c++ - Qt http bad request on google -

i'm trying create url shortener app using google's url shortener api (https://developers.google.com/url-shortener/v1/getting_started#shorten). problem bad request. here error: error: error downloading https://www.googleapis.com/urlshortener/v1/url - server replied: bad request

what did wrong? here code:

void mainwindow::ppp(qstring longurl) {     qnetworkaccessmanager* manager = new qnetworkaccessmanager(this);     connect(manager, signal(finished(qnetworkreply *)), this, slot(replyfinished(qnetworkreply *)));      qurl url = qurl("https://www.googleapis.com/urlshortener/v1/url");      qnetworkrequest request(url);     request.setheader(request.contenttypeheader,"application/json");      qbytearray postdata;     postdata.append("longurl");     postdata.append(longurl);       manager->post(request,postdata); }  void mainwindow::replyfinished(qnetworkreply *reply) {     if(reply->error() != qnetworkreply::noerror)     {         ui->textbrowser->settext("error: " +  reply->errorstring());     }     else     {         qbytearray responsedata = reply->readall();         qstring qstr(responsedata);         ui->textbrowser->settext(qstr);     } } 

you have send post data in json format.

to make code work, replace

qbytearray postdata; postdata.append("longurl"); postdata.append(longurl); 

with this

qbytearray postdata; postdata.append("{\"longurl\": \""+longurl+"\"}");