Spring中提供了一個介面ApplicationContext，用於擴充套件BeanFactory中現有的功能。它提供了更多的功能。現在我們來看下它的實現：

    public ClassPathXmlApplicationContext(String[] configLocations, boolean refresh, ApplicationContext parent)
            throws BeansException {

        super(parent);
        setConfigLocations(configLocations);
        if (refresh) {
            refresh();
        }
    }
 

其中refresh();方法幾乎包含了所有的功能，邏輯非常清晰

public void refresh() throws BeansException, IllegalStateException {
        synchronized (this.startupShutdownMonitor) {
            // Prepare this context for refreshing.
            //環境準備，比如系統屬性、環境變數的初始化及驗證
            prepareRefresh();

            // Tell the subclass to refresh the internal bean factory.
            //初始化BeanFactory
            ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

            // Prepare the bean factory for use in this context.
            //對BeanFactory進行各種功能填充
            prepareBeanFactory(beanFactory);

            try {
                // Allows post-processing of the bean factory in context subclasses.
                //子類覆蓋方法做額外處理
                postProcessBeanFactory(beanFactory);

                // Invoke factory processors registered as beans in the context.
                //啟用各種BeanFactory處理器
                invokeBeanFactoryPostProcessors(beanFactory);

                // Register bean processors that intercept bean creation.
                //註冊攔截Bean建立的Bean處理器，這裡只是註冊，真正地呼叫在getBean的時候，比如配置檔案通過${}讀取等
                registerBeanPostProcessors(beanFactory);

                // Initialize message source for this context.
                //為上下文初始化Message源，（比如國際化處理）
                initMessageSource();

                // Initialize event multicaster for this context.
                //初始化應用訊息廣播，並放入 applicationEventMulticaster bean中
                initApplicationEventMulticaster();

                // Initialize other special beans in specific context subclasses.
                //留給子類來初始化其它的bean
                onRefresh();

                // Check for listener beans and register them.
                //在所有註冊的bean中查詢Listener bean，註冊到訊息廣播器中
                registerListeners();

                // Instantiate all remaining (non-lazy-init) singletons.
                //初始化剩下的單例項
                finishBeanFactoryInitialization(beanFactory);

                //完成重新整理過程，通知生命週期護處理器lifecycleProcessor重新整理過程，同時發出ContextRefreshEvent通知別人（LifecycleProcessor 用來與所有宣告的bean的週期做狀態更新）
                // 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();
            }
        }
    }