synchronized (this.startupShutdownMonitor) {// 准备刷新上下文环境prepareRefresh();// 初始化BeanFactory，并进行XML文件的读取 之前大部分IOC的核心逻辑都在这里ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();//对BeanFactory进行各种功能填充prepareBeanFactory(beanFactory);try {// 留给子类进行服务覆盖和扩展的方法.postProcessBeanFactory(beanFactory);//激活各种BeanFactory处理器.invokeBeanFactoryPostProcessors(beanFactory);//激活Bean后处理器，在getBean时候调用，而BeanFactory后处理器是容器级别的，在此时就会被调用.registerBeanPostProcessors(beanFactory);//资源国际化处理.initMessageSource();// 初始化广播器，用于放所有的bean的监听器，并放入BeanFactory属性applicationEventMulticaster中.initApplicationEventMulticaster();// 留给子类去初始化其他bean，目前方法为空.onRefresh();// 查找bean的所有的监听器，并注册到广播器中去.registerListeners();// 初始化剩下的单实例.finishBeanFactoryInitialization(beanFactory);// 完成刷新过程，通知生命周期.finishRefresh();}

protected void prepareRefresh() {//留给子类覆盖的方法
        initPropertySources();// Validate that all properties marked as required are resolvable// 验证所需的属性已经存放到环境中
        getEnvironment().validateRequiredProperties();// Allow for the collection of early ApplicationEvents,// to be published once the multicaster is available...this.earlyApplicationEvents = new LinkedHashSet<ApplicationEvent>();}

public class MyClassPathXmlApplicationContext extends ClassPathXmlApplicationContext{public MyClassPathXmlApplicationContext(String... configLocations) throws BeansException {super(configLocations);}protected void initPropertySources(){// 在这里设置需要检测的环境变量 VARgetEnvironment().setRequiredProperties("VAR");}protected void customizeBeanFactory(DefaultListableBeanFactory beanFactory){super.setAllowCircularReferences(false);super.setAllowBeanDefinitionOverriding(false);super.customizeBeanFactory(beanFactory);}
}