Spring启动流程refresh()源码深入解析

一、Spring容器的refresh()

spring  version:4.3.12  ，尚硅谷Spring注解驱动开发—源码部分

//refresh():543, AbstractApplicationContext (org.springframework.context.support) 
public void refresh() throws BeansException, IllegalStateException {
 synchronized (this.startupShutdownMonitor) {
  //1 刷新前的预处理
  prepareRefresh();
  //2 获取BeanFactory；刚创建的默认DefaultListableBeanFactory
  ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
  //3 BeanFactory的预准备工作（BeanFactory进行一些设置）
  prepareBeanFactory(beanFactory);
​
  try {
  // 4 BeanFactory准备工作完成后进行的后置处理工作；
   // 4.1）、抽象的方法，当前未做处理。子类通过重写这个方法来在BeanFactory创建并预准备完成以后做进一步的设置
  postProcessBeanFactory(beanFactory); 
 
  
  // 5 执行BeanFactoryPostProcessor的方法；
//BeanFactoryPostProcessor：BeanFactory的后置处理器。在BeanFactory标准初始化之后执行的；
//他的重要两个接口：BeanFactoryPostProcessor、BeanDefinitionRegistryPostProcessor
  invokeBeanFactoryPostProcessors(beanFactory);
​
  //6 注册BeanPostProcessor（Bean的后置处理器）
  registerBeanPostProcessors(beanFactory);
​
  // 7 initMessageSource();初始化MessageSource组件（做国际化功能；消息绑定，消息解析）；
  initMessageSource();
​
  // 8 初始化事件派发器
  initApplicationEventMulticaster();
​
  // 9 子类重写这个方法，在容器刷新的时候可以自定义逻辑；
  onRefresh();
​
  // 10 给容器中将所有项目里面的ApplicationListener注册进来
 
  registerListeners();
 
​
  // 11.初始化所有剩下的单实例bean；
  finishBeanFactoryInitialization(beanFactory);
​
  // 12.完成BeanFactory的初始化创建工作；IOC容器就创建完成；
  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();
  }
 }
 }

1 、prepareRefresh()刷新前的预处理;

//刷新前的预处理;
protected void prepareRefresh() {
 this.startupDate = System.currentTimeMillis();
 this.closed.set(false);
 this.active.set(true);
​
 if (logger.isInfoEnabled()) {
 logger.info("Refreshing " + this);
 }
 // 初始化一些属性设置;子类自定义个性化的属性设置方法；
 initPropertySources(); 
 // 校验配置文件的属性，合法性
 getEnvironment().validateRequiredProperties();
 //保存容器中的一些事件
 this.earlyApplicationEvents = new linkedHashSet();
}

2、 obtainFreshBeanFactory();创建了一个BeanFactory

protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
 refreshBeanFactory(); //创建了一个this.beanFactory = new DefaultListableBeanFactory();设置了序列化的ID
 //返回刚才创建的DefaultListableBeanFactory
 ConfigurableListableBeanFactory beanFactory = getBeanFactory();
 if (logger.isDebugEnabled()) {
 logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
 }
 return beanFactory;
}

3、 BeanFactory的预准备工作

protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
 // 1）、设置BeanFactory的类加载器
 beanFactory.setBeanClassLoader(getClassLoader());
 // 1）、设置支持表达式解析器
 beanFactory.setBeanexpressionResolver(new StandardBeanexpressionResolver(beanFactory.getBeanClassLoader()));
 beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));
​
 // 2）、添加部分BeanPostProcessor【ApplicationContextAwareProcessor】
 beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
 // 3）、设置忽略的自动装配的接口EnvironmentAware、EmbeddedValueResolverAware、xxx；
 // 这些接口的实现类不能通过类型来自动注入
 beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
 beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
 beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
 beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
 beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
 beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);
​
 // 4）、注册可以解析的自动装配；我们能直接在任何组件中自动注入：
 //BeanFactory、ResourceLoader、ApplicationEventPublisher、ApplicationContext
 
 beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
 beanFactory.registerResolvableDependency(ResourceLoader.class, this);
 beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
 beanFactory.registerResolvableDependency(ApplicationContext.class, this);
​
 // 5）、添加BeanPostProcessor【ApplicationListenerDetector】后置处理器，在bean初始化前后的一些工作
 beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));
​
 // 6）、添加编译时的AspectJ；
 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()));
 }
​
 // 7）、给BeanFactory中注册一些能用的组件；
 if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) {
 // 环境信息ConfigurableEnvironment
 beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
 }
 //系统属性，systemProperties【Map】
 if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) {
 beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());
 }
 //系统环境变量systemEnvironment【Map】
 if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) {
 beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());
 }
}

5 执行BeanFactoryPostProcessor的后置处理器方法（BeanFactory）；

protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
 //执行BeanFactoryPostProcessor的方法
 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()));
 }
}

5.1    执行invokeBeanFactoryPostProcessors

public static void invokeBeanFactoryPostProcessors(
 ConfigurableListableBeanFactory beanFactory, List beanFactoryPostProcessors) {
​
 // Invoke BeanDefinitionRegistryPostProcessors first, if any.
 Set processedBeans = new HashSet();
 // 判断beanFatory类型
 if (beanFactory instanceof BeanDefinitionRegistry) {
 BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
 List regularPostProcessors = new linkedList();
 List registryProcessors = new linkedList();
 //得到所有的BeanFactoryPostProcessor 遍历
 for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
  if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
  BeanDefinitionRegistryPostProcessor registryProcessor =
   (BeanDefinitionRegistryPostProcessor) postProcessor;
  registryProcessor.postProcessBeanDefinitionRegistry(registry);
  registryProcessors.add(registryProcessor);
  }
  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 currentRegistryProcessors = new ArrayList();
​
 
 //从容器中获取所有的BeanDefinitionRegistryPostProcessor，
 String[] postProcessorNames =
  beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
 // 第一步，先执行实现了PriorityOrdered接口的BeanDefinitionRegistryPostProcessor
 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的 postProcessor.postProcessBeanDefinitionRegistry(registry)
 invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
 currentRegistryProcessors.clear();
​
 // 在执行实现了Ordered顺序接口的BeanDefinitionRegistryPostProcessor；
 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postProcessor.postProcessBeanDefinitionRegistry(registry)
 invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
 currentRegistryProcessors.clear();
​
 // 最后执行没有实现任何优先级或者是顺序接口的BeanDefinitionRegistryPostProcessors；
 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();
 }
​
 // 现在执行 BeanFactoryPostProcessor的postProcessBeanFactory()方法
 invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
 invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
 }
​
 else {
 // Invoke factory processors registered with the context instance.
 invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
 }
​
 //再执行BeanFactoryPostProcessor的方法
 //1）、获取所有的BeanFactoryPostProcessor 和执行BeanDefinitionRegistryPostProcessors的接口逻辑一样
 String[] postProcessorNames =
 beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);
​
 
 List priorityOrderedPostProcessors = new ArrayList();
 List orderedPostProcessorNames = new ArrayList();
 List nonOrderedPostProcessorNames = new ArrayList();
 //把BeanFactoryPostProcessor 分类
 for (String ppName : postProcessorNames) {
 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);
 }
 }
​
 // 2）、看先执行实现了PriorityOrdered优先级接口的BeanFactoryPostProcessor、
 sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
 invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);
​
 // 3）、在执行实现了Ordered顺序接口的BeanFactoryPostProcessor；
 List orderedPostProcessors = new ArrayList();
 for (String postProcessorName : orderedPostProcessorNames) {
 orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
 }
 sortPostProcessors(orderedPostProcessors, beanFactory);
 invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);
​
 // 4）、最后执行没有实现任何优先级或者是顺序接口的BeanFactoryPostProcessor；
 List nonOrderedPostProcessors = new ArrayList();
 for (String postProcessorName : nonOrderedPostProcessorNames) {
 nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
 }
 invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);
 beanFactory.clearmetadataCache();
}

