springboot之ApplicationContextInitializer都干了些什么

初始化方法

org.springframework.boot.context.config.DelegatingApplicationContextInitializer

	@Override
	public void initialize(ConfigurableApplicationContext context) {
		ConfigurableEnvironment environment = context.getEnvironment();
		/**
		* 初始化环境变量中的context.initializer.classes指定的类
		**/
		List<Class<?>> initializerClasses = getInitializerClasses(environment);
		if (!initializerClasses.isEmpty()) {
			applyInitializerClasses(context, initializerClasses);
		}
	}

也就是说没有定义的话，就不会初始化了。

org.springframework.boot.autoconfigure.SharedMetadataReaderFactoryContextInitializer

	@Override
	public void initialize(ConfigurableApplicationContext applicationContext) {
		/**
		* 注册一个元数据读取的工厂类
		**/
		applicationContext.addBeanFactoryPostProcessor(new CachingMetadataReaderFactoryPostProcessor());
	}

org.springframework.boot.context.ContextIdApplicationContextInitializer

	@Override
	public void initialize(ConfigurableApplicationContext applicationContext) {
		ContextId contextId = getContextId(applicationContext);
		applicationContext.setId(contextId.getId());
		/**
		* 注册一个ContextId对象
		**/
		applicationContext.getBeanFactory().registerSingleton(ContextId.class.getName(), contextId);
	}

org.springframework.boot.context.ConfigurationWarningsApplicationContextInitializer

	@Override
	public void initialize(ConfigurableApplicationContext context) {
		/**
		* 注入ComponentScan检查处理对象
		**/
		context.addBeanFactoryPostProcessor(new ConfigurationWarningsPostProcessor(getChecks()));
	}

org.springframework.boot.rsocket.context.RSocketPortInfoApplicationContextInitializer

	@Override
	public void initialize(ConfigurableApplicationContext applicationContext) {
			/**
		* 注入一个端口检查和设置的监听器，对应的事件RSocketServerInitializedEvent
		**/
		applicationContext.addApplicationListener(new Listener(applicationContext));
	}

org.springframework.boot.web.context.ServerPortInfoApplicationContextInitializer

	@Override
	public void initialize(ConfigurableApplicationContext applicationContext) {
		/**
			注册了一个监听org.springframework.boot.web.context.WebServerInitializedEvent事件的监听器，用于设置端口信息
		**/
		applicationContext.addApplicationListener(this);
	}

org.springframework.boot.autoconfigure.logging.ConditionEvaluationReportLoggingListener

	@Override
	public void initialize(ConfigurableApplicationContext applicationContext) {
		this.applicationContext = applicationContext;
		applicationContext.addApplicationListener(new ConditionEvaluationReportListener());
		if (applicationContext instanceof GenericApplicationContext) {
			// Get the report early in case the context fails to load
			// 注册一个监听ApplicationEvent事件的监听器用于打印自动配置后的日志信息
			this.report = ConditionEvaluationReport.get(this.applicationContext.getBeanFactory());
		}
	}

所有的这些初始化类都没偶进行启动服务的实质性操作，都是通过注册对象，埋点，后面invokeBeanFactoryPostProcessors才真正调用初始化方法，而且在项目启动之前