httpwindow.cpp Example File
network/http/httpwindow.cpp

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 #include <QtGui>
 #include <QtNetwork>

 #include "httpwindow.h"
 #include "ui_authenticationdialog.h"

 HttpWindow::HttpWindow(QWidget *parent)
     : QDialog(parent)
 {
 #ifndef QT_NO_OPENSSL
     urlLineEdit = new QLineEdit("https://");
 #else
     urlLineEdit = new QLineEdit("http://");
 #endif

     urlLabel = new QLabel(tr("&URL:"));
     urlLabel->setBuddy(urlLineEdit);
     statusLabel = new QLabel(tr("Please enter the URL of a file you want to "
                                 "download."));

     downloadButton = new QPushButton(tr("Download"));
     downloadButton->setDefault(true);
     quitButton = new QPushButton(tr("Quit"));
     quitButton->setAutoDefault(false);

     buttonBox = new QDialogButtonBox;
     buttonBox->addButton(downloadButton, QDialogButtonBox::ActionRole);
     buttonBox->addButton(quitButton, QDialogButtonBox::RejectRole);

     progressDialog = new QProgressDialog(this);

     http = new QHttp(this);

     connect(urlLineEdit, SIGNAL(textChanged(const QString &)),
             this, SLOT(enableDownloadButton()));
     connect(http, SIGNAL(requestFinished(int, bool)),
             this, SLOT(httpRequestFinished(int, bool)));
     connect(http, SIGNAL(dataReadProgress(int, int)),
             this, SLOT(updateDataReadProgress(int, int)));
     connect(http, SIGNAL(responseHeaderReceived(const QHttpResponseHeader &)),
             this, SLOT(readResponseHeader(const QHttpResponseHeader &)));
     connect(http, SIGNAL(authenticationRequired(const QString &, quint16, QAuthenticator *)),
             this, SLOT(slotAuthenticationRequired(const QString &, quint16, QAuthenticator *)));
 #ifndef QT_NO_OPENSSL
     connect(http, SIGNAL(sslErrors(const QList<QSslError> &)),
             this, SLOT(sslErrors(const QList<QSslError> &)));
 #endif
     connect(progressDialog, SIGNAL(canceled()), this, SLOT(cancelDownload()));
     connect(downloadButton, SIGNAL(clicked()), this, SLOT(downloadFile()));
     connect(quitButton, SIGNAL(clicked()), this, SLOT(close()));

     QHBoxLayout *topLayout = new QHBoxLayout;
     topLayout->addWidget(urlLabel);
     topLayout->addWidget(urlLineEdit);

     QVBoxLayout *mainLayout = new QVBoxLayout;
     mainLayout->addLayout(topLayout);
     mainLayout->addWidget(statusLabel);
     mainLayout->addWidget(buttonBox);
     setLayout(mainLayout);

     setWindowTitle(tr("HTTP"));
     urlLineEdit->setFocus();
 }

 void HttpWindow::downloadFile()
 {
     QUrl url(urlLineEdit->text());
     QFileInfo fileInfo(url.path());
     QString fileName = fileInfo.fileName();
     if (fileName.isEmpty())
         fileName = "index.html";

     if (QFile::exists(fileName)) {
         if (QMessageBox::question(this, tr("HTTP"),
                                   tr("There already exists a file called %1 in "
                                      "the current directory. Overwrite?").arg(fileName),
                                   QMessageBox::Yes|QMessageBox::No, QMessageBox::No)
             == QMessageBox::No)
             return;
         QFile::remove(fileName);
     }

     file = new QFile(fileName);
     if (!file->open(QIODevice::WriteOnly)) {
         QMessageBox::information(this, tr("HTTP"),
                                  tr("Unable to save the file %1: %2.")
                                  .arg(fileName).arg(file->errorString()));
         delete file;
         file = 0;
         return;
     }

