工作内容

注册拦截 bean 创建的处理器。
这个过程和 IOC 容器启动过程 4-postProcessBeanFactory () 中的用户扩展很类似。
这里的扩展点影响 bean 的实例化操作。 

  1. public static void registerBeanPostProcessors(
  2.             ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
  4.         String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);
  6.         // Register BeanPostProcessorChecker that logs an info message when
  7.         // a bean is created during BeanPostProcessor instantiation, i.e. when
  8.         // a bean is not eligible for getting processed by all BeanPostProcessors.
  9.         int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
  10.         beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));
  12.         // Separate between BeanPostProcessors that implement PriorityOrdered,
  13.         // Ordered, and the rest.
  14.         List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
  15.         List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
  16.         List<String> orderedPostProcessorNames = new ArrayList<>();
  17.         List<String> nonOrderedPostProcessorNames = new ArrayList<>();
  18.         for (String ppName : postProcessorNames) {
  19.             if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
  20.                 BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
  21.                 priorityOrderedPostProcessors.add(pp);
  22.                 if (pp instanceof MergedBeanDefinitionPostProcessor) {
  23.                     internalPostProcessors.add(pp);
  24.                 }
  25.             } else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
  26.                 orderedPostProcessorNames.add(ppName);
  27.             } else {
  28.                 nonOrderedPostProcessorNames.add(ppName);
  29.             }
  30.         }
  32.         // First, register the BeanPostProcessors that implement PriorityOrdered.
  33.         sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
  34.         registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);
  36.         // Next, register the BeanPostProcessors that implement Ordered.
  37.         List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
  38.         for (String ppName : orderedPostProcessorNames) {
  39.             BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
  40.             orderedPostProcessors.add(pp);
  41.             if (pp instanceof MergedBeanDefinitionPostProcessor) {
  42.                 internalPostProcessors.add(pp);
  43.             }
  44.         }
  45.         sortPostProcessors(orderedPostProcessors, beanFactory);
  46.         registerBeanPostProcessors(beanFactory, orderedPostProcessors);
  48.         // Now, register all regular BeanPostProcessors.
  49.         List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
  50.         for (String ppName : nonOrderedPostProcessorNames) {
  51.             BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
  52.             nonOrderedPostProcessors.add(pp);
  53.             if (pp instanceof MergedBeanDefinitionPostProcessor) {
  54.                 internalPostProcessors.add(pp);
  55.             }
  56.         }
  57.         registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);
  59.         // Finally, re-register all internal BeanPostProcessors.
  60.         sortPostProcessors(internalPostProcessors, beanFactory);
  61.         registerBeanPostProcessors(beanFactory, internalPostProcessors);
  63.         // Re-register post-processor for detecting inner beans as ApplicationListeners,
  64.         // moving it to the end of the processor chain (for picking up proxies etc).
  65.         beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
  66.     }

主要流程

阶段1-查找BeanPostProcessor

  1. // 查找所有实现了BeanPostProcessor的bean，得到名称的集合
  2. String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);

阶段2-注册一个记录日志的BeanPostProcessor

  1. /**
  2.  * 注册的一个BeanPostProcessorChecker，用来记录写日志信息
  3.  */
  4. int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
  5. beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

这里面有个beanProcessorTargetCount计数，它的来源分为三个部分：

  • beanFactory.getBeanPostProcessorCount()：这些来自prepareBeanFactory阶段注册的
  • +1 ： 这是下面要注册的一个BeanPostProcessorChecker，用来记录写日志信息
  • postProcessorNames.length：这些就是我们自己通过接口注册的

    阶段3-分组 BeanPostProcessor

    根据优先级的接口分组
    1. List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
    2.       List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
    3.       List<String> orderedPostProcessorNames = new ArrayList<>();
    4.       List<String> nonOrderedPostProcessorNames = new ArrayList<>();
    5.       for (String ppName : postProcessorNames) {
    6.           if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
    7.               BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
    8.               priorityOrderedPostProcessors.add(pp);
    9.               if (pp instanceof MergedBeanDefinitionPostProcessor) {
    10.                   internalPostProcessors.add(pp);
    11.               }
    12.           } else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
    13.               orderedPostProcessorNames.add(ppName);
    14.           } else {
    15.               nonOrderedPostProcessorNames.add(ppName);
    16.           }
    17.       }

    阶段4-对各个分组排序后注册备用

    ```java // First, register the BeanPostProcessors that implement PriorityOrdered. sortPostProcessors(priorityOrderedPostProcessors, beanFactory); registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

// Next, register the BeanPostProcessors that implement Ordered. List orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size()); 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. List nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size()); 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. 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). beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext)); ```