httpwindow.cpp Example File

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  #include <QtWidgets>
  #include <QtNetwork>
  #include <QUrl>

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

  #if QT_CONFIG(ssl)
  const char defaultUrl[] = "https://www.qt.io/";
  #else
  const char defaultUrl[] = "http://www.qt.io/";
  #endif
  const char defaultFileName[] = "index.html";

  ProgressDialog::ProgressDialog(const QUrl &url, QWidget *parent)
    : QProgressDialog(parent)
  {
      setWindowTitle(tr("Download Progress"));
      setWindowFlags(windowFlags() & ~Qt::WindowContextHelpButtonHint);
      setLabelText(tr("Downloading %1.").arg(url.toDisplayString()));
      setMinimum(0);
      setValue(0);
      setMinimumDuration(0);
      setMinimumSize(QSize(400, 75));
  }

  void ProgressDialog::networkReplyProgress(qint64 bytesRead, qint64 totalBytes)
  {
      setMaximum(totalBytes);
      setValue(bytesRead);
  }

  HttpWindow::HttpWindow(QWidget *parent)
      : QDialog(parent)
      , statusLabel(new QLabel(tr("Please enter the URL of a file you want to download.\n\n"), this))
      , urlLineEdit(new QLineEdit(defaultUrl))
      , downloadButton(new QPushButton(tr("Download")))
      , launchCheckBox(new QCheckBox("Launch file"))
      , defaultFileLineEdit(new QLineEdit(defaultFileName))
      , downloadDirectoryLineEdit(new QLineEdit)
      , reply(nullptr)
      , file(nullptr)
      , httpRequestAborted(false)
  {
      setWindowFlags(windowFlags() & ~Qt::WindowContextHelpButtonHint);
      setWindowTitle(tr("HTTP"));

      connect(&qnam, &QNetworkAccessManager::authenticationRequired,
              this, &HttpWindow::slotAuthenticationRequired);
  #ifndef QT_NO_SSL
      connect(&qnam, &QNetworkAccessManager::sslErrors,
              this, &HttpWindow::sslErrors);
  #endif

      QFormLayout *formLayout = new QFormLayout;
      urlLineEdit->setClearButtonEnabled(true);
      connect(urlLineEdit, &QLineEdit::textChanged,
              this, &HttpWindow::enableDownloadButton);
      formLayout->addRow(tr("&URL:"), urlLineEdit);
      QString downloadDirectory = QStandardPaths::writableLocation(QStandardPaths::TempLocation);
      if (downloadDirectory.isEmpty() || !QFileInfo(downloadDirectory).isDir())
          downloadDirectory = QDir::currentPath();
      downloadDirectoryLineEdit->setText(QDir::toNativeSeparators(downloadDirectory));
      formLayout->addRow(tr("&Download directory:"), downloadDirectoryLineEdit);
      formLayout->addRow(tr("Default &file:"), defaultFileLineEdit);
      launchCheckBox->setChecked(true);
      formLayout->addRow(launchCheckBox);

      QVBoxLayout *mainLayout = new QVBoxLayout(this);
      mainLayout->addLayout(formLayout);

      mainLayout->addItem(new QSpacerItem(0, 0, QSizePolicy::Ignored, QSizePolicy::MinimumExpanding));

      statusLabel->setWordWrap(true);
      mainLayout->addWidget(statusLabel);

      downloadButton->setDefault(true);
      connect(downloadButton, &QAbstractButton::clicked, this, &HttpWindow::downloadFile);
      QPushButton *quitButton = new QPushButton(tr("Quit"));
      quitButton->setAutoDefault(false);
      connect(quitButton, &QAbstractButton::clicked, this, &QWidget::close);
      QDialogButtonBox *buttonBox = new QDialogButtonBox;
      buttonBox->addButton(downloadButton, QDialogButtonBox::ActionRole);
      buttonBox->addButton(quitButton, QDialogButtonBox::RejectRole);
      mainLayout->addWidget(buttonBox);

      urlLineEdit->setFocus();
  }

  void HttpWindow::startRequest(const QUrl &requestedUrl)
  {
      url = requestedUrl;
      httpRequestAborted = false;

      reply = qnam.get(QNetworkRequest(url));
      connect(reply, &QNetworkReply::finished, this, &HttpWindow::httpFinished);
      connect(reply, &QIODevice::readyRead, this, &HttpWindow::httpReadyRead);

      ProgressDialog *progressDialog = new ProgressDialog(url, this);
      progressDialog->setAttribute(Qt::WA_DeleteOnClose);
      connect(progressDialog, &QProgressDialog::canceled, this, &HttpWindow::cancelDownload);
      connect(reply, &QNetworkReply::downloadProgress, progressDialog, &ProgressDialog::networkReplyProgress);
      connect(reply, &QNetworkReply::finished, progressDialog, &ProgressDialog::hide);
      progressDialog->show();

      statusLabel->setText(tr("Downloading %1...").arg(url.toString()));
  }

  void HttpWindow::downloadFile()
  {
      const QString urlSpec = urlLineEdit->text().trimmed();
      if (urlSpec.isEmpty())
          return;

      const QUrl newUrl = QUrl::fromUserInput(urlSpec);
      if (!newUrl.isValid()) {
          QMessageBox::information(this, tr("Error"),
                                   tr("Invalid URL: %1: %2").arg(urlSpec, newUrl.errorString()));
          return;
      }

