About SpringMVC JAVA ANNOTATION

@EnableWebMvc

Reference

The above registers a RequestMappingHandlerMapping, a RequestMappingHandlerAdapter, and anExceptionHandlerExceptionResolver (among others) in support of processing requests with annotated controller methods using annotations such as @RequestMapping, @ExceptionHandler, and others.

It also enables the following:

1. Spring 3 style type conversion through a ConversionService instance in addition to the JavaBeans PropertyEditors used for Data Binding.
2. Support for formatting Number fields using the @NumberFormat annotation through theConversionService.
3. Support for formatting Date, Calendar, Long, and Joda Time fields using the @DateTimeFormatannotation.
4. Support for validating @Controller inputs with @Valid, if a JSR-303 Provider is present on the classpath.

5. HttpMessageConverter support for @RequestBody method parameters and @ResponseBody method return values from @RequestMapping or @ExceptionHandler methods.

   This is the complete list of HttpMessageConverters set up by mvc:annotation-driven:

   1. ByteArrayHttpMessageConverter converts byte arrays.
   2. StringHttpMessageConverter converts strings.
   3. ResourceHttpMessageConverter converts to/from org.springframework.core.io.Resource for all media types.
   4. SourceHttpMessageConverter converts to/from a javax.xml.transform.Source.
   5. FormHttpMessageConverter converts form data to/from a MultiValueMap<String, String>.
   6. Jaxb2RootElementHttpMessageConverter converts Java objects to/from XML — added if JAXB2 is present on the classpath.
   7. MappingJackson2HttpMessageConverter (or MappingJacksonHttpMessageConverter) converts to/from JSON — added if Jackson 2 (or Jackson) is present on the classpath.
   8. AtomFeedHttpMessageConverter converts Atom feeds — added if Rome is present on the classpath.
   9. RssChannelHttpMessageConverter converts RSS feeds — added if Rome is present on the classpath.

   DOC

   Add this annotation to an @Configuration class to have the Spring MVC configuration defined in WebMvcConfigurationSupport imported:

    @Configuration
    @EnableWebMvc
    @ComponentScan(basePackageClasses = { MyConfiguration.class })
    public class MyWebConfiguration {
    }
   

    

   Customize the imported configuration by implementing the WebMvcConfigurer interface or more likely by extending theWebMvcConfigurerAdapter base class and overriding individual methods:

    

    @Configuration
    @EnableWebMvc
    @ComponentScan(basePackageClasses = { MyConfiguration.class })
    public class MyConfiguration extends WebMvcConfigurerAdapter {
   
           @Override
           public void addFormatters(FormatterRegistry formatterRegistry) {
                   formatterRegistry.addConverter(new MyConverter());
           }
   
           @Override
           public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
                   converters.add(new MyHttpMessageConverter());
           }
   
           // More overridden methods ...
    }
    

    

   If the customization options of WebMvcConfigurer do not expose something you need to configure, consider removing the @EnableWebMvcannotation and extending directly from WebMvcConfigurationSupport overriding selected @Bean methods:

    

    @Configuration
    @ComponentScan(basePackageClasses = { MyConfiguration.class })
    public class MyConfiguration extends WebMvcConfigurationSupport {
   
           @Override
           public void addFormatters(FormatterRegistry formatterRegistry) {
                   formatterRegistry.addConverter(new MyConverter());
           }
   
           @Bean
           public RequestMappingHandlerAdapter requestMappingHandlerAdapter() {
                   // Create or delegate to "super" to create and
                   // customize properties of RequestMapingHandlerAdapter
           }
    }

    

org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport

This is the main class providing the configuration behind the MVC Java config. It is typically imported by adding @EnableWebMvc to an application @Configuration class. An alternative more advanced option is to extend directly from this class and override methods as necessary remembering to add @Configuration to the subclass and @Bean to overridden @Bean methods. For more details see the Javadoc of@EnableWebMvc.

This class registers the following HandlerMappings:

• RequestMappingHandlerMapping ordered at 0 for mapping requests to annotated controller methods.
• HandlerMapping ordered at 1 to map URL paths directly to view names.
• BeanNameUrlHandlerMapping ordered at 2 to map URL paths to controller bean names.
• HandlerMapping ordered at Integer.MAX_VALUE-1 to serve static resource requests.
• HandlerMapping ordered at Integer.MAX_VALUE to forward requests to the default servlet.

Registers these HandlerAdapters:

• RequestMappingHandlerAdapter for processing requests with annotated controller methods.
• HttpRequestHandlerAdapter for processing requests with HttpRequestHandlers.
• SimpleControllerHandlerAdapter for processing requests with interface-based Controllers.

Registers a HandlerExceptionResolverComposite with this chain of exception resolvers:

• ExceptionHandlerExceptionResolver for handling exceptions through @ExceptionHandler methods.
• ResponseStatusExceptionResolver for exceptions annotated with @ResponseStatus.
• DefaultHandlerExceptionResolver for resolving known Spring exception types

Both the RequestMappingHandlerAdapter and the ExceptionHandlerExceptionResolver are configured with default instances of the following by default:

• A ContentNegotiationManager
• A DefaultFormattingConversionService
• A LocalValidatorFactoryBean if a JSR-303 implementation is available on the classpath
• A range of HttpMessageConverters depending on the 3rd party libraries available on the classpath.

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

A sub-class of WebMvcConfigurationSupport that detects and delegates to all beans of type WebMvcConfigurer allowing them to customize the configuration provided by WebMvcConfigurationSupport. This is the class actually imported by @EnableWebMvc.

 org.springframework.web.servlet.config.annotation.WebMvcConfigurer

Defines callback methods to customize the Java-based configuration for Spring MVC enabled via @EnableWebMvc.

@EnableWebMvc-annotated configuration classes may implement this interface to be called back and given a chance to customize the default configuration. Consider extending WebMvcConfigurerAdapter, which provides a stub implementation of all interface methods.

org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter

 An implementation of WebMvcConfigurer with empty methods allowing sub-classes to override only the methods they're interested in.

 搞清这四个类的关系。