@Override
 public int hashCode() {
   int result = notifier != null ? notifier.hashCode() : 0;
   result = 31 * result + (server != null ? server.hashCode() : 0);
   result = 31 * result + (details != null ? details.hashCode() : 0);
   result = 31 * result + (request != null ? request.hashCode() : 0);
   result = 31 * result + (error != null ? error.hashCode() : 0);
   return result;
 }