@RequestBody

• HttpRequest body를 domain object로 전송.

  • 이때 자동으로 HttpRequest body를 Java Object 형태로 deserialize해준다.

  @PostMapping("/request")
  public ResponseEntity postController(
    @RequestBody LoginForm loginForm) {
   
      exampleService.fakeAuthenticate(loginForm);
      return ResponseEntity.ok(HttpStatus.OK);
  }
  

  • 여기서 Spring은 JSON을 JavaType으로 deserialize해줌(적절한 것이 명세되었을 것이라고 가정하고)
  • 기본적으로 @RequestBody annotation과 우리가 annotate한 type은 반드시 JSON 형식과 일치해야한다!

@ResponseBody

• 반환하는 object는 자동으로 JSON type으로 serialize 되어야 하고, HttpResponse object로 돌려주어야 한다고 controller에 말해주는 역할이다.

  @Controller
  @RequestMapping("/post")
  public class ExamplePostController {
  
      @Autowired
      ExampleService exampleService;
  
      @PostMapping("/response")
      @ResponseBody
      public ResponseTransfer postResponseController(
        @RequestBody LoginForm loginForm) {
          return new ResponseTransfer("Thanks For Posting!!!");
       }
  }
  

  • 이렇게 짜서 해주면 반환값은

    {"text":"Thanks For Posting!!!"}
    

    이 response body로 날아온다.

Content type 설정

• @ResponseBody 를 사용할때도 명시적으로 content type을 method return 값에 정의할 수 있다.

  • @PostMapping , @GetMapping 등등 attribute 설정시켜서 해줌.

  @PostMapping(value = "/content", produces = MediaType.APPLICATION_JSON_VALUE)
  @ResponseBody
  public ResponseTransfer postResponseJsonContent(
    @RequestBody LoginForm loginForm) {
      return new ResponseTransfer("JSON Content!");
  }
  

  • response

    curl -i \\ 
    -H "Accept: application/json" \\ 
    -H "Content-Type:application/json" \\ 
    -X POST --data 
      '{"username": "johnny", "password": "password"}' "<https://localhost:8080/.../content>"
    

조금 더 자세히

• @RequestBody 나 @ResponseBody 를 사용하게 되면, HttpMessageConverter 를 사용해서 객체를 변환시킨다.

  //정의되어있는 default HttpMessageConverter들.
  ByteArrayHttpMessageConverter – converts byte arrays
  StringHttpMessageConverter – converts Strings
  ResourceHttpMessageConverter – converts org.springframework.core.io.Resource for any type of octet stream
  SourceHttpMessageConverter – converts javax.xml.transform.Source
  FormHttpMessageConverter – converts form data to/from a MultiValueMap<String, String>.
  Jaxb2RootElementHttpMessageConverter – converts Java objects to/from XML (added only if JAXB2 is present on the classpath)
  MappingJackson2HttpMessageConverter – converts JSON (added only if Jackson 2 is present on the classpath)
  MappingJacksonHttpMessageConverter – converts JSON (added only if Jackson is present on the classpath)
  AtomFeedHttpMessageConverter – converts Atom feeds (added only if Rome is present on the classpath)
  RssChannelHttpMessageConverter – converts RSS feeds (added only if Rome is present on the classpath)
  

• HttpMessageConverter interface

  public interface HttpMessageConverter<T> {
  
  	/**
  	 * Indicates whether the given class can be read by this converter.
  	 * @param clazz the class to test for readability
  	 * @param mediaType the media type to read (can be {@code null} if not specified);
  	 * typically the value of a {@code Content-Type} header.
  	 * @return {@code true} if readable; {@code false} otherwise
  	 */
  	boolean canRead(Class<?> clazz, @Nullable MediaType mediaType);
  
  	/**
  	 * Indicates whether the given class can be written by this converter.
  	 * @param clazz the class to test for writability
  	 * @param mediaType the media type to write (can be {@code null} if not specified);
  	 * typically the value of an {@code Accept} header.
  	 * @return {@code true} if writable; {@code false} otherwise
  	 */
  	boolean canWrite(Class<?> clazz, @Nullable MediaType mediaType);
  
  	/**
  	 * Return the list of media types supported by this converter. The list may
  	 * not apply to every possible target element type and calls to this method
  	 * should typically be guarded via {@link #canWrite(Class, MediaType)
  	 * canWrite(clazz, null}. The list may also exclude MIME types supported
  	 * only for a specific class. Alternatively, use
  	 * {@link #getSupportedMediaTypes(Class)} for a more precise list.
  	 * @return the list of supported media types
  	 */
  	List<MediaType> getSupportedMediaTypes();
  
  	/**
  	 * Return the list of media types supported by this converter for the given
  	 * class. The list may differ from {@link #getSupportedMediaTypes()} if the
  	 * converter does not support the given Class or if it supports it only for
  	 * a subset of media types.
  	 * @param clazz the type of class to check
  	 * @return the list of media types supported for the given class
  	 * @since 5.3.4
  	 */
  	default List<MediaType> getSupportedMediaTypes(Class<?> clazz) {
  		return (canRead(clazz, null) || canWrite(clazz, null) ?
  				getSupportedMediaTypes() : Collections.emptyList());
  	}
  
  	/**
  	 * Read an object of the given type from the given input message, and returns it.
  	 * @param clazz the type of object to return. This type must have previously been passed to the
  	 * {@link #canRead canRead} method of this interface, which must have returned {@code true}.
  	 * @param inputMessage the HTTP input message to read from
  	 * @return the converted object
  	 * @throws IOException in case of I/O errors
  	 * @throws HttpMessageNotReadableException in case of conversion errors
  	 */
  	T read(Class<? extends T> clazz, HttpInputMessage inputMessage)
  			throws IOException, HttpMessageNotReadableException;
  
  	/**
  	 * Write an given object to the given output message.
  	 * @param t the object to write to the output message. The type of this object must have previously been
  	 * passed to the {@link #canWrite canWrite} method of this interface, which must have returned {@code true}.
  	 * @param contentType the content type to use when writing. May be {@code null} to indicate that the
  	 * default content type of the converter must be used. If not {@code null}, this media type must have
  	 * previously been passed to the {@link #canWrite canWrite} method of this interface, which must have
  	 * returned {@code true}.
  	 * @param outputMessage the message to write to
  	 * @throws IOException in case of I/O errors
  	 * @throws HttpMessageNotWritableException in case of conversion errors
  	 */
  	void write(T t, @Nullable MediaType contentType, HttpOutputMessage outputMessage)
  			throws IOException, HttpMessageNotWritableException;
  
  }
  

• 이거 이제 맞춰서 변환된다.

참고