6、注册BeanPostProcessor（Bean的后置处理器）

bean的创建拦截器

不同接口类型的BeanPostProcessor；在Bean创建前后的执行时机是不一样的

• BeanPostProcessor、
• DestructionAwareBeanPostProcessor、
• InstantiationAwareBeanPostProcessor、   在createBean()方法中处理的，bean创建之前调用的
• SmartInstantiationAwareBeanPostProcessor、
• MergedBeanDefinitionPostProcessor【internalPostProcessors】  （bean创建完成后调用，11章节中）

registerBeanPostProcessors(beanFactory);

​
public static void registerBeanPostProcessors(
 ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
//1）、获取所有的 BeanPostProcessor;后置处理器都默认可以通过PriorityOrdered、Ordered接口来执行优先级
 String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);
​
  //检查器，检查所有的BeanPostProcessor
 int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
 beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));
​
 // Separate between BeanPostProcessors that implement PriorityOrdered,
 // Ordered, and the rest.
 List priorityOrderedPostProcessors = new ArrayList();
 List internalPostProcessors = new ArrayList();
 List orderedPostProcessorNames = new ArrayList();
 List 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);
  }
 }
​
 
 sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
 registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);
​
 // 3）、再注册Ordered接口的
 List 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);
​
 // 4）、最后注册没有实现任何优先级接口的
 List 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);
​
 // 5）、最终注册MergedBeanDefinitionPostProcessor；
 sortPostProcessors(internalPostProcessors, beanFactory);
 registerBeanPostProcessors(beanFactory, internalPostProcessors);
​
 // 6）、注册一个ApplicationListenerDetector；判断创建完成的bean是否监听器
 
 beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}

7、initMessageSource();国际化

初始化MessageSource组件（做国际化功能；消息绑定，消息解析）；

​
protected void initMessageSource() {
 // 1）、获取BeanFactory
 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.isDebugEnabled()) {
   logger.debug("Using MessageSource [" + this.messageSource + "]");
  }
 }
 else {
  // 如果没有自己创建一个DelegatingMessageSource；
  DelegatingMessageSource dms = new DelegatingMessageSource();
  dms.setParentMessageSource(getInternalParentMessageSource());
  this.messageSource = dms;
  //把创建好的messageSource注册到容器中，以后获取国际化配置文件的值的时候，可以自动注入MessageSource； 
  //注入后通过这个方法使用MessageSource.getMessage(String code, Object[] args, String defaultMessage, Locale locale);
  beanFactory.registerSingleton(MESSAGE_SOURCE_BEAN_NAME, this.messageSource);
  if (logger.isDebugEnabled()) {
   logger.debug("Unable to locate MessageSource with name '" + MESSAGE_SOURCE_BEAN_NAME +
"': using default [" + this.messageSource + "]");
  }
 }
}

8、初始化事件派发器initApplicationEventMulticaster()

​
protected void initApplicationEventMulticaster() {
 //1）、获取BeanFactory
 ConfigurableListableBeanFactory beanFactory = getBeanFactory();
 //判断容器中是否有applicationEventMulticaster 的这个bean ,如果有获取，没有创建
 if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {
  //2）、从BeanFactory中获取applicationEventMulticaster的ApplicationEventMulticaster；
  this.applicationEventMulticaster =
   beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);
  if (logger.isDebugEnabled()) {
   logger.debug("Using ApplicationEventMulticaster [" + this.applicationEventMulticaster + "]");
  }
 }
 else {
  //3) 个SimpleApplicationEventMulticaster 类型的 applicationEventMulticaster
  this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory);
  //4）、将创建的ApplicationEventMulticaster添加到BeanFactory中，以后其他组件直接自动注入
  beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, this.applicationEventMulticaster);
  if (logger.isDebugEnabled()) {
   logger.debug("Unable to locate ApplicationEventMulticaster with name '" +
APPLICATION_EVENT_MULTICASTER_BEAN_NAME +
"': using default [" + this.applicationEventMulticaster + "]");
  }
 }
}

