模块装配@EnableWebMvc

```

@Retention(RetentionPolicy.RUNTIME)

@Target(ElementType.TYPE)

@Documented

@Import(DelegatingWebMvcConfiguration.class)

public @interface EnableWebMvc {}

```

DelegatingWebMvcConfiguration继承WebMvcConfigurationSupport

WebMvcConfigurationSupport初始化了很多bean

例如：RequestMappingHandlerMapping 

/**

* Return a {@link RequestMappingHandlerMapping} ordered at 0 for mapping

* requests to annotated controllers.

*/

@Bean

public RequestMappingHandlerMapping requestMappingHandlerMapping() {

RequestMappingHandlerMapping mapping = createRequestMappingHandlerMapping();

。。。

return mapping;

}