1、new SpringApplication(primarySources)会执行下面初始化
根据meta-INF/spring.factories 会实例如下初始化
SharedmetadataReaderFactoryContextInitializer
ConfigurationWarningsApplicationContextInitializer
ContextIdApplicationContextInitializer
DelegatingApplicationContextInitializer
RSocketPortInfoApplicationContextInitializer
ServerPortInfoApplicationContextInitializer
ConditionevaluationReportLoggingListener
2、初始化完成后会createApplicationContext（）；
执行上面代码会创建 AnnotationConfigServletWebServerApplicationContext
然后这里会创建5个 beanDefinitionNames，加入到BeanFactory，后面会将启动类来加入到beanfactory，总共是6个beanDefinitionNames
加入@EnableWebSocketMessageBroker 这个注解的配置类，import DelegatingWebSocketMessageBrokerConfiguration extends StompBrokerRelayMessageHandler，里面有一@bean，进行初始化
初始化完成后，refreshContext()–>finishRefresh()启动tcp网络监听;如下源码
下面是启动Debug步骤
