Qt 模拟 HTTP 表单提交文字或文件到服务器

传统通过 HTTP 表单的方式来上传文件在 Web 中实现是非常简单的，一个表单中加几个域填写上对应的内容提交就可以了，但如果通过 Qt 来实现就相对麻烦一点，不过我都总结好了代码，直接使用就可以了。

需要用到的模块

• QNetworkAccessManager 用来发起 GET/POST 请求
• QNetworkReply 用来描述响应信息
• QHttpMultiPart 用来模拟表单域
• QNetworkRequest 用来构建请求地址等信息

Qt 官方简单例子

Qt 官方基于 QHttpMultiPart 的简单例子：https://doc.qt.io/archives/qt-4.8/qhttpmultipart.html

QHttpMultiPart *multiPart = new QHttpMultiPart(QHttpMultiPart::FormDataType);

QHttpPart textPart;
textPart.setHeader(QNetworkRequest::ContentDispositionHeader, QVariant("form-data; name=\"text\""));
textPart.setBody("my text");

QHttpPart imagePart;
imagePart.setHeader(QNetworkRequest::ContentTypeHeader, QVariant("image/jpeg"));
imagePart.setHeader(QNetworkRequest::ContentDispositionHeader, QVariant("form-data; name=\"image\""));
QFile *file = new QFile("image.jpg");
file->open(QIODevice::ReadOnly);
imagePart.setBodyDevice(file);
file->setParent(multiPart); // we cannot delete the file now, so delete it with the multiPart

multiPart->append(textPart);
multiPart->append(imagePart);

QUrl url("http://my.server.tld");
QNetworkRequest request(url);

QNetworkAccessManager manager;
QNetworkReply *reply = manager.post(request, multiPart);
multiPart->setParent(reply); // delete the multiPart with the reply
// here connect signals etc.

封装后的类

头文件：

#ifndef HTTPUP_LOADER_H
#define HTTPUP_LOADER_H
#include <QObject>
#include <QString>
#include <QByteArray>
#include <QtNetwork/QHttpPart>
#include <QtNetwork/QHttpMultiPart>
#include <QtNetwork/QNetworkReply>
#include <QtNetwork/QNetworkRequest>
#include <QtNetwork/QNetworkAccessManager>

class HttpUploader : public QObject
{
    Q_OBJECT

public:
    HttpUploader(const QString& url, QObject* receiver);
    ~HttpUploader();

    void SetPostURL(const QString& url) { url_ = url; }
    QString GetPostURL() { return url_; }

    bool AddTextField(const QString& key, const QByteArray& value);
    bool AddFileField(const QString& key, const QString& file_path);
    bool PostRequest();
    QNetworkAccessManager* GetNetworkManager() { return net_manager_; }

signals:


private:
    QObject* receiver_;
    QString url_;
    QByteArray post_content_;

    // http upload
    QNetworkAccessManager*  net_manager_ = nullptr;
    QNetworkReply*          net_reply_ = nullptr;

    QHttpMultiPart*         multi_part_ = nullptr;
};

#endif // HTTPUP_LOADER_H

实现文件

#include <QFile>
#include <QUuid>
#include <QFileInfo>

#include "http_uploader.h"

HttpUploader::HttpUploader(const QString& url, QObject* receiver)
    : receiver_(receiver)
    , url_(url)
    , post_content_(QByteArray())
{
    multi_part_ = new QHttpMultiPart(QHttpMultiPart::FormDataType);
    net_manager_ = new QNetworkAccessManager(this);
    connect(net_manager_, SIGNAL(finished(QNetworkReply*)), receiver, SLOT(onNetworkFinished(QNetworkReply*)));
}

HttpUploader::~HttpUploader()
{
    if (multi_part_ != nullptr)
    {
        delete multi_part_;
    }

    if (net_manager_ != nullptr)
    {
        delete net_manager_;
    }
}

bool HttpUploader::AddTextField(const QString &key, const QByteArray &value)
{
    QHttpPart text_part;
    text_part.setHeader(QNetworkRequest::ContentDispositionHeader, QVariant("form-data; name=\"" + key + "\""));
    text_part.setBody(value);

    multi_part_->append(text_part);

    return true;
}

bool HttpUploader::AddFileField(const QString &key, const QString& file_path)
{
    QHttpPart file_part;
    QFileInfo upload_file_info(file_path);
    file_part.setHeader(QNetworkRequest::ContentTypeHeader, QVariant("application/octet-stream"));
    file_part.setHeader(QNetworkRequest::ContentDispositionHeader, QVariant("form-data; name=\"" + key + "\"; filename=\"" + upload_file_info.fileName() + "\""));

    QFile *file = new QFile(file_path);
    file->open(QIODevice::ReadOnly);
    file->setParent(multi_part_);
    file_part.setBodyDevice(file);

    multi_part_->append(file_part);

    return true;
}

bool HttpUploader::PostRequest()
{
    QNetworkRequest request = QNetworkRequest(QUrl(url_));
    net_reply_ = net_manager_->post(request, multi_part_);
    multi_part_->setParent(net_reply_); // delete the multiPart with the reply
    connect(net_reply_, SIGNAL(finished()), receiver_, SLOT(onReplyFinished()));
    connect(net_reply_, SIGNAL(uploadProgress(qint64, qint64)), receiver_, SLOT(onUploadProgress(qint64, qint64)));

    return true;
}

外部调用时，像下面这样调用就可以了

HttpUploader* uploader_ = new HttpUploader(report_url_, this);
uploader_->AddTextField("userId", report_id_.toUtf8());
uploader_->AddTextField("reportContent", comment_.toUtf8());
uploader_->AddFileField("logFile", report_zip_file_);
...
uploader_->PostRequest();

在 new 上传对象的指针时，第二个传递的参数是当前类的一个指针，你需要实现 onNetworkFinished，onReplyFinished，onUploadProgress，来监视上传任务的进度和完成信息，当然你可以自己封装一下，上传对象仅仅提供信号，需要时在外部 connect 就可以了。onNetworkFinished 和 onReplyFinished 的区别是，onReplyFinished 槽函数对应 QNetworkReply 的 finished 信号，他仅仅通知完成了，不会携带任何参数。但是你可以通过 QNetworkReply 的实例对象来获取各种返回值信息。而 onNetworkFinished 槽函数对应的是 QNetworkAccessManager 的 finished 信号，其会携带一个 QNetworkReply 对象指针，你只需要在这里处理返回的对应错误码就可以了。

返回值处理

我使用 QNetworkAccessManager 的 finished 信号来接收完成事件，在 onNetworkFinished 函数中，我们接收到的信息是一个 reply 对象。你可以通过 reply 对象获取 HTTP 返回值：

QVariant variant = reply->attribute(QNetworkRequest::HttpStatusCodeAttribute);
QDebug() << variant.toInt();

也可以打印 Qt 自由的一套返错误代码

qDebug() << reply->error();
qDebug() << reply->errorString();

如果没有错误的情况下，你可以使用 reply 对象获取返回的内容：

qDebug() << reply->readAll();