      QString fileName = newUrl.fileName();
      if (fileName.isEmpty())
          fileName = defaultFileLineEdit->text().trimmed();
      if (fileName.isEmpty())
          fileName = defaultFileName;
      QString downloadDirectory = QDir::cleanPath(downloadDirectoryLineEdit->text().trimmed());
      bool useDirectory = !downloadDirectory.isEmpty() && QFileInfo(downloadDirectory).isDir();
      if (useDirectory)
          fileName.prepend(downloadDirectory + '/');
      if (QFile::exists(fileName)) {
          if (QMessageBox::question(this, tr("Overwrite Existing File"),
                                    tr("There already exists a file called %1%2."
                                       " Overwrite?")
                                       .arg(fileName,
                                            useDirectory
                                             ? QString()
                                             : QStringLiteral(" in the current directory")),
                                       QMessageBox::Yes | QMessageBox::No,
                                       QMessageBox::No)
              == QMessageBox::No) {
              return;
          }
          QFile::remove(fileName);
      }

      file = openFileForWrite(fileName);
      if (!file)
          return;

      downloadButton->setEnabled(false);

      // schedule the request
      startRequest(newUrl);
  }

  QFile *HttpWindow::openFileForWrite(const QString &fileName)
  {
      QScopedPointer<QFile> file(new QFile(fileName));
      if (!file->open(QIODevice::WriteOnly)) {
          QMessageBox::information(this, tr("Error"),
                                   tr("Unable to save the file %1: %2.")
                                   .arg(QDir::toNativeSeparators(fileName),
                                        file->errorString()));
          return nullptr;
      }
      return file.take();
  }

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

  void HttpWindow::httpFinished()
  {
      QFileInfo fi;
      if (file) {
          fi.setFile(file->fileName());
          file->close();
          delete file;
          file = nullptr;
      }

      if (httpRequestAborted) {
          reply->deleteLater();
          reply = nullptr;
          return;
      }

      if (reply->error()) {
          QFile::remove(fi.absoluteFilePath());
          statusLabel->setText(tr("Download failed:\n%1.").arg(reply->errorString()));
          downloadButton->setEnabled(true);
          reply->deleteLater();
          reply = nullptr;
          return;
      }

      const QVariant redirectionTarget = reply->attribute(QNetworkRequest::RedirectionTargetAttribute);

      reply->deleteLater();
      reply = nullptr;

      if (!redirectionTarget.isNull()) {
          const QUrl redirectedUrl = url.resolved(redirectionTarget.toUrl());
          if (QMessageBox::question(this, tr("Redirect"),
                                    tr("Redirect to %1 ?").arg(redirectedUrl.toString()),
                                    QMessageBox::Yes | QMessageBox::No) == QMessageBox::No) {
              QFile::remove(fi.absoluteFilePath());
              downloadButton->setEnabled(true);
              statusLabel->setText(tr("Download failed:\nRedirect rejected."));
              return;
          }
          file = openFileForWrite(fi.absoluteFilePath());
          if (!file) {
              downloadButton->setEnabled(true);
              return;
          }
          startRequest(redirectedUrl);
          return;
      }

      statusLabel->setText(tr("Downloaded %1 bytes to %2\nin\n%3")
                           .arg(fi.size()).arg(fi.fileName(), QDir::toNativeSeparators(fi.absolutePath())));
      if (launchCheckBox->isChecked())
          QDesktopServices::openUrl(QUrl::fromLocalFile(fi.absoluteFilePath()));
      downloadButton->setEnabled(true);
  }

  void HttpWindow::httpReadyRead()
  {
      // this slot gets called every time the QNetworkReply has new data.
      // We read all of its new data and write it into the file.
      // That way we use less RAM than when reading it at the finished()
      // signal of the QNetworkReply
      if (file)
          file->write(reply->readAll());
  }

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

  void HttpWindow::slotAuthenticationRequired(QNetworkReply *, QAuthenticator *authenticator)
  {
      QDialog authenticationDialog;
      Ui::Dialog ui;
      ui.setupUi(&authenticationDialog);
      authenticationDialog.adjustSize();
      ui.siteDescription->setText(tr("%1 at %2").arg(authenticator->realm(), url.host()));

      // Did the URL have information? Fill the UI
      // This is only relevant if the URL-supplied credentials were wrong
      ui.userEdit->setText(url.userName());
      ui.passwordEdit->setText(url.password());

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

  #ifndef QT_NO_SSL
  void HttpWindow::sslErrors(QNetworkReply *, const QList<QSslError> &errors)
  {
      QString errorString;
      foreach (const QSslError &error, errors) {
          if (!errorString.isEmpty())
              errorString += '\n';
          errorString += error.errorString();
      }

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