Rest client with Qt 4.5

It’s very easy to call a rest service from qt, even with authentication,
using QtNetwork/QNetworkAccessManager class
http://doc.trolltech.com/4.5/qnetworkaccessmanager.html.

Using the previous rest servlet sample.

    QNetworkAccessManager *manager = new QNetworkAccessManager(this);

    QObject::connect(manager, SIGNAL(finished(QNetworkReply *)),
                              SLOT(slotRequestFinished(QNetworkReply *)));

    QNetworkRequest request;
    request.setUrl(QUrl("http://localhost:8080/restservlet/sample/tommy"));
    request.setRawHeader("Authorization", "Basic " +
                         QByteArray(QString("%1:%2").arg("user").arg("asas").toAscii()).toBase64());
    request.setHeader(QNetworkRequest::ContentTypeHeader, "text/xml");

    QNetworkReply *reply = 0;
    reply = manager->get(request);

    QObject::connect(reply, SIGNAL(downloadProgress(qint64,qint64)),
                            SLOT(slotProgress(qint64,qint64)));

void SampleRestClient::slotRequestFinished(QNetworkReply *reply)
{
    if (reply->error() > 0) {
        qDebug() <errorString();
    }
    else {
        QDomDocument doc;
        QXmlInputSource is;
        is.setData(reply->readAll());
        doc.setContent(is.data());

        QDomNodeList nodes = doc.elementsByTagName("message");

        if (nodes.size() > 0) {
            qDebug() << nodes.at(0).toElement ().text ();
        }
    }
}

• We neet to set the Authorization header for the basic http auth mechanism.
  Just “Basic user:password” user and password encoded with base64.
• We can use QDomDocument to get the xml representation of the rest response.

Here is the complete code sample :

• main.cpp

  
  #include "mainwindow.h"
  
  #include <QtGui/QApplication>
  
  int main(int argc, char *argv[])
  {
      QApplication a(argc, argv);
      MainWindow w;
      w.show();
      return a.exec();
  }
  
  

• mainwindow.h

  
  #ifndef MAINWINDOW_H                                                        
  #define MAINWINDOW_H                                                        
  
  #include <QtGui/QWidget>
  
  class QLabel;
  class QProgressBar;
  class QNetworkAccessManager;
  class QNetworkReply;
  
  class MainWindow : public QWidget
  {
      Q_OBJECT
  public:
      MainWindow(QWidget *parent = 0);
      ~MainWindow();
  
  private slots:
      void slotRequestFinished(QNetworkReply *);
      void slotSetProgress(qint64, qint64);
  
  private:
      QLabel *m_label;
      QProgressBar *m_progress;
  
      QNetworkAccessManager *m_network;
  };
  
  #endif // MAINWINDOW_H
  
  

• mainwindow.cpp

  
  #include "mainwindow.h"                                                       
  
  #include <QDebug>
  #include <QThread>
  #include <QtCore/QUrl>
  #include <QtGui/QLabel>
  #include <QtGui/QProgressBar>
  #include <QtGui/QVBoxLayout>
  #include <QtNetwork/QNetworkAccessManager>
  #include <QtNetwork/QNetworkRequest>
  #include <QtNetwork/QNetworkReply>     
  #include <QtNetwork/QNetworkProxy>
  #include <QtXml/QDomDocument>
  
  static const char *REQUEST_URL = "http://localhost:8080/restservlet/rest/sample/tommy";
  static const char *USER = "user";                                                      
  static const char *PASSWORD = "asas";                                                  
  
  MainWindow::MainWindow(QWidget *parent)
      : QWidget(parent)                  
  {                                      
      QVBoxLayout *layout = new QVBoxLayout(this);
  
      m_label = new QLabel();
      m_progress = new QProgressBar();
      m_progress->setRange(0, 100);   
  
      layout->addWidget(m_label);
      layout->addWidget(m_progress);
      setLayout(layout);            
  
      m_network = new QNetworkAccessManager(this);
      QNetworkRequest request;                    
      request.setRawHeader("Authorization", "Basic " +
                           QByteArray(QString("%1:%2").arg(USER).arg(PASSWORD).toAscii()).toBase64());
      request.setUrl(QUrl(REQUEST_URL));                                                              
      QNetworkReply *reply = m_network->get(request);                                                 
  
      QObject::connect(reply, SIGNAL(downloadProgress(qint64,qint64)),
                              SLOT(slotSetProgress(qint64,qint64)));  
      QObject::connect(m_network, SIGNAL(finished(QNetworkReply *)),  
                                  SLOT(slotRequestFinished(QNetworkReply *)));
  }                                                                           
  
  MainWindow::~MainWindow()
  {                        
  }                        
  
  void MainWindow::slotRequestFinished(QNetworkReply *reply)
  {                                                         
      m_progress->setValue(0);
  
      if (reply->error() > 0) {
          m_label->setText("Error number = " + reply->errorString());
      }
      else {
          QByteArray data = reply->readAll();
          QDomDocument doc;
          doc.setContent(data);
          QDomNodeList nodes = doc.elementsByTagName("message");
  
          if (nodes.size() > 0) {
              m_label->setText(nodes.at(0).toElement().text());
          }
      }
  }
  
  void MainWindow::slotSetProgress(qint64 received, qint64 total)
  {
      if (total > 0 && received > 0) {
          m_progress->setValue((int) total / received);
      }
  }
  
  

• sample.pro

  
  QT       += network xml
  
  TARGET = sample_rest_client
  TEMPLATE = app
  
  
  SOURCES += main.cpp\
          mainwindow.cpp
  
  HEADERS  += mainwindow.h
  
  

• qmake && make && ./sample_rest_client to try it!

2009

04/13

CATEGORY

qt4

TAGS

qt4
rest

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