Spring MVC中@ResponseBody方法中如何返回HTTP400错误呢?

ResponseBody注解返回http400状态码的方法
   借助ResponseEntity对象返回
    在返回ResponseEntity时传入相应的状态码

注意事项
   此种方法必须将返回类型设置为ResponseEntity类型

 
@RequestMapping(value = "/matches/{matchId}", produces = "application/json")
@ResponseBody
public String match(@PathVariable String matchId) {
    String json = matchService.getMatchJson(matchId);
    if (json == null) {
 
    }
    return json;
}

修改为

@RequestMapping(value = "/matches/{matchId}", produces = "application/json")
@ResponseBody
public ResponseEntity match(@PathVariable String matchId) {
    String json = matchService.getMatchJson(matchId);
    if (json == null) {
 
		return new ResponseEntity<>(HttpStatus.BAD_REQUEST);
		//或
       return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(null);
    }
    return return new ResponseEntity<>(json,HttpStatus.OK);;
}