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();

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