深入理解 Spring BeanFactoryPostProcessor的回调（一）

public AnnotationConfigApplicationContext(Class<?>... annotatedClasses) {
  this();
  register(annotatedClasses)
  refresh();
}

public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
  // Prepare this context for refreshing.
  //准备刷新
  prepareRefresh();
    //获取BeanFactory 
  ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
    // 准备BeanFactory
  prepareBeanFactory(beanFactory);
  try {
    // 方法中没有任何实现的逻辑
    postProcessBeanFactory(beanFactory);
    // invoke BeanFactoryPostprocessor, 执行bean工厂的后置处理器
    //如果我们没有手动往Spring中注入bean工厂的后置处理器,那么此时仅有一个,也是beanFactoryMap中的第一个RootBeanDefinition-> ConfigurationClassPostProcessor
    invokeBeanFactoryPostProcessors(beanFactory);
    // 注册 bean的后置处理器, 这些处理器可以在bean的构造方法执行之后再执行init()方法前后执行指定的逻辑
    registerBeanPostProcessors(beanFactory);
    // Initialize message source for this context.
    initMessageSource();
    // Initialize event multicaster for this context.
    initApplicationEventMulticaster();
    // Initialize other special beans in specific context subclasses.
    onRefresh();
    // Check for listener beans and register them.
    registerListeners();
    // Instantiate all remaining (non-lazy-init) singletons.
    finishBeanFactoryInitialization(beanFactory);
    // Last step: publish corresponding event.
    finishRefresh();
  }
  }
}

protected void prepareRefresh() {
    this.startupDate = System.currentTimeMillis();
    this.closed.set(false);
    this.active.set(true);
    if (logger.isInfoEnabled()) {
      logger.info("Refreshing " + this);
    }
    //  这个是protected类型的方法,目前还没有任何实现
    initPropertySources();
    //   校验所有需要的properties是否都被解析过了
    //   getEnvironment() 得到系统环境, 后续的@Profile使用
    getEnvironment().validateRequiredProperties();
    this.earlyApplicationEvents = new LinkedHashSet<>();
  }

@Override
  public abstract ConfigurableListableBeanFactory getBeanFactory() throws IllegalStateException;

protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
  // 添加类加载器
  beanFactory.setBeanClassLoader(getClassLoader());
  // 设置bean标签的解析器, 一般我们使用spel标签比较多,但是Spring也有自己的Bean标签 
  beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
  // </property ref="XXX"> 解析转换xxx 替换成对象
  beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));
  // 添加bean的后置处理器,很显然这里添加的是Spring自己的后置处理器
  beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
  // 当用户企图注入下面类型的对象时, 会被Spring忽略
  beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
  beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
  beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
  beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
  beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
  beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);
  //用户穿进来的是 BeanFactory.class , 那Spring会将她替换成beanFactory
  beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
  beanFactory.registerResolvableDependency(ResourceLoader.class, this);
  beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
  beanFactory.registerResolvableDependency(ApplicationContext.class, this);
  // Register early post-processor for detecting inner beans as ApplicationListeners.
  beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));
  // Detect a LoadTimeWeaver and prepare for weaving, if found.
  if (beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
    beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
    // Set a temporary ClassLoader for type matching.
    beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
  }
  // 意思是如果自定义的Bean中没有名为"systemProperties"和"systemEnvironment"的Bean，
  // 则注册两个Bena，Key为"systemProperties"和"systemEnvironment"，Value为Map，
  // 这两个Bean就是一些系统配置和系统环境信息
  //  注册默认的和环境相关的 bean   Sping会检测,我们自己注册进来的Bean中有没有下面的名字叫下面三个串的对象, 没有的话就帮我们注入进来
  if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) { //   environment_bean_name
    beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
  }
  if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) {//   system_properties_bean_name
    beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());
  }
  if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) {//   system_environment_bean_name
    beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());
  }
}