Spring Boot系列--启动方法prepareContext

参考版本：2.0.8.RELEASE

启动方法run中prepareContext方法的执行

/**
 * Run the Spring application, creating and refreshing a new
 * {@link ApplicationContext}.
 * @param args the application arguments (usually passed from a Java main method)
 * @return a running {@link ApplicationContext}
 */
public ConfigurableApplicationContext run(String... args) {
   StopWatch stopWatch = new StopWatch();
   stopWatch.start();
   ConfigurableApplicationContext context = null;
   Collection exceptionReporters = new ArrayList<>();
   configureHeadlessProperty();
//启动Spring应用运行监听器
   SpringApplicationRunListeners listeners = getRunListeners(args);
   listeners.starting();
   try {
      ApplicationArguments applicationArguments = new DefaultApplicationArguments(
            args);
//配置环境
      ConfigurableEnvironment environment = prepareEnvironment(listeners,
            applicationArguments);
      configureIgnoreBeanInfo(environment);
//打印banner
      Banner printedBanner = printBanner(environment);
//创建ApplicationContext，并确定类型
      context = createApplicationContext();
//加载异常报告器类并实例化
      exceptionReporters = getSpringFactoriesInstances(
            SpringBootExceptionReporter.class,
            new Class[] { ConfigurableApplicationContext.class }, context);
//Spring上下文前置处理
      prepareContext(context, environment, listeners, applicationArguments,
            printedBanner);
      refreshContext(context);
      afterRefresh(context, applicationArguments);
      stopWatch.stop();
      if (this.logStartupInfo) {
         new StartupInfoLogger(this.mainApplicationClass)
               .logStarted(getApplicationLog(), stopWatch);
      }
      listeners.started(context);
      callRunners(context, applicationArguments);
   }
   catch (Throwable ex) {
      handleRunFailure(context, ex, exceptionReporters, listeners);
      throw new IllegalStateException(ex);
   }

   try {
      listeners.running(context);
   }
   catch (Throwable ex) {
      handleRunFailure(context, ex, exceptionReporters, null);
      throw new IllegalStateException(ex);
   }
   return context;
}

private void prepareContext(ConfigurableApplicationContext context,
      ConfigurableEnvironment environment, SpringApplicationRunListeners listeners,
      ApplicationArguments applicationArguments, Banner printedBanner) {
   context.setEnvironment(environment);
   postProcessApplicationContext(context);
//应用上下文的初始化器，执行一些初始化操作
   applyInitializers(context);
//
   listeners.contextPrepared(context);
   if (this.logStartupInfo) {
//打印启动日志信息
      logStartupInfo(context.getParent() == null);
      logStartupProfileInfo(context);
   }

   // Add boot specific singleton beans注册两个特殊的单例
   context.getBeanFactory().registerSingleton("springApplicationArguments",
         applicationArguments);
   if (printedBanner != null) {
      context.getBeanFactory().registerSingleton("springBootBanner", printedBanner);
   }

   // Load the sources
   Set