Xpressengine\User\UserHandler::validateDisplayName PHP Method

    public function validateDisplayName($name)
    {
        if ($name === null || empty($name)) {
            $e = new InvalidArgumentException();
            $e->setMessage('회원이름은 공백이 될 수 없습니다.');
            throw $e;
        }
        $validate = $this->validator->make(['name' => $name], ['name' => ['display_name']]);
        if ($validate->fails()) {
            $e = new InvalidArgumentException();
            $e->setMessage('회원이름 형식이 잘못되었습니다.');
            throw $e;
        }
        if ($this->users()->where(['displayName' => $name])->first() !== null) {
            throw new DisplayNameAlreadyExistsException();
        }
        return true;
    }

 public function update($userId, Request $request)
 {
     // basic validation
     $this->validate($request, ['displayName' => 'required']);
     // member validation
     /** @var UserInterface $user */
     $user = $this->handler->users()->find($userId);
     if ($user === null) {
         throw new UserNotFoundException();
     }
     $displayName = $request->get('displayName');
     $introduction = $request->get('introduction');
     // displayName validation
     if ($user->getDisplayName() !== trim($displayName)) {
         $this->handler->validateDisplayName($displayName);
     }
     XeDB::beginTransaction();
     try {
         // resolve profile file
         if ($profileFile = $request->file('profileImgFile')) {
             /** @var UserImageHandler $imageHandler */
             $imageHandler = app('xe.user.image');
             $user->profileImageId = $imageHandler->updateUserProfileImage($user, $profileFile);
         }
         $this->handler->update($user, compact('displayName', 'introduction'));
     } catch (\Exception $e) {
         XeDB::rollback();
         throw $e;
     }
     XeDB::commit();
     return redirect()->route('member.profile', [$user->getId()])->with('alert', ['type' => 'success', 'message' => '변경되었습니다.']);
 }