Spring 源码（二）注册内置的BeanPostProcessor的BeanDefinition到容器

发起注册

调用链路：

registerAnnotationConfigProcessors:163, AnnotationConfigUtils (org.springframework.context.annotation)
registerAnnotationConfigProcessors:134, AnnotationConfigUtils (org.springframework.context.annotation)
<init>:83, AnnotatedBeanDefinitionReader (org.springframework.context.annotation)
<init>:66, AnnotatedBeanDefinitionReader (org.springframework.context.annotation)
<init>:61, AnnotationConfigApplicationContext (org.springframework.context.annotation)
<init>:82, AnnotationConfigApplicationContext (org.springframework.context.annotation)      

源码：

// 注册 Spring 内置后置处理器的 BeanDefinition
public static Set<BeanDefinitionHolder> registerAnnotationConfigProcessors(
    BeanDefinitionRegistry registry, Object source) {

  DefaultListableBeanFactory beanFactory = unwrapDefaultListableBeanFactory(registry);
  if (beanFactory != null) {
    if (!(beanFactory.getDependencyComparator() instanceof AnnotationAwareOrderComparator)) {
      beanFactory.setDependencyComparator(AnnotationAwareOrderComparator.INSTANCE);
    }
    if (!(beanFactory.getAutowireCandidateResolver() instanceof ContextAnnotationAutowireCandidateResolver)) {
      beanFactory.setAutowireCandidateResolver(new ContextAnnotationAutowireCandidateResolver());
    }
  }

  Set<BeanDefinitionHolder> beanDefs = new LinkedHashSet<BeanDefinitionHolder>(4);

  if (!registry.containsBeanDefinition(CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)) {
    RootBeanDefinition def = new RootBeanDefinition(ConfigurationClassPostProcessor.class);
    def.setSource(source);
    beanDefs.add(registerPostProcessor(registry, def, CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME));
  }
  // 对注解@Autowired的实现
  if (!registry.containsBeanDefinition(AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME)) {
    RootBeanDefinition def = new RootBeanDefinition(AutowiredAnnotationBeanPostProcessor.class);
    def.setSource(source);
    beanDefs.add(registerPostProcessor(registry, def, AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME));
  }
  // 对注解 @Required 的实现
  if (!registry.containsBeanDefinition(REQUIRED_ANNOTATION_PROCESSOR_BEAN_NAME)) {
    RootBeanDefinition def = new RootBeanDefinition(RequiredAnnotationBeanPostProcessor.class);
    def.setSource(source);
    beanDefs.add(registerPostProcessor(registry, def, REQUIRED_ANNOTATION_PROCESSOR_BEAN_NAME));
  }

  // Check for JSR-250 support, and if present add the CommonAnnotationBeanPostProcessor.
  // 对JSR-250的支持，如对 @Resource、@PostConstruct和@PreDestroy 的实现
  if (jsr250Present && !registry.containsBeanDefinition(COMMON_ANNOTATION_PROCESSOR_BEAN_NAME)) {
    RootBeanDefinition def = new RootBeanDefinition(CommonAnnotationBeanPostProcessor.class);
    def.setSource(source);
    beanDefs.add(registerPostProcessor(registry, def, COMMON_ANNOTATION_PROCESSOR_BEAN_NAME));
  }

  // Check for JPA support, and if present add the PersistenceAnnotationBeanPostProcessor.
  if (jpaPresent && !registry.containsBeanDefinition(PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME)) {
    RootBeanDefinition def = new RootBeanDefinition();
    try {
      def.setBeanClass(ClassUtils.forName(PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME,
          AnnotationConfigUtils.class.getClassLoader()));
    }
    catch (ClassNotFoundException ex) {
      throw new IllegalStateException(
          "Cannot load optional framework class: " + PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME, ex);
    }
    def.setSource(source);
    beanDefs.add(registerPostProcessor(registry, def, PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME));
  }

  if (!registry.containsBeanDefinition(EVENT_LISTENER_PROCESSOR_BEAN_NAME)) {
    RootBeanDefinition def = new RootBeanDefinition(EventListenerMethodProcessor.class);
    def.setSource(source);
    beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_PROCESSOR_BEAN_NAME));
  }
  if (!registry.containsBeanDefinition(EVENT_LISTENER_FACTORY_BEAN_NAME)) {
    RootBeanDefinition def = new RootBeanDefinition(DefaultEventListenerFactory.class);
    def.setSource(source);
    beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_FACTORY_BEAN_NAME));
  }

  return beanDefs;
}      

注册Bean定义到容器

调用链路：

registerBeanDefinition:861, DefaultListableBeanFactory (org.springframework.beans.factory.support)
registerBeanDefinition:315, GenericApplicationContext (org.springframework.context.support)
registerPostProcessor:218, AnnotationConfigUtils (org.springframework.context.annotation)
registerAnnotationConfigProcessors:163, AnnotationConfigUtils (org.springframework.context.annotation)
registerAnnotationConfigProcessors:134, AnnotationConfigUtils (org.springframework.context.annotation)
<init>:83, AnnotatedBeanDefinitionReader (org.springframework.context.annotation)
<init>:66, AnnotatedBeanDefinitionReader (org.springframework.context.annotation)
<init>:61, AnnotationConfigApplicationContext (org.springframework.context.annotation)
<init>:82, AnnotationConfigApplicationContext (org.springframework.context.annotation)      

源码：

//---------------------------------------------------------------------
// Implementation of BeanDefinitionRegistry interface
//---------------------------------------------------------------------
// 将BeanDefinition注册到容器
@Override
public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
    throws BeanDefinitionStoreException {

  ...
  if (hasBeanCreationStarted()) {
    // Cannot modify startup-time collection elements anymore (for stable iteration)
    synchronized (this.beanDefinitionMap) {
      this.beanDefinitionMap.put(beanName, beanDefinition);
      List<String> updatedDefinitions = new ArrayList<String>(this.beanDefinitionNames.size() + 1);
      updatedDefinitions.addAll(this.beanDefinitionNames);
      updatedDefinitions.add(beanName);
      this.beanDefinitionNames = updatedDefinitions;
      if (this.manualSingletonNames.contains(beanName)) {
        Set<String> updatedSingletons = new LinkedHashSet<String>(this.manualSingletonNames);
        updatedSingletons.remove(beanName);
        this.manualSingletonNames = updatedSingletons;
      }
    }
  }
  else {
    // Still in startup registration phase
    this.beanDefinitionMap.put(beanName, beanDefinition);
    this.beanDefinitionNames.add(beanName);
    this.manualSingletonNames.remove(beanName);
  }
  ...
}      

这里需要注意的两个后置处理器分别是：

• AutowiredAnnotationBeanPostProcessor：对注解@Autowired的实现
• CommonAnnotationBeanPostProcessor： 对JSR-250的支持，如对 @Resource、@PostConstruct和@PreDestroy 的实现