message: alert export api
diff: /*
  * @Author: liwenjie
  * @Date: 2021-09-23 16:55:53
  - * @LastEditTime: 2022-04-19 10:44:06
  + * @LastEditTime: 2022-04-19 17:24:50
  * @LastEditors: Please set LastEditors
  * @Description: In User Settings Edit
  * @FilePath: /gstore/Main/ghttp.cpp
  @@ -2046,20 +2046,17 @@ void export_thread_new(const shared_ptr<HttpServer::Request>& request, const sha
  }
  db_path = db_path + db_name +"_"+Util::get_timestamp()+ ".nt";
  //check if database named [db_name] is already load
  - if(!apiUtil->check_already_load(db_name))
  + Database *current_database = apiUtil->get_database(db_name);
  + if(current_database == NULL)
  {
  string error = "Database not load yet.";
  sendResponseMsg(1004, error ,operation, request, response);
  return;
  }
  - Database *current_database = apiUtil->get_database(db_name);
  apiUtil->rdlock_database(db_name);//lock database
  -
  - string sparql = "select * where {?x ?y ?z.} ";
  - ResultSet rs;
  - Util::formatPrint("db_path: " + db_path);
  + Util::formatPrint("export_path: " + db_path);
  FILE* ofp = fopen(db_path.c_str(), "w");
  - int ret = current_database->query(sparql, rs, ofp, false, true);
  + current_database->export_db(ofp);
  fflush(ofp);
  fclose(ofp);
  ofp = NULL;
  