使用QNetworkAccessManager发布请求

Question

i use QNetworkAccessManager post request to a website:

    void Spider::getProducts()
    {
        connect(&manager, SIGNAL(finished(QNetworkReply*)), this, SLOT(getProducts(QNetworkReply*)));

        request.setHeader(QNetworkRequest::ContentTypeHeader, "application/x-www-form-urlencoded");

        request.setUrl(QUrl("http://www.example.com/query"));

        for(int i = 0; i < categories.size(); ++i)
        {
            if(categories[i].isCategory())
            {
                isSubCategory = false;

                emit manager.finished(reply);
            }
            else
            {
                for(int page_number = 0; page_number < categories[i].getPageCount(); ++i)
                {
                    isSubCategory = true;

                    QJsonObject json;

                    json.insert("NValue", categories[i].getNValue());
                    json.insert("NodeId", categories[i].getNodeId());
                    json.insert("StoreId", categories[i].getStoreId());
                    json.insert("StoreType", categories[i].getStoreType());
                    json.insert("PageNumber", ++page_number);
                    json.insert("SubCategoryId", categories[i].getSubCategoryId());

                    QJsonDocument doc;

                    doc.setObject(json);

                    QByteArray request_body = doc.toJson();

                    manager.post(request, request_body);
                }
            }
        }
    }

when i run this program, at beginning, this program run normally, after running for a while, it will stop: neither terminated nor continue to run. i can not figure out why it behavior like this? is there anything that needed to be noticed when use QNetworkAccess ? or i am refused by that website? ...

Answer 1

You are using the same QNetworkAccessManager object in a loop multiple times. It is incorrect. For each separate post request you need a separate QNetworkAccessManager object if you want to send requests in parallel. Else if you only want to use a single instance then you need to serialize your post requests by sending next post request when the previous ends in the finished slot.

Updated: Try out this code, it uses single QNetworkAccessManager object, you will need to check for correct place of i++ as per your needs

connect(&manager, SIGNAL(finished(QNetworkReply*)),
this, SLOT(getProducts(QNetworkReply*))); // add this to constructor of your program

void Spider::getProducts()
    {
        static int i = 0;
        request.setHeader(QNetworkRequest::ContentTypeHeader, "application/x-www-form-urlencoded");

        request.setUrl(QUrl("http://www.example.com/query"));

        while(categories[i].isCategory())
        {
            isSubCategory = false;
            i++;
        }
        if(i == categories.size())
        {
           emit allPostRequestsDone();
           return;
        }

            else
            {
                i++;
                if(page_number < categories[i].getPageCount())
                {
                    isSubCategory = true;

                    QJsonObject json;

                    json.insert("NValue", categories[i].getNValue());
                    json.insert("NodeId", categories[i].getNodeId());
                    json.insert("StoreId", categories[i].getStoreId());
                    json.insert("StoreType", categories[i].getStoreType());
                    json.insert("PageNumber", ++page_number);
                    json.insert("SubCategoryId", categories[i].getSubCategoryId());

                    QJsonDocument doc;

                    doc.setObject(json);

                    QByteArray request_body = doc.toJson();

                    manager.post(request, request_body);
                }
            }
        }
    }