Spring源碼：registerBeanPostProcessors源碼解析

registerBeanPostProcessors源碼解析

將自身需要的BeanPostProcessor和掃描得到的處理器，註冊到Bean工廠，此時Bean後置處理器並不執行，而是放在實例化Bean之前執行

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

   //找出所有實現BeanPostProcessor接口的Bean的beanName
   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.
   //得到bean工廠本身需要的BeanPostProcessor和自己註冊的BeanPostProcessor
   int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
   beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));


   // Separate between BeanPostProcessors that implement PriorityOrdered,
   // Ordered, and the rest.
   //分離那些實現了PriorityOrdered, Ordered接口與其餘接口的Bean後置處理器
   List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
   List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
   List<String> orderedPostProcessorNames = new ArrayList<>();
   List<String> nonOrderedPostProcessorNames = new ArrayList<>();
   for (String ppName : postProcessorNames) {
      if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
         BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
         priorityOrderedPostProcessors.add(pp);
         if (pp instanceof MergedBeanDefinitionPostProcessor) {
            internalPostProcessors.add(pp);
         }
      }
      else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
         orderedPostProcessorNames.add(ppName);
      }
      else {
         nonOrderedPostProcessorNames.add(ppName);
      }
   }


   // First, register the BeanPostProcessors that implement PriorityOrdered.
   //第一步：註冊（添加到工廠）實現了PriorityOrdered接口的Bean後置處理器
   sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
   //將實現了這個接口的BeanPostProcessor存入（註冊）this.BeanPostProcessors中
   registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);


   // Next, register the BeanPostProcessors that implement Ordered.
   //第二步：註冊註冊（添加到工廠）實現了Ordered接口的Bean後置處理器
   List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>();
   for (String ppName : orderedPostProcessorNames) {
      BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
      orderedPostProcessors.add(pp);
      if (pp instanceof MergedBeanDefinitionPostProcessor) {
         internalPostProcessors.add(pp);
      }
   }
   sortPostProcessors(orderedPostProcessors, beanFactory);
   registerBeanPostProcessors(beanFactory, orderedPostProcessors);


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


   // Finally, re-register all internal BeanPostProcessors.
   //最後，再次註冊所有內部BeanPostProcessor，將相同的BeanPostProcessors放在處理鏈尾。
   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).
   //再次註冊用於將內部bean檢測爲ApplicationListener的後處理器
   //將其移動到處理器鏈的末尾（用於拾取代理等）。
   beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}