Spring rest 可以返回自定義http code

參考資料：

http://stackoverflow.com/questions/16232833/how-to-respond-with-http-400-error-in-a-spring-mvc-responsebody-method-returnin#comment23256806_16250729

@RequestMapping(value = "/matches/{matchId}", produces = "application/json")
@ResponseBody
public 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;
}