QNetworkReply和301重定向

Question

QNetworkReply和301重定向

12

我有一个WebViewer，只想让它能够访问我们的Web应用程序。为了实现这一点，我已经放置了一个PHP头文件，并在我的Qt App中查找它。这个方法很好用，但有一个例外，就是301永久移动状态代码。现代浏览器会自动重定向，但在HTTP请求末尾加上“/”。

当输入我们Web应用程序的URL时，目前需要添加斜杠才能检测到头文件，但我希望即使没有斜杠，也能够获取该头文件。

以下是我目前检索头文件的方法：

QNetworkAccessManager *manager = new QNetworkAccessManager(this);
    QNetworkRequest request;
    request.setUrl(url);
    connect(manager, SIGNAL(finished(QNetworkReply*)), this, SLOT(onFinished(QNetworkReply*)));

    request.setRawHeader("User-Agent", "CytoViewer 1.0");
    request.setHeader(QNetworkRequest::ContentTypeHeader,"application/CytoViewer");
    QNetworkReply *reply = manager->get(request);
    reply->ignoreSslErrors();
    QEventLoop loop;

    connect(reply, SIGNAL(finished()), &loop, SLOT(quit()));
    loop.exec();
    qDebug() << "QLoop reply all: " << reply->readAll();
    qDebug() << "QLoop: " << reply->rawHeader("Cyto-Study-Manager");
    if(reply->rawHeader("OurWebApp") == "1"){
        //Header exists?(QEventLoop finish) Set arg[1]"url 'Found prouct: product header'"
        product = reply->rawHeader("Product");
        return true;
    } else {
        //Header doen't exist? Graceful error - not a valid PI product
        return false;
    }

为了解决301跳转问题，我发送了两个网络请求。第一个请求访问输入的URL并检查状态码是否为301。如果状态码为301，则使用reply->attribute(QNetworkRequest::RedirectionTargetAttribute).toUrl();方法获取建议的URL，并返回该URL；否则，如果没有状态码，则简单地返回用户输入的上一个URL，然后发送另一个网络请求以检查标头。

第一个请求是我发送的，用于检查状态码：

QUrl MainWindow::networkRequest(QUrl checkUrl){
    qDebug() << "checkURL: " << checkUrl;
    //
    QNetworkAccessManager *manager = new QNetworkAccessManager(this);
    QNetworkRequest request;
    request.setUrl(checkUrl);
    request.setRawHeader("User-Agent", "CytoViewer 1.0");
    request.setHeader(QNetworkRequest::ContentTypeHeader,"application/CytoViewer");
    QNetworkReply *reply = manager->get(request);
    reply->ignoreSslErrors();
    QEventLoop checkLoop;
    connect(reply, SIGNAL(finished()), &checkLoop, SLOT(quit()));
    checkLoop.exec();
    //Check status code
    if (reply->error() == QNetworkReply::NoError) {
        int statusCode = reply->attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt();
        if(statusCode == 301) {
            QUrl redirectUrl = reply->attribute(QNetworkRequest::RedirectionTargetAttribute).toUrl();
            return redirectUrl;
        }else {
            return checkUrl;
        }

    }
}

长话短说，我正在发送两个网络请求，1）检查301 2）检查我们的应用程序头文件。

有没有办法在一个请求中完成这个操作？我是否错过了一个可以自动重定向的方法？

问候，

Nathan

- Kal

2个回答

12

显然没有。

这里有一篇官方的HOWTO入门文章，介绍如何使用QNetworkAccessManager处理HTTP重定向：https://web.archive.org/web/20141101060340/http://developer.nokia.com/community/wiki/Handling_an_HTTP_redirect_with_QNetworkAccessManager 以下是上述链接中的摘录：

void QNAMRedirect::replyFinished(QNetworkReply* reply) {
    /*
     * Reply is finished!
     * We'll ask for the reply about the Redirection attribute
     * http://doc.trolltech.com/qnetworkrequest.html#Attribute-enum
     */
    QVariant possibleRedirectUrl =
             reply->attribute(QNetworkRequest::RedirectionTargetAttribute);
 
    /* We'll deduct if the redirection is valid in the redirectUrl function */
    _urlRedirectedTo = this->redirectUrl(possibleRedirectUrl.toUrl(),
                                         _urlRedirectedTo);
 
    /* If the URL is not empty, we're being redirected. */
    if(!_urlRedirectedTo.isEmpty()) {
        QString text = QString("QNAMRedirect::replyFinished: Redirected to ")
                              .append(_urlRedirectedTo.toString());
        this->_textContainer->setText(text);
 
        /* We'll do another request to the redirection url. */
        this->_qnam->get(QNetworkRequest(_urlRedirectedTo));
    }
    else {
        /*
         * We weren't redirected anymore
         * so we arrived to the final destination...
         */
        QString text = QString("QNAMRedirect::replyFinished: Arrived to ")
                              .append(reply->url().toString());
        this->_textContainer->setText(text);
        /* ...so this can be cleared. */
        _urlRedirectedTo.clear();
    }
    /* Clean up. */
    reply->deleteLater();
}
 
QUrl QNAMRedirect::redirectUrl(const QUrl& possibleRedirectUrl,
                               const QUrl& oldRedirectUrl) const {
    QUrl redirectUrl;
    /*
     * Check if the URL is empty and
     * that we aren't being fooled into a infinite redirect loop.
     * We could also keep track of how many redirects we have been to
     * and set a limit to it, but we'll leave that to you.
     */
    if(!possibleRedirectUrl.isEmpty() &&
       possibleRedirectUrl != oldRedirectUrl) {
        redirectUrl = possibleRedirectUrl;
    }
    return redirectUrl;
}

- kfunk

我曾经认为可能没有办法，但不确定是否有什么地方我错过了什么，感谢@kfunk的澄清 :) - Kal

1

官方HOWTO的链接已经失效了:( - David Sánchez

@DavidSánchez：已更新评论以反映此事。不幸的是，在其被删除之前，维基内容尚未移动 :( - kfunk

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原文链接

- Konrad · Accepted Answer

如果您正在使用Qt 6，则可以跳过阅读本答案，因为自动重定向是默认行为

如果您未使用Qt 6，则旧的答案如下：

Qt 5.6添加了自动重定向支持（QNetworkRequest::FollowRedirectsAttribute）。

默认情况下它未启用：

QNetworkRequest req(QUrl("https://example.com/"));
req.setAttribute(QNetworkRequest::FollowRedirectsAttribute, true);