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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

 关于初始化器的解释可参见，回头再自己整理

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