Spring源码之四prepareBeanFactory()方法

//bean初始化方法调用前被调用
    @Nullable
    default Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        return bean;
    }
    
    //bean初始化方法调用后被调用
    @Nullable
    default Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        return bean;
    }

    // Tell the internal bean factory to use the context's class loader etc.
        //设置上下文环境的启动类加载器
        beanFactory.setBeanClassLoader(getClassLoader());

        //添加bean表达式解释器，为了能够让我们的beanFactory去解析bean表达式
        beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));

        //spring内部的属性编辑器、既读取配置文件
        beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));

        // Configure the bean factory with context callbacks.
        //添加BeanPostProcessor
        beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));

        //跳过以下6个属性的自动注入
        //因为在ApplicationContextAwareProcessor后置处理器中通过setter注入
        beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
        beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
        beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
        beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
        beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
        beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);

        // BeanFactory interface not registered as resolvable type in a plain factory.
        // MessageSource registered (and found for autowiring) as a bean.

        ////注册四个特殊的bean
        //在应用代码就可以通过类型自动装配把工厂实例和ApplicationContext实例设置到自定义bean的属性中
        //这四个属性都会被自动设置，虽然没有在显示的在bean定义xml中注入它们
        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.
        //注册事件监听器
        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()));
        }

        // Register default environment beans.
        // 如果没有定义 "environment" 这个 bean，那么 Spring 会 "手动" 注册一个
        if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) {
            beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
        }
        // 如果没有定义 "systemProperties" 这个 bean，那么 Spring 会 "手动" 注册一个
        if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) {
            beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());
        }
        // 如果没有定义 "systemEnvironment" 这个 bean，那么 Spring 会 "手动" 注册一个
        if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) {
            beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());
        }