What is the difference between ResponseEntity<T> and @ResponseBody?

Question

I have a simple handler in my controller which returns a message

@RequestMapping(value = "/message") @ResponseBody public Message get() {     return new Message(penguinCounter.incrementAndGet() + " penguin!"); } 

At the same time I can use something like this

@RequestMapping(value = "/message") ResponseEntity<Message> get() {     Message message = new Message(penguinCounter.incrementAndGet() + " penguin!");     return new ResponseEntity<Message>(message, HttpStatus.OK); } 

What is the difference betweet this two approaches? Let's not take into account HttpStatus :)

Answer 1

ResponseEntity will give you some added flexibility in defining arbitrary HTTP response headers. See the 4th constructor here:

http://docs.spring.io/spring/docs/3.0.x/api/org/springframework/http/ResponseEntity.html

ResponseEntity(T body, MultiValueMap<String,String> headers, HttpStatus statusCode)  

A List of possible HTTP response headers is available here:

http://en.wikipedia.org/wiki/List_of_HTTP_header_fields#Responses

Some commonly-used ones are Status, Content-Type and Cache-Control.

If you don't need that, using @ResponseBody will be a tiny bit more concise.

Answer 2

HttpEntity represents an HTTP request or response consists of headers and body.

// Only talks about body & headers, but doesn't talk about status code public HttpEntity(T body, MultiValueMap<String,String> headers) 

ResponseEntity extends HttpEntity but also adds a Http status code.

// i.e ResponseEntity = HttpEntity + StatusCode public ResponseEntity(T body, MultiValueMap<String,String> headers, HttpStatus statusCode) 

Hence used to fully configure the HTTP response.

For Ex:

@ControllerAdvice  public class JavaWebExeptionHandler {      @Autowired     ExceptionErrorCodeMap exceptionErrorCodeMap;      @ExceptionHandler(RuntimeException.class)     public final ResponseEntity<ExceptionResponseBody> handleAllExceptions(Exception ex) {         Integer expCode = exceptionErrorCodeMap.getExpCode(ex.getClass());         // We have not added headers to response here, If you want you can add by using respective constructor         return new ResponseEntity<ExceptionResponseBody>(new ExceptionResponseBody(expCode, ex.getMessage()),                 HttpStatus.valueOf(expCode));     }  } 

@ResponseBody indicates that return value of method on which it is used is bound to the response body (Mean the return value of method is treated as Http response body)