private TubeMQResult handleQueryCanWriteRequest(String req) {
        QueryCanWriteReq queryCanWriteReq = gson.fromJson(req, QueryCanWriteReq.class);
        if (!queryCanWriteReq.legal()) {
            return TubeMQResult.errorResult(TubeMQErrorConst.PARAM_ILLEGAL);
        }
        return topicService.queryCanWrite(queryCanWriteReq.getTopicName(), queryCanWriteReq.getClusterId());
    }
Handles 'QUERY_CAN_WRITE' method request.

@param req The JSON request
@return TubeMQResult based on the request
inlong-tubemq/tubemq-manager/src/main/java/org/apache/inlong/tubemq/manager/controller/topic/TopicWebController.java