How to respond with HTTP 400 error in a Spring MVC @ResponseBody method returning String?

change your return type to ResponseEntity<>, then you can use below for 400

return new ResponseEntity<>(HttpStatus.BAD_REQUEST);

and for correct request

return new ResponseEntity<>(json,HttpStatus.OK);

UPDATE 1

after spring 4.1 there are helper methods in ResponseEntity could be used as

return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(null);

and

return ResponseEntity.ok(json);

Something like this should work, I'm not sure whether or not there is a simpler way:

@RequestMapping(value = "/matches/{matchId}", produces = "application/json")@ResponseBodypublic String match(@PathVariable String matchId, @RequestBody String body,            HttpServletRequest request, HttpServletResponse response) {    String json = matchService.getMatchJson(matchId);    if (json == null) {        response.setStatus( HttpServletResponse.SC_BAD_REQUEST  );    }    return json;}

Not necessarily the most compact way of doing this, but quite clean IMO

if(json == null) {    throw new BadThingException();}...@ExceptionHandler(BadThingException.class)@ResponseStatus(value = HttpStatus.BAD_REQUEST)public @ResponseBody MyError handleException(BadThingException e) {    return new MyError("That doesnt work");}

Edit you can use @ResponseBody in the exception handler method if using Spring 3.1+, otherwise use a ModelAndView or something.

https://jira.springsource.org/browse/SPR-6902