spring容器的功能扩展

容器的扩展功能主要实现为：

org.springframework.context.support.AbstractApplicationContext.refresh()

    public void refresh() throws BeansException, IllegalStateException {
        synchronized (this.startupShutdownMonitor) {
            // 准备刷新的上下文环境
            // Prepare this context for refreshing.
            prepareRefresh();
            
            // 初始化BeanFactory，并进行xml文件读取
            // Tell the subclass to refresh the internal bean factory.
            ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

            // 对BeanFactory进行各种功能填充
            // Prepare the bean factory for use in this context.
            prepareBeanFactory(beanFactory);

            try {
                // 子类覆盖方法做额外的处理
                // Allows post-processing of the bean factory in context subclasses.
                postProcessBeanFactory(beanFactory);

                // 激活各种BeanFactory处理器
                // Invoke factory processors registered as beans in the context.
                invokeBeanFactoryPostProcessors(beanFactory);

                // 注册拦截bean创建的bean处理器，这里只是注册，真正的调用时在getBean时候
                // Register bean processors that intercept bean creation.
                registerBeanPostProcessors(beanFactory);

                // 为上下文初始化Message源，即不同语言的消息体，国际化处理
                // Initialize message source for this context.
                initMessageSource();

                // 初始化应用消息广播器，并放入ApplicationEventMulticaster中
                // Initialize event multicaster for this context.
                initApplicationEventMulticaster();

                // 留给子类来初始化其他的bean
                // Initialize other special beans in specific context subclasses.
                onRefresh();

                // 在所有注册的bean中查找listener bean，注册到消息广播器中
                // Check for listener beans and register them.
                registerListeners();

                // 初始化剩下的单实例（非延迟加载的）
                // Instantiate all remaining (non-lazy-init) singletons.
                finishBeanFactoryInitialization(beanFactory);

                // 完成刷新过程，通知生命周期处理器lifecycleProcessor刷新过程，同时发出ContextRefreshEvent通知别人
                // Last step: publish corresponding event.
                finishRefresh();
            }

            catch (BeansException ex) {
                // Destroy already created singletons to avoid dangling resources.
                destroyBeans();

                // Reset 'active' flag.
                cancelRefresh(ex);

                // Propagate exception to caller.
                throw ex;
            }
        }
    }

参考：spring源码深度解析