在本地生成 html 文件，双击打开进入网页，网上找的代码，记录一下

[1] MyHttp.pro 添加 network

# [1]添加 network
QT += network
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[2] mainwindow.h 添加头文件

// [2] 添加头文件
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
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[3] mainwindow.h 添加私有对象

// [3] 添加对象
private:
	QUrl url;
	QNetworkRequest req;
	QNetworkReply *reply;
	QNetworkAccessManager *manager;
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[4] mainwindow.h 声明槽

// [4]声明槽
private slots:
    void startRequest(const QUrl &requestedUrl);
    void replyFinished();
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[5] mainwindow.c

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    // [5]发送http请求
    startRequest( QUrl("http://www.baidu.com"));
}

MainWindow::~MainWindow()
{
    delete ui;
}

// [6]发起HTTP请求
/*
 * 功能描述：发送HTTP请求，并与请求响应的槽绑定
 *  @param requestedUrl：请求需要的URL地址
*/
void MainWindow::startRequest(const QUrl &requestedUrl){
    url = requestedUrl;
    manager = new QNetworkAccessManager(this);
    req.setUrl(url);
    qDebug() << "setUrl ok";
    req.setAttribute(QNetworkRequest::FollowRedirectsAttribute, true);
    qDebug() << "setAttribute ok";
    req.setRawHeader("Accept","text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9");
    qDebug() << "setRawHeader ok";
    req.setRawHeader("User-Agent","Mozilla/5.0 (Windows NT 10.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.198 Safari/537.36");
    qDebug() << "setRawHeader ok";
    reply = manager->get(req);
    qDebug() << "reply...";
    connect(reply,&QNetworkReply::finished,this,&MainWindow::replyFinished);
}

// [7]获取HTTP的请求响应
/*
 * 功能描述：HTTP请求后，接收服务器的请求信息
 * 1 检测请求响应是否有错误
 * 2 获取请求响应的状态码
 * 3 判断是否需要重定向
 *   - 不需要，则保存数据
 *   - 需要重定向，则获取重定向的URL，然后通过这个URL再次发起请求
*/
void MainWindow::replyFinished(){
    qDebug() << "replyFinished";
    // <1>判断有没有错误
    if (reply->error()){
        qDebug()<<"reply error:" << reply->errorString();
        reply->deleteLater();
        return;
    }

    // <2>检测状态码
    int statusCode  = reply->attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt();
    qDebug() << "statusCode:" << statusCode;

    // <3>判断是否需要重定向
    if (statusCode >= 200 && statusCode <300){
        // ok

        // 准备读数据
        QTextCodec *codec = QTextCodec::codecForName("utf8");
        QString all = codec->toUnicode(reply->readAll());
        qDebug() << "codec to Unicode:" << all;


        // 保存HTTP响应内容
        // 组装保存的文件名 文件名格式： 路径/年_月_日 小时_分_秒 httpfile.html
        QDateTime current_date_time =QDateTime::currentDateTime();
        QString current_date =current_date_time.toString("yyyy_MM_dd hh_mm_ss");
        QString filePath = QApplication::applicationDirPath() + QStringLiteral("/httpDoc");
        QString fileName = filePath + '/' + current_date + " httpfile" + ".html";
        qDebug() << fileName;

        QFile file(fileName);
        if (!file.open(QIODevice::ReadWrite | QIODevice::Text)){
            qDebug() << "file open error!";
            return ;
        }
        QTextStream out(&file);
        out.setCodec("UTF-8");
        out<<all << endl;
        file.close();


        // 数据读取完成之后，清除reply
        reply->deleteLater();
        reply = nullptr;

    } else if (statusCode >=300 && statusCode <400){
        // redirect

        // 获取重定向信息
        const QVariant redirectionTarget = reply->attribute(QNetworkRequest::RedirectionTargetAttribute);
        // 检测是否需要重定向，如果不需要则读数据
        if (!redirectionTarget.isNull()) {
            const QUrl redirectedUrl = url.resolved(redirectionTarget.toUrl());

            reply->deleteLater();
            reply = nullptr;

            startRequest(redirectedUrl);
            qDebug()<< "http redirect to " << redirectedUrl.toString();
            return;
        }
    }
}
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编译运行提示错误

qt.network.ssl: QSslSocket: cannot call unresolved function SSLv23_client_method
qt.network.ssl: QSslSocket: cannot call unresolved function SSL_CTX_new
qt.network.ssl: QSslSocket: cannot call unresolved function SSL_library_init
qt.network.ssl: QSslSocket: cannot call unresolved function ERR_get_error
qt.network.ssl: QSslSocket: cannot call unresolved function ERR_get_error
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解决方法

D:\Qt\Qt5.9.4\Tools\QtCreator\bin 目录下的 libeay32.dll ssleay32.dll 复制到 D:\Qt\Qt5.9.4\5.9.4\msvc2015\bin 目录下，直接编译运行 OK