Spring源码：registerBeanPostProcessors源码解析

registerBeanPostProcessors源码解析

将自身需要的BeanPostProcessor和扫描得到的处理器，注册到Bean工厂，此时Bean后置处理器并不执行，而是放在实例化Bean之前执行

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

   //找出所有实现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工厂本身需要的BeanPostProcessor和自己注册的BeanPostProcessor
   int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
   beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));


   // Separate between BeanPostProcessors that implement PriorityOrdered,
   // Ordered, and the rest.
   //分离那些实现了PriorityOrdered, Ordered接口与其余接口的Bean后置处理器
   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：注册（添加到工厂）实现了PriorityOrdered接口的Bean后置处理器
   sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
   //将实现了这个接口的BeanPostProcessor存入（注册）this.BeanPostProcessors中
   registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);


   // Next, register the BeanPostProcessors that implement Ordered.
   //第二步：注册注册（添加到工厂）实现了Ordered接口的Bean后置处理器
   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.
   //现在，注册所有常规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.
   //最后，再次注册所有内部BeanPostProcessor，将相同的BeanPostProcessors放在处理链尾。
   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).
   //再次注册用于将内部bean检测为ApplicationListener的后处理器
   //将其移动到处理器链的末尾（用于拾取代理等）。
   beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}