@Override
    public void refresh() throws BeansException, IllegalStateException {
        synchronized (this.startupShutdownMonitor) {
            // Prepare this context for refreshing.
　　　　　　　// 一些初始化，不重要
            prepareRefresh();

            // Tell the subclass to refresh the internal bean factory.
　　　　　　  // 获取beanFactory, 里面主要是BeanDefinitionMap 和BeanDefinitionName
            ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

            // Prepare the bean factory for use in this context.
            prepareBeanFactory(beanFactory);

            try {
                // Allows post-processing of the bean factory in context subclasses.
                postProcessBeanFactory(beanFactory);
　　　　　　　　　　
                // Invoke factory processors registered as beans in the context.
　　　　　　　　　 // 调用所有BeanFactory后处理器： BeanFactoryPostProcessor，默认是空的，可以自己定义
                invokeBeanFactoryPostProcessors(beanFactory);

                // Register bean processors that intercept bean creation.
                // 注册bean后处理器，只是注册到beanFactory， 初始化方法前会调用所有的BeanPostProcessor，
                // 初始化前后调用postProcessorBeforeInitialization/postProcessorAfterInitialization , aop重点看 
                registerBeanPostProcessors(beanFactory);

                // Initialize message source for this context.
                initMessageSource();

                // Initialize event multicaster for this context.
                initApplicationEventMulticaster();

                // Initialize other special beans in specific context subclasses.
　　　　　　　　　 // 提供模板方法 给子类扩展， 默认是空
                onRefresh();

                // Check for listener beans and register them.
                registerListeners();

                // Instantiate all remaining (non-lazy-init) singletons. 
                finishBeanFactoryInitialization(beanFactory);

                // Last step: publish corresponding event.
                finishRefresh();
            }

            catch (BeansException ex) {
                if (logger.isWarnEnabled()) {
                    logger.warn("Exception encountered during context initialization - " +
                            "cancelling refresh attempt: " + ex);
                }

                // Destroy already created singletons to avoid dangling resources.
                destroyBeans();

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

                // Propagate exception to caller.
                throw ex;
            }

            finally {
                // Reset common introspection caches in Spring‘s core, since we
                // might not ever need metadata for singleton beans anymore...
                resetCommonCaches();
            }
        }
    }