看下面一段代码，为什么一个@SpringBootApplication注解，就能够自动的执行N多的工作呢？

@EnableAsync
@SpringBootApplication
public class NimitzApplication {

    public static void main(String[] args) {
        new SpringApplicationBuilder(NimitzApplication.class).web(true).run(args);
    }
}

过程

• 1 SpringApplication.run(Object source, String... args) 

• 2 核心过程在ConfigurableApplicationContext run(String... args)

ApplicationArguments applicationArguments = new DefaultApplicationArguments(
                    args);
            ConfigurableEnvironment environment = prepareEnvironment(listeners,
                    applicationArguments);
            Banner printedBanner = printBanner(environment);
            context = createApplicationContext();
            analyzers = new FailureAnalyzers(context);
            prepareContext(context, environment, listeners, applicationArguments,
                    printedBanner);
            refreshContext(context);
            afterRefresh(context, applicationArguments);
            listeners.finished(context, null);
            stopWatch.stop();
            if (this.logStartupInfo) {
                new StartupInfoLogger(this.mainApplicationClass)
                        .logStarted(getApplicationLog(), stopWatch);
            }
            

• 3 魔法过程 

SpringApplication.refreshContext 
->  AbstractApplicationContext.invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) 
-> PostProcessorRegistrationDelegate.invokeBeanDefinitionRegistryPostProcessors
-> ConfigurationClassPostProcessor.processConfigBeanDefinitions 
-> ConfigurationClassParser.parse 
-> ConfigurationClassParser.processConfigurationClass

// 最终 sourceClass是所有魔法的入口了
-> ConfigurationClassParser.doProcessConfigurationClass(configClass, sourceClass);

 5 @import是最核心的注解,各种功能实际上是由三种类型的实现的
 @Configuration classes, ImportSelector and ImportBeanDefinitionRegistrar implementations