public ConfigurableApplicationContext run(String... args) {
   StopWatch stopWatch = new StopWatch(); //时间计数器，主要记录任务的运行时间 不用管
   stopWatch.start();
   ConfigurableApplicationContext context = null; //初始化一个可配置应用上下文
   FailureAnalyzers analyzers = null; //失败分析器
   configureHeadlessProperty(); //设置系统 awt的头属性信息
   SpringApplicationRunListeners listeners = getRunListeners(args); //设置多个运行监听器
   listeners.starting();
   try {
      ApplicationArguments applicationArguments = new DefaultApplicationArguments(
            args); //设置应用参数
      ConfigurableEnvironment environment = prepareEnvironment(listeners,
            applicationArguments); //得到创建的环境变量，设置监听器的环境
      Banner printedBanner = printBanner(environment); //设置banner，以及banner的资源加载器
      context = createApplicationContext(); //创建应用上下文，可配置的web应用上下文或者标准的应用上下文
      analyzers = new FailureAnalyzers(context); //设置失败分析器 并且判断是否是beanFactoryAware 如果是 将上下文的beanFactory赋值给它的beanFactory
      prepareContext(context, environment, listeners, applicationArguments,
            printedBanner); //设置上下文的环境 监听器 应用参数，横幅
      refreshContext(context);
      afterRefresh(context, applicationArguments);
      listeners.finished(context, null);
      stopWatch.stop();
      if (this.logStartupInfo) {
         new StartupInfoLogger(this.mainApplicationClass)
               .logStarted(getApplicationLog(), stopWatch);
      }
      return context;
   }
   catch (Throwable ex) {
      handleRunFailure(context, listeners, analyzers, ex);
      throw new IllegalStateException(ex);
   }
}

private void prepareContext(ConfigurableApplicationContext context,
      ConfigurableEnvironment environment, SpringApplicationRunListeners listeners,
      ApplicationArguments applicationArguments, Banner printedBanner) {
   context.setEnvironment(environment);
   postProcessApplicationContext(context);
   applyInitializers(context);
   listeners.contextPrepared(context);
   if (this.logStartupInfo) {
      logStartupInfo(context.getParent() == null);
      logStartupProfileInfo(context);
   }

   // Add boot specific singleton beans
   context.getBeanFactory().registerSingleton("springApplicationArguments",
         applicationArguments);
   if (printedBanner != null) {
      context.getBeanFactory().registerSingleton("springBootBanner", printedBanner);
   }

   // Load the sources
   Set<Object> sources = getSources();
   Assert.notEmpty(sources, "Sources must not be empty");
load(context, sources.toArray(new Object[sources.size()]));
   listeners.contextLoaded(context);
}

/**
 * Load beans into the application context.
 * @param context the context to load beans into
 * @param sources the sources to load
 */
protected void load(ApplicationContext context, Object[] sources) {
   if (logger.isDebugEnabled()) {
logger.debug(
            "Loading source " + StringUtils.arrayToCommaDelimitedString(sources));
   }
   BeanDefinitionLoader loader = createBeanDefinitionLoader(
         getBeanDefinitionRegistry(context), sources);
   if (this.beanNameGenerator != null) {
      loader.setBeanNameGenerator(this.beanNameGenerator);
   }
   if (this.resourceLoader != null) {
      loader.setResourceLoader(this.resourceLoader);
   }
   if (this.environment != null) {
      loader.setEnvironment(this.environment);
   }
   loader.load();
}

protected void postProcessApplicationContext(ConfigurableApplicationContext context) {
if (this.beanNameGenerator != null) {
      context.getBeanFactory().registerSingleton(
            AnnotationConfigUtils.CONFIGURATION_BEAN_NAME_GENERATOR,
            this.beanNameGenerator);
   }
if (this.resourceLoader != null) {
if (context instanceof GenericApplicationContext) {
         ((GenericApplicationContext) context)
               .setResourceLoader(this.resourceLoader);
      }
if (context instanceof DefaultResourceLoader) {
         ((DefaultResourceLoader) context)
               .setClassLoader(this.resourceLoader.getClassLoader());
      }
   }
}

private void refreshContext(ConfigurableApplicationContext context) {
   refresh(context);
   if (this.registerShutdownHook) {
      try {
         context.registerShutdownHook();
      }
      catch (AccessControlException ex) {
         // Not allowed in some environments.
      }
   }
}