[SOLVED] Empty QJsonDocument from file

ningu

Hi,

I'm trying to parse an appSettigns.json file that holds some application settings, but when I set the json document with QJsonDocument::fromJson(file.readAll()) the json document stays empty.

Here's the code:

jsonmanager.cpp
@
#include "jsonmanager.h"

#include <QFile>
#include <QDebug>
#include <QJsonDocument>
#include <QJsonObject>

JsonManager::JsonManager(QWidget *parent)
{
QFile file(":/config/appSettings.json");
if (!file.open(QIODevice::ReadOnly | QIODevice::Text)) {
qDebug() << "Could not open file";
qDebug() << file.errorString();
return;
}

QJsonDocument   jsonDoc;
jsonDoc = QJsonDocument::fromJson(file.readAll());
if (!jsonDoc.isNull()) {
    qDebug() << "Could not read data";
}

QJsonObject jsonObj = jsonDoc.object();
QVariantMap jsonMap = jsonObj.toVariantMap();
qDebug() << jsonMap.size();  // outputs 0
// and so does jsonDoc.array().size();

file.close();

}
@

appSettings.json
@{
"osc_port":57120,
"server": {
"path": "/path/to/executable",
"ip": "127.0.0.1",
"port": 54321
},
"data_path": "/path/to/data/folder",
"frame_rate": 25,
"vertical_sync": true,
"threshold": 64,
"camera": {
"device_id": 0,
"width": 640,
"height": 480,
"rotate_180": false,
"use_uvc": false
},
"background_color": {
"red": 64,
"green": 64,
"blue": 64,
"alpha": 255,
},
"tool_highlight_color": {
"red": 240,
"green": 64,
"blue": 64,
"alpha": 128,
}
}
@

I also checked the array in the QJsonDocument but it's empty, too. Any hints on what I'm doing wrong?

Thanks!

kurt.pattyn

In the background_color object, there is a superfluous comma, as well as in tool_highlight_color. Maybe that is your problem.

ningu

Thanks for the quick answer.

Unfortunately, even though you are right, removing the superfluous comma did not solve the problem. The QDomDocument is still empty.

ningu

I think the error is in the loading of the file.
@qDebug() << file.bytesAvailable();@

outputs 0, although it seems to load fine (no error output).

ningu

If I load the data from the file to QDomDocument object it seems to work fine. I very puzzled.

SGaist

Hi,

Just to be on the safe side, did you properly put your json file in the resources (qrc file) ?

You keep talking about QDomDocument, is it a typo ?

ningu

Yes, the file is properly put in my qrc file.

And yes, sorry, when I said

bq. Unfortunately, even though you are right, removing the superfluous comma did not solve the problem. The QDomDocument is still empty.

I meant the QJsonDocument is still empty.

But later on I tried to load the data into a QDomDocument object just to try and it seems to work fine.
@
QDomDocument *domDocument;
if (!domDocument->setContent(&file)) {
qDebug() << "Could not set DOM";
return;
}

qDebug() << domDocument->toString();@

prints the file contents to the console.

Sorry for the confusion I created with the typo.

SGaist

Ok, then what does

@qDebug() << file.readAll()@

return ?

ningu

It returns
@""@

SGaist

Then it seems that your file is empty

ningu

That's what I thought, but
@qDebug() << QString::fromUtf8(file.readAll())@
returns the file contents.

ningu

Might it be an encoding issue?

ningu

Sorry, that was not completely right:
@QString jsonString = QString::fromUtf8(file.readAll());
qDebug() << jsonString;
@
returns the file contents, while
@qDebug() << QString::fromUtf8(file.readAll())@
returns
@""@

SGaist

Strange, QJsonDocument should handle it...
Did you check what error you got when using fromJson ?

ningu

No, I didn't. How could I do that?

ningu

Ok, I got it. A friend of mine pointed me out that I was looking for the array in the QJsonDocument, and that I should probably be looking for the object, which worked.

The only thing that doesn't work right is that
@QString jsonString = QString::fromUtf8(file.readAll());

QJsonDocument jsonDoc = QJsonDocument::fromJson(jsonString.toUtf8());@
works, but
@QJsonDocument jsonDoc = QJsonDocument::fromJson(file.readAll());@
doesn't.

SGaist

Look at the second parameter of "fromJson":http://qt-project.org/doc/qt-5.0/qtcore/qjsondocument.html#fromJson

From there you can get the error

ningu

It's an 'Illegal value' error. But I get the same error even with an empty file.

SGaist

Could it be your json file encoding that is problematic ?

ningu

That might be it. Is there a way to make sure the file is UTF8? Or set it to UTF8?