How can I get data from Wikipedia?

haifisch

I have a class for parsing pages:
loader.h

#ifndef LOADER_H
#define LOADER_H

#include <QObject>
#include <QNetworkAccessManager>
#include <QNetworkReply>

class Loader : public QObject
{
    Q_OBJECT
public:
    explicit Loader(QObject *parent = nullptr);
    void makeRequest(QString endPointRequest);
signals:
    void dataReadyRead(QByteArray);
public slots:
    void ReadRead(QNetworkReply *reply);
private:
    QNetworkAccessManager *m_manager= new QNetworkAccessManager(this);
};

#endif // LOADER_H

loader.cpp

#include "loader.h"

Loader::Loader(QObject *parent) : QObject(parent)
{
    connect(m_manager,SIGNAL(finished(QNetworkReply*)),this,SLOT(ReadRead(QNetworkReply*)));
}

void Loader::makeRequest(QString endPointRequest)
{
    m_manager->get(QNetworkRequest(QUrl(endPointRequest)));
}

void Loader::ReadRead(QNetworkReply *reply)
{
    QByteArray myData;
    myData = reply->readAll();
    emit dataReadyRead(myData);
}

And in the basic form I pass the reference for parsing :

MainWindow::MainWindow(QWidget *parent) :
        QMainWindow(parent),
        ui(new Ui::MainWindow)
    {
        ui->setupUi(this);
        connect(&theLoader,SIGNAL(dataReadyRead(QByteArray)),this,SLOT(dataUploaded(QByteArray)) );
    }
    ...
    void MainWindow::on_pushButton_4_clicked()
    {
        theLoader.makeRequest("http://ru.wikipedia.org/w/api.php?action=query&format=json&titles=Ключевая%20ставка%20в%20России");
    }
    
    void MainWindow::dataUploaded(QByteArray data)
    {
        QString dataString;
        dataString = data;
        ui->apiResponseDisplay->setText(dataString);
        qDebug()<<dataString;
    }

This code returns a blank page: "".
How can I get data from Wikipedia?

VRonin

Looks like you are just not handling unicode correcly. could you try with an ascii only process and see if that works, you can use https://en.wikipedia.org/w/api.php?action=query&format=json&titles=lemon

Also, make sure you have OpenSSL correctly set up as this is an https request.

You can connect to http://doc.qt.io/qt-5/qnetworkreply.html#sslErrors and http://doc.qt.io/qt-5/qnetworkreply.html#error-1 to detect what's going wrong

haifisch

@VRonin I always get empty results from Wikipedia. Can you write an example, output errors? I do not understand how to use the methods you referred to.

haifisch

@VRonin if(reply->error()) {
qDebug() << "Error!";
qDebug() << reply->errorString();
}
Does not return an error.

VRonin

Try this minimal example:

#include <QCoreApplication>
#include <QNetworkAccessManager>
#include <QNetworkReply>
#include <QNetworkRequest>
#include <QDebug>
#include <QTextStream>
#include <QSslError>

int main(int argc, char *argv[])
{
    QCoreApplication application(argc, argv);
    QNetworkAccessManager qnam;
    const QNetworkRequest wikireq(QUrl(QStringLiteral("https://en.wikipedia.org/w/api.php?action=query&format=json&titles=lemon")));
    QNetworkReply* wikirep = qnam.get(wikireq);
    QObject::connect(wikirep,&QNetworkReply::finished,[wikirep]()->void{
        QTextStream repStream(wikirep);
        qDebug() << "Response Received:\n" << repStream.readAll();
        wikirep->deleteLater();
    });
    QObject::connect(wikirep,QOverload<QNetworkReply::NetworkError>::of(&QNetworkReply::error),[wikirep]()->void{
        qDebug() << "Network Error:\n" << wikirep->errorString();
        wikirep->deleteLater();
    });
    QObject::connect(wikirep,&QNetworkReply::sslErrors,[wikirep](const QList<QSslError> &errors)->void{
        qDebug() << "SSL Errors:";
        for(auto&& err : errors)
            qDebug() << err.errorString();
        wikirep->deleteLater();
    });
    return application.exec();
}

haifisch

@VRonin nothing returns""

haifisch

@VRonin even no error

haifisch

@VRonin behold:
qt.network.ssl: QSslSocket: cannot call unresolved function SSLv23_client_method
qt.network.ssl: QSslSocket: cannot call unresolved function SSL_CTX_new
qt.network.ssl: QSslSocket: cannot call unresolved function SSL_library_init
qt.network.ssl: QSslSocket: cannot call unresolved function ERR_get_error
qt.network.ssl: QSslSocket: cannot call unresolved function ERR_get_error
Network Error:
"Error creating SSL context ()"
Response Received:
""

Taz742

@haifisch
What platform are you using?
For windows you need dll files check this

https://stackoverflow.com/questions/30621577/force-qt5-to-load-ssl-dlls-from-exe-dir
https://forum.qt.io/topic/17139/solved-how-to-use-ssl-support-without-manualy-building-qt-libraries
https://forum.qt.io/topic/15873/openssl-and-qt-need-help/4

haifisch

@Taz742 On Windows / Thanks. I decided already this problemma.link helped