Spring invokeBeanFactoryPostProcessors方法刨析源码

	
	protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
		// 获取到当前应用程序上下文的beanFactoryPostProcessors变量的值，并且实例化调用执行所有已经注册的beanFactoryPostProcessor
		// 默认情况下，通过getBeanFactoryPostProcessors()来获取已经注册的BFPP，但是默认是空的 
		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()));
		}
	}

	public final ConfigurableListableBeanFactory getBeanFactory() {
		DefaultListableBeanFactory beanFactory = this.beanFactory;
		if (beanFactory == null) {
			throw new IllegalStateException("BeanFactory not initialized or already closed - " +
					"call 'refresh' before accessing beans via the ApplicationContext");
		}
		return beanFactory;
	}

if (beanFactory instanceof BeanDefinitionRegistry) {
...
}

invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);

  // 类型转换
  BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
  // 此处希望大家做一个区分，两个接口是不同的，BeanDefinitionRegistryPostProcessor是BeanFactoryPostProcessor的子集
  // BeanFactoryPostProcessor主要针对的操作对象是BeanFactory，而BeanDefinitionRegistryPostProcessor主要针对的操作对象是BeanDefinition
  // 存放BeanFactoryPostProcessor的集合
  List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
  // 存放BeanDefinitionRegistryPostProcessor的集合
  List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();
  // 首先处理入参中的beanFactoryPostProcessors,遍历所有的beanFactoryPostProcessors，将BeanDefinitionRegistryPostProcessor
  // 和BeanFactoryPostProcessor区分开
  for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
      // 如果是BeanDefinitionRegistryPostProcessor
      if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
          BeanDefinitionRegistryPostProcessor registryProcessor =
                  (BeanDefinitionRegistryPostProcessor) postProcessor;
          // 直接执行BeanDefinitionRegistryPostProcessor接口中的postProcessBeanDefinitionRegistry方法
          registryProcessor.postProcessBeanDefinitionRegistry(registry);
          // 添加到registryProcessors，用于后续执行postProcessBeanFactory方法
          registryProcessors.add(registryProcessor);
      } else {
          // 否则，只是普通的BeanFactoryPostProcessor，添加到regularPostProcessors，用于后续执行postProcessBeanFactory方法
          regularPostProcessors.add(postProcessor);
      }
  }

  List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();
  // First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
  // 调用所有实现PriorityOrdered接口的BeanDefinitionRegistryPostProcessor实现类
  // 找到所有实现BeanDefinitionRegistryPostProcessor接口bean的beanName
  String[] postProcessorNames =
          beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
  // 遍历处理所有符合规则的postProcessorNames
  for (String ppName : postProcessorNames) {
      // 检测是否实现了PriorityOrdered接口
      if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
          // 获取名字对应的bean实例，添加到currentRegistryProcessors中
          currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
          // 将要被执行的BFPP名称添加到processedBeans，避免后续重复执行
          processedBeans.add(ppName);
      }
  }
  // 按照优先级进行排序操作
  sortPostProcessors(currentRegistryProcessors, beanFactory);
  // 添加到registryProcessors中，用于最后执行postProcessBeanFactory方法
  registryProcessors.addAll(currentRegistryProcessors);
  // 遍历currentRegistryProcessors，执行postProcessBeanDefinitionRegistry方法
  invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
  // 执行完毕之后，清空currentRegistryProcessors
  currentRegistryProcessors.clear();

 postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
 for (String ppName : postProcessorNames) {
     // 检测是否实现了Ordered接口，并且还未执行过
     if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
         // 获取名字对应的bean实例，添加到currentRegistryProcessors中
         currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
         // 将要被执行的BFPP名称添加到processedBeans，避免后续重复执行
         processedBeans.add(ppName);
     }
 }
 // 按照优先级进行排序操作
 sortPostProcessors(currentRegistryProcessors, beanFactory);
 // 添加到registryProcessors中，用于最后执行postProcessBeanFactory方法
 registryProcessors.addAll(currentRegistryProcessors);
 // 遍历currentRegistryProcessors，执行postProcessBeanDefinitionRegistry方法
 invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
 // 执行完毕之后，清空currentRegistryProcessors
 currentRegistryProcessors.clear();

  // 最后，调用所有剩下的BeanDefinitionRegistryPostProcessors
  boolean reiterate = true;
  while (reiterate) {
      reiterate = false;
      // 找出所有实现BeanDefinitionRegistryPostProcessor接口的类
      postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
      // 遍历执行
      for (String ppName : postProcessorNames) {
          // 跳过已经执行过的BeanDefinitionRegistryPostProcessor
          if (!processedBeans.contains(ppName)) {
              // 获取名字对应的bean实例，添加到currentRegistryProcessors中
              currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
              // 将要被执行的BFPP名称添加到processedBeans，避免后续重复执行
              processedBeans.add(ppName);
              reiterate = true;
          }
      }
      // 按照优先级进行排序操作
      sortPostProcessors(currentRegistryProcessors, beanFactory);
      // 添加到registryProcessors中，用于最后执行postProcessBeanFactory方法
      registryProcessors.addAll(currentRegistryProcessors);
      // 遍历currentRegistryProcessors，执行postProcessBeanDefinitionRegistry方法
      invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
      // 执行完毕之后，清空currentRegistryProcessors
      currentRegistryProcessors.clear();
  }

  // 调用所有BeanDefinitionRegistryPostProcessor的postProcessBeanFactory方法
  invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
  // 最后，调用入参beanFactoryPostProcessors中的普通BeanFactoryPostProcessor的postProcessBeanFactory方法
  invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);

   // 到这里为止，入参beanFactoryPostProcessors和容器中的所有BeanDefinitionRegistryPostProcessor已经全部处理完毕，下面开始处理容器中
   // 所有的BeanFactoryPostProcessor
   // 可能会包含一些实现类，只实现了BeanFactoryPostProcessor，并没有实现BeanDefinitionRegistryPostProcessor接口，
   // 因为有processedBeans记录了上面处理的实现了BeanDefinitionRegistryPostProcessor的类，所以不会重复处理。
   String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);
   regularPostProcessors = new ArrayList();
   registryProcessors = new ArrayList();
   currentRegistryProcessors = new ArrayList();
   postProcessorNames = postProcessorNames;
   int var20 = postProcessorNames.length;
   String ppName;
   for(var9 = 0; var9 < var20; ++var9) {
       ppName = postProcessorNames[var9];
       if (!processedBeans.contains(ppName)) {
           if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
               regularPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
           } else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
               registryProcessors.add(ppName);
           } else {
               currentRegistryProcessors.add(ppName);
           }
       }
   }
   sortPostProcessors(regularPostProcessors, beanFactory);
   invokeBeanFactoryPostProcessors((Collection)regularPostProcessors, (ConfigurableListableBeanFactory)beanFactory);
   List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList();
   Iterator var21 = registryProcessors.iterator();
   while(var21.hasNext()) {
       String postProcessorName = (String)var21.next();
       orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
   }
   sortPostProcessors(orderedPostProcessors, beanFactory);
   invokeBeanFactoryPostProcessors((Collection)orderedPostProcessors, (ConfigurableListableBeanFactory)beanFactory);
   List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList();
   Iterator var24 = currentRegistryProcessors.iterator();
   while(var24.hasNext()) {
       ppName = (String)var24.next();
       nonOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
   }
   invokeBeanFactoryPostProcessors((Collection)nonOrderedPostProcessors, (ConfigurableListableBeanFactory)beanFactory);
   // 因为后置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();