查看springboot在启动的时候为我们注入了哪些bean

在程序入口加入：

@SpringBootApplication
public class SpringbootFirstApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringbootFirstApplication.class, args);
    }

    @Bean
    public CommandLineRunner commandLineRunner(ApplicationContext ctx) {
        return args -> {

            System.out.println("Let's inspect the beans provided by Spring Boot:");

            String[] beanNames = ctx.getBeanDefinitionNames();
            Arrays.sort(beanNames);
            for (String beanName : beanNames) {
                System.out.println(beanName);
            }

        };
    }

}

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程序输出：

Let’s inspect the beans provided by Spring Boot: 
basicErrorController 
beanNameHandlerMapping 
beanNameViewResolver 
characterEncodingFilter 
commandLineRunner 
conventionErrorViewResolver 
defaultServletHandlerMapping 
defaultViewResolver 
dispatcherServlet 
dispatcherServletRegistration 
duplicateServerPropertiesDetector 
embeddedServletContainerCustomizerBeanPostProcessor 
error 
errorAttributes 
errorPageCustomizer 
errorPageRegistrarBeanPostProcessor

…. 
….

在程序启动的时候，springboot自动诸如注入了40-50个bean.