protected function checkObjects($objectMap) {
    $response = $this->getResponse();
    $invalidOids = [];
    foreach ($objectMap as $parameterName => $object) {
      if ($object == null) {
        $invalidOids[] = $parameterName;
      }
    }
    if (sizeof($invalidOids) > 0) {
      $response->addError(ApplicationError::get('OID_INVALID',
        ['invalidOids' => $invalidOids]));
      return false;
    }
    return true;
  }