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<BeanFactoryPostProcessor> beanFactoryPostProcessors = new ArrayList<>();

public List<BeanFactoryPostProcessor> 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<BeanFactoryPostProcessor> beanFactoryPostProcessors) {

   Set<String> processedBeans = new HashSet<>();

   // 对 BeanDefinitionRegistry 类型的处理

   if (beanFactory instanceof BeanDefinitionRegistry) {

      BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;

      List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();

      List<BeanDefinitionRegistryPostProcessor> 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<BeanDefinitionRegistryPostProcessor> 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<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();

   List<String> orderedPostProcessorNames = new ArrayList<>();

   List<String> 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<BeanFactoryPostProcessor> 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<BeanFactoryPostProcessor> 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<Object> comparatorToUse = null;

   if (beanFactory instanceof DefaultListableBeanFactory) {

      comparatorToUse = ((DefaultListableBeanFactory) beanFactory).getDependencyComparator();

   }

   if (comparatorToUse == null) {

      comparatorToUse = OrderComparator.INSTANCE;

   }

   postProcessors.sort(comparatorToUse);

}

2-1 调用 Bean 定义注册表增强器

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


private static void invokeBeanDefinitionRegistryPostProcessors( Collection<? extends BeanDefinitionRegistryPostProcessor> 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<String> 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();

}

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