     QHttp::ConnectionMode mode = url.scheme().toLower() == "https" ? QHttp::ConnectionModeHttps : QHttp::ConnectionModeHttp;
     http->setHost(url.host(), mode, url.port() == -1 ? 0 : url.port());

     if (!url.userName().isEmpty())
         http->setUser(url.userName(), url.password());

     httpRequestAborted = false;
     QByteArray path = QUrl::toPercentEncoding(url.path(), "!$&'()*+,;=:@/");
     if (path.isEmpty())
         path = "/";
     httpGetId = http->get(path, file);

     progressDialog->setWindowTitle(tr("HTTP"));
     progressDialog->setLabelText(tr("Downloading %1.").arg(fileName));
     downloadButton->setEnabled(false);
 }

 void HttpWindow::cancelDownload()
 {
     statusLabel->setText(tr("Download canceled."));
     httpRequestAborted = true;
     http->abort();
     downloadButton->setEnabled(true);
 }

 void HttpWindow::httpRequestFinished(int requestId, bool error)
 {
     if (requestId != httpGetId)
         return;
     if (httpRequestAborted) {
         if (file) {
             file->close();
             file->remove();
             delete file;
             file = 0;
         }

         progressDialog->hide();
         return;
     }

     if (requestId != httpGetId)
         return;

     progressDialog->hide();
     file->close();

     if (error) {
         file->remove();
         QMessageBox::information(this, tr("HTTP"),
                                  tr("Download failed: %1.")
                                  .arg(http->errorString()));
     } else {
         QString fileName = QFileInfo(QUrl(urlLineEdit->text()).path()).fileName();
         statusLabel->setText(tr("Downloaded %1 to current directory.").arg(fileName));
     }

     downloadButton->setEnabled(true);
     delete file;
     file = 0;
 }

 void HttpWindow::readResponseHeader(const QHttpResponseHeader &responseHeader)
 {
     switch (responseHeader.statusCode()) {
     case 200:                   // Ok
     case 301:                   // Moved Permanently
     case 302:                   // Found
     case 303:                   // See Other
     case 307:                   // Temporary Redirect
         // these are not error conditions
         break;

     default:
         QMessageBox::information(this, tr("HTTP"),
                                  tr("Download failed: %1.")
                                  .arg(responseHeader.reasonPhrase()));
         httpRequestAborted = true;
         progressDialog->hide();
         http->abort();
     }
 }

 void HttpWindow::updateDataReadProgress(int bytesRead, int totalBytes)
 {
     if (httpRequestAborted)
         return;

     progressDialog->setMaximum(totalBytes);
     progressDialog->setValue(bytesRead);
 }

 void HttpWindow::enableDownloadButton()
 {
     downloadButton->setEnabled(!urlLineEdit->text().isEmpty());
 }

 void HttpWindow::slotAuthenticationRequired(const QString &hostName, quint16, QAuthenticator *authenticator)
 {
     QDialog dlg;
     Ui::Dialog ui;
     ui.setupUi(&dlg);
     dlg.adjustSize();
     ui.siteDescription->setText(tr("%1 at %2").arg(authenticator->realm()).arg(hostName));

     if (dlg.exec() == QDialog::Accepted) {
         authenticator->setUser(ui.userEdit->text());
         authenticator->setPassword(ui.passwordEdit->text());
     }
 }

 #ifndef QT_NO_OPENSSL
 void HttpWindow::sslErrors(const QList<QSslError> &errors)
 {
     QString errorString;
     foreach (const QSslError &error, errors) {
         if (!errorString.isEmpty())
             errorString += ", ";
         errorString += error.errorString();
     }

     if (QMessageBox::warning(this, tr("HTTP Example"),
                              tr("One or more SSL errors has occurred: %1").arg(errorString),
                              QMessageBox::Ignore | QMessageBox::Abort) == QMessageBox::Ignore) {
         http->ignoreSslErrors();
     }
 }
 #endif