9、onRefresh();留给子容器（子类）

 1、子类重写AbstractApplicationContext.onRefresh()这个方法，在容器刷新的时候可以自定义逻辑；

10、registerListeners();检查和注册 Listener

将所有项目里面的ApplicationListener注册到容器中；

​
protected void registerListeners() {
 //1、从容器中拿到所有的ApplicationListener
 for (ApplicationListener listener : getApplicationListeners()) {
  //2、将每个监听器添加到事件派发器中；
  getApplicationEventMulticaster().addApplicationListener(listener);
 }
​
  
 // 1.获取所有的ApplicationListener
 String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);
 for (String listenerBeanName : listenerBeanNames) {
  //2、将每个监听器添加到事件派发器中；
  getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);
 }
​
 // earlyApplicationEvents 中保存之前的事件，
 Set earlyEventsToProcess = this.earlyApplicationEvents;
 this.earlyApplicationEvents = null;
 if (earlyEventsToProcess != null) {
  for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
   //3、派发之前步骤产生的事件；
   getApplicationEventMulticaster().multicastEvent(earlyEvent);
  }
 }
}

11、初始化所有剩下的单实例bean；finishBeanFactoryInitialization(beanFactory);

protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
 // 类型装换器
 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));
 }
​
 //值解析器
 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.
 beanFactory.freezeConfiguration();
​
 // 初始化剩下的单实例bean
 beanFactory.preInstantiateSingletons();
}

11.1 beanFactory.preInstantiateSingletons()初始化剩下的单实例bean

//preInstantiateSingletons():781, DefaultListableBeanFactory 
public void preInstantiateSingletons() throws BeansException {
 if (this.logger.isDebugEnabled()) {
  this.logger.debug("Pre-instantiating singletons in " + this);
 }
  //1）、获取容器中的所有Bean，依次进行初始化和创建对象 
 List beanNames = new ArrayList(this.beanDefinitionNames);
 for (String beanName : beanNames) {
  //2）、获取Bean的定义信息；RootBeanDefinition
  RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
  //3）、Bean不是抽象的，是单实例的，不是懒加载；
  if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
   // 3.1）、判断是否是FactoryBean；是否是实现FactoryBean接口的Bean；
   if (isFactoryBean(beanName)) {
    final FactoryBean factory = (FactoryBean) getBean(FACTORY_BEAN_PREFIX + beanName);
    boolean isEagerInit;
    if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
     isEagerInit = AccessController.doPrivileged(new PrivilegedAction() {
      @Override
      public Boolean run() {
return ((SmartFactoryBean) factory).isEagerInit();
      }
     }, getAccessControlContext());
    }
    else {
     isEagerInit = (factory instanceof SmartFactoryBean &&
  ((SmartFactoryBean) factory).isEagerInit());
    }
    if (isEagerInit) {
     getBean(beanName);
    }
   }
   else { //3.2）、不是工厂Bean。利用getBean(beanName);创建对象
    getBean(beanName); //详情请见 （11.1.3.2 创建bean ->doGetBean）章节
   }
  }
 }
​
 // 循环所有的bean 
 for (String beanName : beanNames) {
  Object singletonInstance = getSingleton(beanName);
  //判断bean是否实现了SmartInitializingSingleton 接口如果是；就执行afterSingletonsInstantiated()；
  if (singletonInstance instanceof SmartInitializingSingleton) {
   final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
   if (System.getSecurityManager() != null) {
    AccessController.doPrivileged(new PrivilegedAction