Spring IOC源码分析-invokeBeanFactoryPostProcessors（三）

JasonExplorer
539 阅读2分钟

这是我参与8月更文挑战的第25天，活动详情查看：8月更文挑战

前言

写着写着发现是Spring源码劝退系列了, 但是Spring源码的内容确实太多了, 还是从refresh模板方法里核心方法说起. invokeBeanFactoryPostProcessors方法会实例化和调用所有 BeanFactoryPostProcessor（包括其子类 BeanDefinitionRegistryPostProcessor）.

BeanFactoryPostProcessor 接口是 Spring 初始化 BeanFactory 时对外暴露的扩展点，Spring IoC 容器允许 BeanFactoryPostProcessor 在容器实例化任何 bean 之前读取 bean 的定义，并可以修改它.(这个也是Spring生态如此火爆的原因, 提供了一系列的扩展点,方便第三方的框架去集成).

BeanDefinitionRegistryPostProcessor 继承自 BeanFactoryPostProcessor，比 BeanFactoryPostProcessor 具有更高的优先级，主要用来在常规的 BeanFactoryPostProcessor 检测开始之前注册其他 bean 定义。

Spring 源码分析系列

源码分析

1. refresh#invokeBeanFactoryPostProcessors

protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
   // 1. getBeanFactoryPostProcessors() 获取当前应用上下文
   // 2. invokeBeanFactoryPostProcessors 实例化并调用所有已注册的BeanFactoryPostProcessors
   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()));
   }
}

2. getBeanFactoryPostProcessors

// 获取上下文已经注册的beanFactoryPostProcessors
// 在默认情况下，this.beanFactoryPostProcessors 是返回空的。
public List<BeanFactoryPostProcessor> getBeanFactoryPostProcessors() {
   return this.beanFactoryPostProcessors;
}

getBeanFactoryPostProcessors() 会拿到当前应用上下文中已经注册的 BeanFactoryPostProcessor，在默认情况下，this.beanFactoryPostProcessors 是返回空的。

那么如何添加一个BeanFactoryPostProcessor到beanFactory 中呢?

两种方法

  1. 注解的方式，将自己实现的beanFactoryPostProcessor注册到beanFactory中.
  2. 新建一个 ApplicationContextInitializer 的实现类 SpringApplicationContextInitializer ，并在 initialize 方法中写我们的逻辑.
// 注解的方式, 实现BeanFactoryPostProcessor
@Component
public class MyBeanPostProcessor implements BeanFactoryPostProcessor {
   @Override
   public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
      System.out.println("this is my BeanFactoryPostProcessor");
   }
}


// 不需要component注解
public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
   @Override
   public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
      System.out.println("this is my BeanFactoryPostProcessor2");
   }
}

// 通过ApplicationContextInitializer实现类添加BeanFactoryPostProcessor
public class SpringApplicationContextInitializer implements ApplicationContextInitializer<ConfigurableApplicationContext> {
   @Override
   public void initialize(ConfigurableApplicationContext applicationContext) {
      MyBeanFactoryPostProcessor myBeanFactoryPostProcessor = new MyBeanFactoryPostProcessor();
      applicationContext.addBeanFactoryPostProcessor(myBeanFactoryPostProcessor);
   }
}

3. invokeBeanFactoryPostProcessors

public static void invokeBeanFactoryPostProcessors(
      ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {

   // Invoke BeanDefinitionRegistryPostProcessors first, if any.
   Set<String> processedBeans = new HashSet<>();

   // 1. 判断beanFactory 是否是 BeanDefinitionRegistry
   if (beanFactory instanceof BeanDefinitionRegistry) {
      BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
      // 用于存放普通的 BeanFactoryPostProcessor
      List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
      // 用于存放 BeanDefinitionRegistryPostProcessor
      // mybatis 就是用BeanDefinitionRegistryPostProcessor后置处理器来实现bean和beandefinition的
      List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();

      // 2. 遍历所有的beanFactoryPostProcessors, 将普通的BeanFactoryPostProcessor 和 BeanDefinitionRegistryPostProcessor 分别处理
      for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
         if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
            BeanDefinitionRegistryPostProcessor registryProcessor =
                  (BeanDefinitionRegistryPostProcessor) postProcessor;
            registryProcessor.postProcessBeanDefinitionRegistry(registry);
            registryProcessors.add(registryProcessor);
         }
         else {
            regularPostProcessors.add(postProcessor);
         }
      }

