code: public String save() {
      Long userId = getLong("user.id");
      if (ValidEntityKeyPredicate.Instance.apply(userId)) {
        User user = userService.get(userId);
        User manager = userService.get(SecurityUtils.getUsername());
        if (userService.isManagedBy(manager, user)) {
          return updateAccount(userId);
        } else {
          return null;
        }
      } else {
        addError("error.parameters.needed");
        return ERROR;
      }
    }
docs: 更新其他用户帐户