SpringBoot启动源码解读（2）

如果是web环境，那么context是 AnnotationConfigEmbeddedWebApplicationContext 类的实例。该类的构造方法如下：

public AnnotationConfigEmbeddedWebApplicationContext() {
    this.reader = new AnnotatedBeanDefinitionReader(this);
    this.scanner = new ClassPathBeanDefinitionScanner(this);
}

// 创建函数如下
public AnnotatedBeanDefinitionReader(BeanDefinitionRegistry registry, Environment environment) {

   Assert.notNull(registry, "BeanDefinitionRegistry must not be null");
   Assert.notNull(environment, "Environment must not be null");
   this.registry = registry;
   this.conditionEvaluator =new ConditionEvaluator(registry, environment, null);
   //  创建注解配置处理器
   AnnotationConfigUtils.registerAnnotationConfigProcessors(this.registry);
}

public static SetregisterAnnotationConfigProcessors(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 beanDefs =new LinkedHashSet(4);
// 注册ConfigurationClassPostProcessor这个beanFactoryProceesor。该类的目的是处理@Configuration注解的
   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));
   }

// 注册AutowiredAnnotationBeanPostProcessor这个beanPostProccesor，该类的目的是处理@Autowired注解
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));
   }

// 注册 RequiredAnnotationBeanPostProcessor， 该beanPostProccessor主要是处理@Required注解
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));
   }

// 注册CommonAnnotationBeanPostProcessor，处理包括@PostConstruct，@PreDestroy注解
// Check for JSR-250 support, and if present add the CommonAnnotationBeanPostProcessor.
   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;
}