in the meantime ->
            // if yes, proceed with it since the exception indicates that state.
            singletonObject = this.singletonObjects.get(beanName);
            if (singletonObject == null) {
               throw ex;
            }
         }
         catch (BeanCreationException ex) {
            
            throw ex;
         }
         finally {
            if (recordSuppressedExceptions) {
               this.suppressedExceptions = null;
            }
            afterSingletonCreation(beanName);
         }
         if (newSingleton) {
            addSingleton(beanName, singletonObject);
         }
      }
      return (singletonObject != NULL_OBJECT ? singletonObject : null);
   }
}
createBean创建bean

调用的是org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#createBean，其内实际调用的是doCreateBean

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protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args)
      throws BeanCreationException {

   // Instantiate the bean.
   BeanWrapper instanceWrapper = null;
   if (mbd.isSingleton()) {
      instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
   }
   if (instanceWrapper == null) {
     // 创建bean实例，但是未设置属性
      instanceWrapper = createBeanInstance(beanName, mbd, args);
   }
   final Object bean = (instanceWrapper != null ? instanceWrapper.getWrappedInstance() : null);
   Class<?> beanType = (instanceWrapper != null ? instanceWrapper.getWrappedClass() : null);
   mbd.resolvedTargetType = beanType;

   // Allow post-processors to modify the merged bean definition.
   synchronized (mbd.postProcessingLock) {
      if (!mbd.postProcessed) {
         try {
            applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);
         }
         catch (Throwable ex) {
            throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                  "Post-processing of merged bean definition failed", ex);
         }
         mbd.postProcessed = true;
      }
   }

   // Eagerly cache singletons to be able to resolve circular references
   // even when triggered by lifecycle interfaces like BeanFactoryAware.
   boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences &&
         isSingletonCurrentlyInCreation(beanName));
   if (earlySingletonExposure) {
      
      addSingletonFactory(beanName, new ObjectFactory<Object>() {
         @Override
         public Object getObject() throws BeansException {
            return getEarlyBeanReference(beanName, mbd, bean);
         }
      });
   }

   // Initialize the bean instance.
   Object exposedObject = bean;
   try {
     // 填充属性，上边实例化的时候只是默认属性
      populateBean(beanName, mbd, instanceWrapper);
      if (exposedObject != null) {
        // 1.调用 xxAware方法，BeanPostProcessor的前置处理postProcessBeforeInitialization，init-method，BeanPostProcessor的后置处理postProcessAfterInitialization
         exposedObject = initializeBean(beanName, exposedObject, mbd);
      }
   }
   catch (Throwable ex) {
      if (ex instanceof BeanCreationException && beanName.equals(((BeanCreationException) ex).getBeanName())) {
         throw (BeanCreationException) ex;
      }
      else {
         throw new BeanCreationException(
               mbd.getResourceDescription(), beanName, "Initialization of bean failed", ex);
      }
   }

   if (earlySingletonExposure) {
      Object earlySingletonReference = getSingleton(beanName, false);
      if (earlySingletonReference != null) {
         if (exposedObject == bean) {
            exposedObject = earlySingletonReference;
         }
         else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) {
            String[] dependentBeans = getDependentBeans(beanName);
            Set<String> actualDependentBeans = new LinkedHashSet<String>(dependentBeans.length);
            for (String dependentBean : dependentBeans) {
               if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) {
                  actualDependentBeans.add(dependentBean);
               }
            }
            if (!actualDependentBeans.isEmpty()) {
               throw new BeanCurrentlyInCreationException(beanName,
                     "Bean with name '" + beanName + "' has been injected into other beans [" +
                     StringUtils.collectionToCommaDelimitedString(actualDependentBeans) +
                     "] in its raw version as part of a circular reference, but has eventually been " +
                     "wrapped. This means that said other beans do not use the final version of the " +
                     "bean. This is often the result of over-eager type matching - consider using " +
                     "'getBeanNamesForType' with the 'allowEagerInit' flag turned off, for example.");
            }
         }
      }
   }

   // Register bean as disposable.
   try {
      registerDisposableBeanIfNecessary(beanName, bean, mbd);
   }
   catch (BeanDefinitionValidationException ex) {
      throw new BeanCreationException(
            mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
   }

   return exposedObject;
}

1.initializeBean

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protected Object initializeBean(final String beanName, final Object bean, RootBeanDefinition mbd) {
   // 调用 xxAware方法，
      invokeAwareMethods(beanName, bean);

   Object wrappedBean = bean;
   if (mbd == null || !mbd.isSynthetic()) {
     // BeanPostProcessor的前置处理postProcessBeforeInitialization，
      wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
   }

   try {
     // init-method，
      invokeInitMethods(beanName, wrappedBean, mbd);
   }
   catch (Throwable ex) {
      throw new BeanCreationException(
            (mbd != null ? mbd.getResourceDescription() : null),
            beanName, "Invocation of init method failed", ex);
   }
   if (mbd == null || !mbd.isSynthetic()) {
     // BeanPostProcessor的后置处理postProcessAfterInitialization,AOP动态代理在此处
      wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
   }
   return wrappedBean;
}

finishRefresh完成

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protected void finishRefresh() {
   // Initialize lifecycle processor for this context.
  // 初始化LifecycleProcessor
   initLifecycleProcessor();

   // Propagate refresh to lifecycle processor first.
  // 执行所有LifecycleProcessor的onRefresh方法
   getLifecycleProcessor().onRefresh();

   // Publish the final event.
  // 发布ContextRefreshedEvent事件
   publishEvent(new ContextRefreshedEvent(this));

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