      // 保存本次要执行的 BeanDefinitionRegistryPostProcessor
      List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();

      // First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
      // 3. 调用所有实现PriorityOrdered接口的BeanDefinitionRegistryPostProcessors实现类
      // 3.1 找出BeanDefinitionRegistryPostProcessor 接口Bean的BeanName
      String[] postProcessorNames =
            beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
      // 3.2 遍历 postProcessorNames
      for (String ppName : postProcessorNames) {
         // 3.3 校验是否实现了 PriorityOrdered 接口
         if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
            // 3.4 获取 ppName 对应的Bean实例, 添加到currentRegistryProcessors 中
            currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
            // 3.5 防重
            processedBeans.add(ppName);
         }
      }
      // 3.6 排序(根据是否实现了 PriorityOrdered, Ordered接口和order值来排序)
      sortPostProcessors(currentRegistryProcessors, beanFactory);
      // 3.7 添加到 registryProcessors
      registryProcessors.addAll(currentRegistryProcessors);
      // 3.8 遍历currentRegistryProcessors 并执行BeanDefinitionRegistryPostProcessor
      invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
      // 3.9 清空
      currentRegistryProcessors.clear();

      // Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
      // 4. 调用实现了Ordered接口的BeanDefinitionRegistryPostProcessor实现类
      // 4.1 找出所有实现BeanDefinitionRegistryPostProcessor接口的类
      postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
      for (String ppName : postProcessorNames) {
         // 校验是否实现了 Ordered 接口
         if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
            currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
            processedBeans.add(ppName);
         }
      }
      sortPostProcessors(currentRegistryProcessors, beanFactory);
      registryProcessors.addAll(currentRegistryProcessors);
      // 4.2 遍历currentRegistryProcessors并执行BeanDefinitionRegistryPostProcessor
      invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
      currentRegistryProcessors.clear();

      // Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
      // 5. 最后,调用所有剩下的 BeanDefinitionRegistryPostProcessors
      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;
            }
         }
         sortPostProcessors(currentRegistryProcessors, beanFactory);
         registryProcessors.addAll(currentRegistryProcessors);
         invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
         currentRegistryProcessors.clear();
      }

      // Now, invoke the postProcessBeanFactory callback of all processors handled so far.
      // 6. 调用所有 BeanDefinitionRegistryPostProcessor 的 postProcessBeanFactory 方法
      invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
      // 7. 最后调用入参普通 regularPostProcessors的 postProcessBeanFactory 方法
      invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
   }

   else {
      // Invoke factory processors registered with the context instance.
      invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
   }

   // Do not initialize FactoryBeans here: We need to leave all regular beans
   // uninitialized to let the bean factory post-processors apply to them!
   // 开始处理容器中的 BeanFactoryPostProcessor, 流程其实和上面类似
   // 8. 找出BeanFactoryPostProcessor 接口的实现类
   String[] postProcessorNames =
         beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

   // Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
   // Ordered, and the rest.
   List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
   List<String> orderedPostProcessorNames = new ArrayList<>();
   List<String> nonOrderedPostProcessorNames = new ArrayList<>();
   for (String ppName : postProcessorNames) {
      if (processedBeans.contains(ppName)) {
         // skip - already processed in first phase above
      }
      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);
      }
   }

   // First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
   sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
   invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

   // Next, invoke the BeanFactoryPostProcessors that implement Ordered.
   List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
   for (String postProcessorName : orderedPostProcessorNames) {
      orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
   }
   sortPostProcessors(orderedPostProcessors, beanFactory);
   invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);

   // Finally, invoke all other BeanFactoryPostProcessors.
   List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
   for (String postProcessorName : nonOrderedPostProcessorNames) {
      nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
   }
   invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);

   // Clear cached merged bean definitions since the post-processors might have
   // modified the original metadata, e.g. replacing placeholders in values...
   beanFactory.clearMetadataCache();
}
avatar
文章
阅读
粉丝