public function getConfigValue() {
    $session = $this->getSession();
    $request = $this->getRequest();
    $response = $this->getResponse();

    // load model
    $value = null;
    $authUser = $this->principalFactory->getUser($session->getAuthUser());
    if ($authUser) {
      $configKey = $request->getValue('name');

      // find configuration
      $configObj = null;
      $configList = Node::filter($authUser->getValue('UserConfig'), null, null,
              ['name' => $configKey]);
      $value = sizeof($configList) > 0 ?
              $configObj = $configList[0]->getValue('value') : null;
    }
    $response->setValue('value', $value);

    // success
    $response->setAction('ok');
  }