本文章基于 Spring 5.3.15

Spring IOC 的核心是 AbstractApplicationContext 的 refresh 方法。

其中一共有 13 个主要方法，这里分析第 5 个：invokeBeanFactoryPostProcessors。

1 AbstractApplicationContext

1-1 执行 Bean 工厂的增强器

invokeBeanFactoryPostProcessors(beanFactory)

protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {    // 获取 Bean工厂 增强器    // 执行 Bean工厂 增强器    PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());    if (!NativeDetector.inNativeImage() && beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {      	beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));      	beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));    }}

1-2 获取 Bean工厂 增强器

getBeanFactoryPostProcessors()

/** * Bean 工厂增强器集合 */private final List
    
      beanFactoryPostProcessors = new ArrayList<>();public List
     
       getBeanFactoryPostProcessors() {   return this.beanFactoryPostProcessors;}
     
    

1-2 执行 Bean工厂 增强器

invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors())

2 PostProcessorRegistrationDelegate

public static void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory, List
    
      beanFactoryPostProcessors) {   Set
     
       processedBeans = new HashSet<>();   // 对 BeanDefinitionRegistry 类型的处理   if (beanFactory instanceof BeanDefinitionRegistry) {      BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;      List
      
        regularPostProcessors = new ArrayList<>();      List
       
         registryProcessors = new ArrayList<>();      // 硬编码注册的后处理器      for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {         if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {            BeanDefinitionRegistryPostProcessor registryProcessor = (BeanDefinitionRegistryPostProcessor) postProcessor;            // 有自定义的方法，需要先调用            registryProcessor.postProcessBeanDefinitionRegistry(registry);            registryProcessors.add(registryProcessor);         } else {            // 记录常规 BeanFactoryPostProcessor            regularPostProcessors.add(postProcessor);         }      }      List
        
          currentRegistryProcessors = new ArrayList<>();      // 首先，调用实现 PriorityOrdered 的 BeanDefinitionRegistryPostProcessor      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);         }      }      // 排序增强器      sortPostProcessors(currentRegistryProcessors, beanFactory);      registryProcessors.addAll(currentRegistryProcessors);      // 调用 Bean 定义注册表增强器      invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());      currentRegistryProcessors.clear();      // 其次，调用实现 Ordered 的 BeanDefinitionRegistryPostProcessors      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);         }      }      // 排序增强器      sortPostProcessors(currentRegistryProcessors, beanFactory);      registryProcessors.addAll(currentRegistryProcessors);      // 调用 Bean 定义注册表增强器      invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());      currentRegistryProcessors.clear();      // 最后, 调用所有其他 BeanDefinitionRegistryPostProcessor 直到不再出现      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;            }         }         // 排序增强器         sortPostProcessors(currentRegistryProcessors, beanFactory);         registryProcessors.addAll(currentRegistryProcessors);         // 调用 Bean 定义注册表增强器         invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());         currentRegistryProcessors.clear();      }      // 调用 Bean 工厂增强器      invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);      invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);   } else {      // 调用向上下文实例注册的工厂处理器      invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);   }   // 配置中读取的 BeanFactoryPostProcessor 的处理   String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);   // 将实现 PriorityOrdered、Ordered 和其余部分的 BeanFactoryPostProcessor 分开   List
         
           priorityOrderedPostProcessors = new ArrayList<>(); List
          
            orderedPostProcessorNames = new ArrayList<>(); List
           
             nonOrderedPostProcessorNames = new ArrayList<>(); // 对后处理器进行分类 for (String ppName : postProcessorNames) { if (processedBeans.contains(ppName)) { // 已经处理过则跳过 } 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); } } // 首先，调用实现 PriorityOrdered 的 BeanFactoryPostProcessor sortPostProcessors(priorityOrderedPostProcessors, beanFactory); invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory); // 接下来，调用实现 Ordered 的 BeanFactoryPostProcessors List
            
              orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size()); for (String postProcessorName : orderedPostProcessorNames) { orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class)); } sortPostProcessors(orderedPostProcessors, beanFactory); invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory); // 最后，调用所有其他 BeanFactoryPostProcessor List
             
               nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size()); for (String postProcessorName : nonOrderedPostProcessorNames) { nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class)); } invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory); // 清除元数据缓存，清除缓存的合并 bean 定义，因为后处理器可能已经修改了原始元数据，例如替换值中的占位符 beanFactory.clearMetadataCache();}
             
            
           
          
         
        
       
      
     
    

2-1 排序增强器

sortPostProcessors(currentRegistryProcessors, beanFactory)

private static void sortPostProcessors(List
     postProcessors, ConfigurableListableBeanFactory beanFactory) {   if (postProcessors.size() <= 1) {      return;   }   Comparator

2-1 调用 Bean 定义注册表增强器

invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup())

private static void invokeBeanDefinitionRegistryPostProcessors( Collection
     postProcessors, BeanDefinitionRegistry registry, ApplicationStartup applicationStartup) {   for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) {      StartupStep postProcessBeanDefRegistry = applicationStartup.start("spring.context.beandef-registry.post-process").tag("postProcessor", postProcessor::toString);      postProcessor.postProcessBeanDefinitionRegistry(registry);      postProcessBeanDefRegistry.end();   }}

2-1 清除元数据缓存

beanFactory.clearMetadataCache()

3 DefaultListableBeanFactory

public void clearMetadataCache() {   // 调用父类方法   super.clearMetadataCache();   this.mergedBeanDefinitionHolders.clear();   // 按类型清除缓存   clearByTypeCache();}

3-1 调用父类方法

super.clearMetadataCache()

4 AbstractBeanFactory

public void clearMetadataCache() {   this.mergedBeanDefinitions.forEach((beanName, bd) -> {      // 判断 Bean 是否有资格进行元数据缓存      if (!isBeanEligibleForMetadataCaching(beanName)) {         bd.stale = true;      }   });}

4-1 判断 Bean 是否有资格进行元数据缓存

private final Set
    
      alreadyCreated = Collections.newSetFromMap(new ConcurrentHashMap<>(256));protected boolean isBeanEligibleForMetadataCaching(String beanName) {   return this.alreadyCreated.contains(beanName);}
    

3 DefaultListableBeanFactory

3-1 按类型清除缓存

clearByTypeCache()

private void clearByTypeCache() {   this.allBeanNamesByType.clear();   this.singletonBeanNamesByType.clear();}