protected ConfigurableApplicationContext createApplicationContext(){
        Class<?> contextClass=this.applicationContextClass;
        if(contextClass==null){
        //根据当前应用类型加载基本Context环境
        try{
        switch(this.webApplicationType){
        case SERVLET:
        //我们是传统的Servlet应用,这里通过SPI加载了org.springframework.boot."
        //"web.servlet.context路劲下的AnnotationConfigServletWebServerApplicationContext类  
        contextClass=Class.forName(DEFAULT_SERVLET_WEB_CONTEXT_CLASS);
        break;
//······删除了......

@Override
public void refresh()throws BeansException,IllegalStateException{
synchronized (this.startupShutdownMonitor){
        //准备上下文环境
        prepareRefresh();
        //建立beanFactory,加载了bean的定义,进行resources(xml,properties......)解析
        ConfigurableListableBeanFactory beanFactory=obtainFreshBeanFactory();
        //为beanFactory进行了各种填充
        prepareBeanFactory(beanFactory);
        try{
        //为beanFactory添加后置处理器,并且对Web应用程序(session......)
        //的各种生命域进行了注册,允许context子类对beanFactory进行后处理
        postProcessBeanFactory(beanFactory);
        //在context中注册、调用了beanFactory的后置处理器,并且对@Configration,@Bean......注解进行了处理,这里主要对bean的定义信息的配置
        invokeBeanFactoryPostProcessors(beanFactory);
        //注册实例化bean的拦截器
        registerBeanPostProcessors(beanFactory);
        //初始化ConfigurableListableBeanFactory的MessageSources
        initMessageSource();
        //初始化ApplicationEventMulticaster
        initApplicationEventMulticaster();
        // 初始化Tomcat容器,并且启动
        onRefresh();
        //listeners的注册,以及广播的发布
        registerListeners();
        // 初始化非惰性单例bean
        finishBeanFactoryInitialization(beanFactory);
        // Last step: publish corresponding event.
        finishRefresh();
        }
        catch(BeansException ex){
        // 清理已经创建的单例资源
        destroyBeans();
        // 重置激活状态
        cancelRefresh(ex);
        // Propagate exception to caller.
        throw ex;
        }
        finally{
        //重置Spring的常见反射元数据缓存
        resetCommonCaches();
        }
        }
        }

• 初始化应用环境environment的Context以及Config
• 对listeners,event初始化
    protected void prepareRefresh(){
        // 激活容器.
        this.startupDate=System.currentTimeMillis();
        this.closed.set(false);
        this.active.set(true);
        if(logger.isDebugEnabled()){
        if(logger.isTraceEnabled()){
        logger.trace("Refreshing "+this);
        }
        else{
        logger.debug("Refreshing "+getDisplayName());
        }
        }
        //采用实际实例替换掉environment的Context以及Config,为当前无法操作,但是以后存在操作的预留的占位符
        initPropertySources();
        //验证Environment指定的属性不能为空
        getEnvironment().validateRequiredProperties();
        //为所有liteners初始化
        if(this.earlyApplicationListeners==null){
        this.earlyApplicationListeners=new LinkedHashSet<>(this.applicationListeners);
        }
        else{
        //重置所有Listeners
        this.applicationListeners.clear();
        this.applicationListeners.addAll(this.earlyApplicationListeners);
        }
        //初始化事件,保证广播一经创建,则发布所有事件
        this.earlyApplicationEvents=new LinkedHashSet<>();
        }

• obtainFreshBeanFactory代码体
• 建立了BeanFactory,并且对xml文件进行了读取,解释
    protected ConfigurableListableBeanFactory obtainFreshBeanFactory(){
        //看后面
        refreshBeanFactory();
        return getBeanFactory();
        }

protected final void refreshBeanFactory()throws BeansException{
        //当前是否存在bean工厂
        if(hasBeanFactory()){
        //如果存在则销毁这个工厂存在的所有单例bean
        destroyBeans();
        //然后初始化bean的id,置当前context的BeanFactory为空
        closeBeanFactory();
        }
        try{
        //默认创建DefaultListableBeanFactory工厂,并将此上下文父级的内部 bean工厂作为父bean工厂
        DefaultListableBeanFactory beanFactory=createBeanFactory();
        //为beanFactory设置序列化id
        beanFactory.setSerializationId(getId());
        //自定义beanFactory设置,是否允许覆盖同一key的bean;是否允许循环引用
        customizeBeanFactory(beanFactory);
        //加载定义bean的详细信息
        loadBeanDefinitions(beanFactory);
        this.beanFactory=beanFactory;
        }
        catch(IOException ex){
        throw new ApplicationContextException("I/O error parsing bean definition source for "+getDisplayName(),ex);
        }
        }

protected DefaultListableBeanFactory createBeanFactory(){
        //默认此context创建一个DefaultListableBeanFactory.
        return new DefaultListableBeanFactory(getInternalParentBeanFactory());
        };
protected BeanFactory getInternalParentBeanFactory(){
        //如果实现了ConfigurableApplicationContext,则返回父上下文的内部bean工厂;否则,返回父上下文本身.
        return(getParent()instanceof ConfigurableApplicationContext?
        ((ConfigurableApplicationContext)getParent()).getBeanFactory():getParent());
        }

//bean定义阅读器的规范接口,但是不需要强制实现
public interface BeanDefinitionReader {
  /**
   * 返回bean工厂以注册bean定义.
   * 工厂通过BeanDefinitionRegistry接口暴露,
   * 封装了与bean定义处理相关的方法
   */
  BeanDefinitionRegistry getRegistry();
  /**
   * 获取资源加载器,以用于加载bean资源
   */
  @Nullable
  ResourceLoader getResourceLoader();
  /**
   * 获取bean的classLoader
   */
  @Nullable
  ClassLoader getBeanClassLoader();
  /**
   * 获取bean名字规范定义的加载器
   */
  BeanNameGenerator getBeanNameGenerator();
  /**
   * 从指定Resource加载bean的定义.
   */
  int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException;
  /**
   * 从多个Resource加载bean的定义.
   */
  int loadBeanDefinitions(Resource... resources) throws BeanDefinitionStoreException;
  /**
   * 从指定位置资源加载bean的定义
   */
  int loadBeanDefinitions(String location) throws BeanDefinitionStoreException;
  /**
   * 从多个指定位置资源加载bean的定义
   */
  int loadBeanDefinitions(String... locations) throws BeanDefinitionStoreException;
}

protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory){
        //添加后置处理器,并且转化为bean
        beanFactory.addBeanPostProcessor(new WebApplicationContextServletContextAwareProcessor(this));
        //忽略ServletContextAware.class接口的自动装配
        beanFactory.ignoreDependencyInterface(ServletContextAware.class);
        //BeanFactory注册web应用特有的局部作用域
        registerWebApplicationScopes();
        }

private void registerWebApplicationScopes(){
        //构建request,session作用域,默认为null
        ExistingWebApplicationScopes existingScopes=new ExistingWebApplicationScopes(getBeanFactory());
        //初始化request= new RequestScope() ,session=new SessionScope(),并且刷新scope
        WebApplicationContextUtils.registerWebApplicationScopes(getBeanFactory());
        //为BeanFactory注册局部作用域(scope)
        existingScopes.restore();
        }