运行结果如下：这些bean 都是可以直接用的。
Let's inspect the beans provided by Spring Boot:

application

beanNameHandlerMapping

defaultServletHandlerMapping

dispatcherServlet

embeddedServletContainerCustomizerBeanPostProcessor

handlerExceptionResolver

httpRequestHandlerAdapter

messageSource

mvcContentNegotiationManager

mvcConversionService

mvcValidator

org.springframework.boot.autoconfigure.MessageSourceAutoConfiguration

org.springframework.boot.autoconfigure.PropertyPlaceholderAutoConfiguration

org.springframework.boot.autoconfigure.web.EmbeddedServletContainerAutoConfiguration

org.springframework.boot.autoconfigure.web.EmbeddedServletContainerAutoConfiguration$DispatcherServletConfiguration

org.springframework.boot.autoconfigure.web.EmbeddedServletContainerAutoConfiguration$EmbeddedTomcat

org.springframework.boot.autoconfigure.web.ServerPropertiesAutoConfiguration

org.springframework.boot.context.embedded.properties.ServerProperties

org.springframework.context.annotation.ConfigurationClassPostProcessor.enhancedConfigurationProcessor

org.springframework.context.annotation.ConfigurationClassPostProcessor.importAwareProcessor

org.springframework.context.annotation.internalAutowiredAnnotationProcessor

org.springframework.context.annotation.internalCommonAnnotationProcessor

org.springframework.context.annotation.internalConfigurationAnnotationProcessor

org.springframework.context.annotation.internalRequiredAnnotationProcessor

org.springframework.web.servlet.config.annotation.DelegatingWebMvcConfiguration

propertySourcesBinder

propertySourcesPlaceholderConfigurer

requestMappingHandlerAdapter

requestMappingHandlerMapping

resourceHandlerMapping

simpleControllerHandlerAdapter

tomcatEmbeddedServletContainerFactory

viewControllerHandlerMapping

eg code:

@Bean

  public CommandLineRunner commandLineRunner(ApplicationContext ctx){

return args -> {

String[] names =ctx.getBeanDefinitionNames();

Arrays.sort(names);

for(String s:names){

System.out.println(s);

}

};

}