@RequestMapping("/login")
 @ResponseBody
 public Object login(@Valid LoginForm form, BindingResult result) {
   System.out.println(result.getFieldError().getDefaultMessage());
   Object[] objects = result.getFieldError().getArguments();
   System.out.println("objects[0]=" + objects[0]);
   Message.Builder builder = Message.newBuilder();
   return builder.build();
 }