把你的返回类型改成ResponseEntity，然后你就可以用下面的400

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

return new ResponseEntity<>(HttpStatus.BAD_REQUEST);

为了正确的请求

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

更新 1

在 spring 4.1 之后，ResponseEntity 中的辅助方法可以用作

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

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

和

return ResponseEntity.ok(json);