问为什么@ComponentScan对不同的配置文件有不同的行为？

EN

@Configuration
@EnableWebMvc
@ComponentScan(basePackages = {"org.zerock.controller"}) // This Works.
public class ServletConfig implements WebMvcConfigurer {
    @Bean
    public MultipartResolver multipartResolver(){
        return new StandardServletMultipartResolver();
    }

    @Override
    public void configureViewResolvers(ViewResolverRegistry registry) {
        InternalResourceViewResolver resolver = new InternalResourceViewResolver();
        resolver.setPrefix("/WEB-INF/views/");
        resolver.setSuffix(".jsp");
        registry.viewResolver(resolver);
    }


    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        registry.addResourceHandler("/resources/**").addResourceLocations("/resources/");
    }
}

@Configuration
//@ComponentScan(basePackages = {"org.zerock.controller"}) This Doesn't Work
public class RootConfig {
}

// How the two configuration classes are initialized
public class WebConfig extends AbstractAnnotationConfigDispatcherServletInitializer {
    @Override
    protected Class<?>[] getRootConfigClasses() {
        return new Class[]{RootConfig.class};
    }

    @Override
    protected Class<?>[] getServletConfigClasses() {
        return new Class[]{ServletConfig.class};
    }