使用Qt的网络模块API实现多个URL下载的命令行工具。
源码
本文的「网络下载器」共有两个版本，分别是「原始版本」和「升级版本」。下列源码是原始版本代码，而升级版本新增了下载进度和增强代码的健壮性。
代码语言：javascript复制/****************************************************************************
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#include <QtCore>
#include <QtNetwork>
#include <cstdio>
QT_BEGIN_NAMESPACE
class QSslError;
QT_END_NAMESPACE
using namespace std;
class DownloadManager: public QObject
{
Q_OBJECT
QNetworkAccessManager manager;
QVector<QNetworkReply *> currentDownloads;
public:
DownloadManager();
void doDownload(const QUrl &url);
static QString saveFileName(const QUrl &url);
bool saveToDisk(const QString &filename, QIODevice *data);
static bool isHttpRedirect(QNetworkReply *reply);
public slots:
void execute();
void downloadFinished(QNetworkReply *reply);
void sslErrors(const QList<QSslError> &errors);
};
DownloadManager::DownloadManager()
{
connect(&manager, SIGNAL(finished(QNetworkReply*)),
SLOT(downloadFinished(QNetworkReply*)));
}
void DownloadManager::doDownload(const QUrl &url)
{
QNetworkRequest request(url);
QNetworkReply *reply = manager.get(request);
#if QT_CONFIG(ssl)
connect(reply, SIGNAL(sslErrors(QList<QSslError>)),
SLOT(sslErrors(QList<QSslError>)));
#endif
currentDownloads.append(reply);
}
QString DownloadManager::saveFileName(const QUrl &url)
{
QString path = url.path();
QString basename = QFileInfo(path).fileName();
if (basename.isEmpty())
basename = "download";
if (QFile::exists(basename)) {
// already exists, don't overwrite
int i = 0;
basename = '.';
while (QFile::exists(basename QString::number(i)))
i;
basename = QString::number(i);
}
return basename;
}
bool DownloadManager::saveToDisk(const QString &filename, QIODevice *data)
{
QFile file(filename);
if (!file.open(QIODevice::WriteOnly)) {
fprintf(stderr, "Could not open %s for writing: %sn",
qPrintable(filename),
qPrintable(file.errorString()));
return false;
}
file.write(data->readAll());
file.close();
return true;
}
bool DownloadManager::isHttpRedirect(QNetworkReply *reply)
{
int statusCode = reply->attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt();
return statusCode == 301 || statusCode == 302 || statusCode == 303
|| statusCode == 305 || statusCode == 307 || statusCode == 308;
}
void DownloadManager::execute()
{
QStringList args = QCoreApplication::instance()->arguments();
args.takeFirst(); // skip the first argument, which is the program's name
if (args.isEmpty()) {
printf("Qt Download example - downloads all URLs in paralleln"
"Usage: download url1 [url2... urlN]n"
"n"
"Downloads the URLs passed in the command-line to the local directoryn"
"If the target file already exists, a .0, .1, .2, etc. is appended ton"
"differentiate.n");
QCoreApplication::instance()->quit();
return;
}
for (const QString &arg : qAsConst(args)) {
QUrl url = QUrl::fromEncoded(arg.toLocal8Bit());
doDownload(url);
}
}
void DownloadManager::sslErrors(const QList<QSslError> &sslErrors)
{
#if QT_CONFIG(ssl)
for (const QSslError &error : sslErrors)
fprintf(stderr, "SSL error: %sn", qPrintable(error.errorString()));
#else
Q_UNUSED(sslErrors);
#endif
}
void DownloadManager::downloadFinished(QNetworkReply *reply)
{
QUrl url = reply->url();
if (reply->error()) {
fprintf(stderr, "Download of %s failed: %sn",
url.toEncoded().constData(),
qPrintable(reply->errorString()));
} else {
if (isHttpRedirect(reply)) {
fputs("Request was redirected.n", stderr);
} else {
QString filename = saveFileName(url);
if (saveToDisk(filename, reply)) {
printf("Download of %s succeeded (saved to %s)n",
url.toEncoded().constData(), qPrintable(filename));
}
}
}
currentDownloads.removeAll(reply);
reply->deleteLater();
if (currentDownloads.isEmpty()) {
// all downloads finished
QCoreApplication::instance()->quit();
}
}
int main(int argc, char **argv)
{
QCoreApplication app(argc, argv);
DownloadManager manager;
QTimer::singleShot(0, &manager, SLOT(execute()));
app.exec();
}
#include "main.moc"
关于更多
- 在「QtCreator软件」可以找到：
- 或在以下「Qt安装目录」找到：
版本1(原始版本)：
代码语言：javascript复制C:Qt{你的Qt版本}Examples{你的Qt版本}networkdownload版本2(升级版本)：
代码语言：javascript复制C:Qt{你的Qt版本}Examples{你的Qt版本}networkdownloadmanager- 「相关链接」
版本1(原始版本)：
代码语言：javascript复制https://doc.qt.io/qt-5/qtnetwork-download-example.html版本2(升级版本)：
代码语言：javascript复制https://doc.qt.io/qt-5/qtnetwork-downloadmanager-example.html
