Qt parsing json using network response binary

Question

Alright, I found something I just don't understand. I am making a request to a web service using QtNetworkManager. For some reason I can't seem to go from the network response to a jsondoc directly, I have to cast it into a string and then BACK into uft8?

void WebAPIengine::handleNetworkData(QNetworkReply *networkReply)
{

//No network error
if (!networkReply->error()){

    //Cast to string
    QString strReply = (QString)networkReply->readAll();

    //This works, jsonDoc will have the json response from webpage
    QJsonDocument jsonDoc = QJsonDocument::fromJson(strReply.toUtf8());

    //This doesn't work, networkReply->readAll() is said to return a QByteArray. 
    QJsonDocument jsonDoc2 = QJsonDocument::fromBinaryData(networkReply->readAll());
    QJsonObject jsonObj = jsonDoc.object();
    data = jsonObj;
}
//Network error
else{
    data["Error"] = "WebAPIengine::handleNetworkData()";
}

Now I can not understand why jsonDoc is working and jsonDoc2 is not. Can someone explain?

Nithish · Accepted Answer · 2014-10-18 07:21:13Z

2

Once you do a QNetworkReply->readAll(), the QNetworkReply object will be empty. So if you call the QNetworkReply->readAll() method again, you will not get anything.

Moreover I don't understand why you are converting the QByteArray returned by QNetworkReply->readAll() into a QString and then converting it back to QByteArray(by calling QString::toUtf8()) to give it to the QJsonDocument::fromJson function.

You can try doing this:

QByteArray temp = newReply->readAll();
QJsonDocument  jsonDoc = QJsonDocument::fromJson(temp); // This should work

Also make sure to know what the content of the JSon document is, i.e. if it is a map (QJsonObject), array(QJSonArray), array of maps or map with an array as value.

edited Oct 18, 2014 at 7:21

answered Oct 18, 2014 at 6:19

Nithish

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5 Comments

Dave851 Over a year ago

alright, looks like I've a mistake in reading my debugger. That was working all along it looks like I'm not pulling out the information correctly. Going to edit post quiet a bit.

Dave851 Over a year ago

And nevermind, just ran all the json["xx"].isXXX() and managed to figure out how to read the data back in.

Nithish Over a year ago

Ok. Good to know that you fixed it.

Dave851 Over a year ago

Yea, didn't relize that QJsonObjects could nest. Was trying to read it as an array and was coming up empty every time

Nithish Over a year ago

You can do something like: if(jsonDoc.object().find("XYZ").value().isArray()) { } else { }

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