C++ Qt 学习（六）：Qt http 编程

1. http 基础

• HTTP 基础教程
• C++ Web 框架
  • drogon
  • oatpp

2. C++ Qt 用户登录、注册功能实现

• login_register.h

#pragma once

#include 
#include "ui_login_register.h"
#include 

class login_register : public QDialog {
    Q_OBJECT

public:
    login_register(QWidget *parent = Q_NULLPTR);

private:
    void test_http_post();
    void test_timeout_http_post();

private slots:
    void on_btnLogin_clicked();
    void post_requestFinished(QNetworkReply* reply);

private:
    Ui::login_registerClass ui;
};

• login_register.cpp

#pragma execution_character_set("utf-8")

#include "login_register.h"

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

login_register::login_register(QWidget *parent) : QDialog(parent) {
    ui.setupUi(this);
}

void login_register::on_btnLogin_clicked() {
    //test_http_post();
    test_timeout_http_post();
}

void login_register::test_http_post() {
    QNetworkAccessManager* pHttpMgr = new QNetworkAccessManager();

    // 设置 url
    QString url = "http://127.0.0.1:8080/login";

    // 设置头信息
    QNetworkRequest requestInfo;
    requestInfo.setUrl(QUrl(url));
    requestInfo.setHeader(QNetworkRequest::ContentTypeHeader, QVariant("application/json"));

    // setRawData
    QJsonObject rawJson;
    rawJson.insert("username", "zhangsan");
    rawJson.insert("password", "123456");

    QByteArray byte_array = QJsonDocument(rawJson).toJson();
  
    // 发送 post 请求
    QNetworkReply* reply = pHttpMgr->post(requestInfo, byte_array);

    if (reply) {
        // 添加事件循环机制，返回后再运行后面的
        connect(pHttpMgr, &QNetworkAccessManager::finished, 
            this, &login_register::post_requestFinished);
    }
}

void login_register::post_requestFinished(QNetworkReply* reply) {
    // 获取 http 状态码
    QVariant statusCode = reply->attribute(QNetworkRequest::HttpStatusCodeAttribute);
    if (statusCode.isValid())
        qDebug() << "status code=" << statusCode.toInt();

    QVariant reason = reply->attribute(QNetworkRequest::HttpReasonPhraseAttribute).toString();
    if (reason.isValid())
        qDebug() << "reason=" << reason.toString();

    QNetworkReply::NetworkError err = reply->error();

    if (err != QNetworkReply::NoError) {
        // 请求失败
        QVariant statusCode = reply->attribute(QNetworkRequest::HttpStatusCodeAttribute);

        QMessageBox::information(this, "warn",
            "http post failed, error code = " + statusCode.toString() + " error info: " + reply->errorString());

        return;
    } else {
        // 请求成功
        // 接收请求结果
        QByteArray responseByte = reply->readAll();
        QString strRes = responseByte;

        QMessageBox::information(this, "http post success",
            "post response = " + strRes);
    }
}

void login_register::test_timeout_http_post() {
    QNetworkAccessManager* pHttpMgr = new QNetworkAccessManager();

    // 设置 url
    QString url = "http://127.0.0.1:8080/login";

    // 设置头信息
    QNetworkRequest requestInfo;
    requestInfo.setUrl(QUrl(url));
    requestInfo.setHeader(QNetworkRequest::ContentTypeHeader, QVariant("application/json"));

    // setRawData
    QJsonObject rawJson;
    rawJson.insert("username", "zhangsan");
    rawJson.insert("password", "123456");

    QByteArray byte_array = QJsonDocument(rawJson).toJson();

    // 发送 post 请求
    QNetworkReply* reply = pHttpMgr->post(requestInfo, byte_array);

    // 添加超时处理，1ms 超时
    QEventLoop eventloop;
    connect(reply, SIGNAL(finished()), &eventloop, SLOT(quit()));

    // 比如设置 1ms 内完成请求，否则就认为是超时
    QTimer::singleShot(1000, &eventloop, &QEventLoop::quit);
    eventloop.exec();

    QByteArray array;
    if (reply->isFinished()) {
        if (reply->error() == QNetworkReply::NoError) {
            // 正常结束，读取响应数据
            QByteArray result = reply->readAll();
            QString strRes = result;

            QMessageBox::information(this, "http post success",
                "post response = " + strRes);
        } else {
            // 异常结束
            // 请求失败
            QVariant statusCode = reply->attribute(QNetworkRequest::HttpStatusCodeAttribute);

            QMessageBox::information(this, "warn",
                "http post failed, error code = " + statusCode.toString() + " error info: " + reply->errorString());

            return;
        }
    } else {
        // 请求超时
        disconnect(reply, &QNetworkReply::finished, &eventloop, &QEventLoop::quit);
        reply->abort();
        
        QMessageBox::information(this, "http post timeout", "http post timeout");
    }

    reply->deleteLater();
}

3. Qt json 解析介绍

• ch65_qtjson.cpp

#include "ch65_qtjson.h"
#include 
#include  
#include 
#include 

using namespace std;

ch65_qtjson::ch65_qtjson(QWidget *parent) : QWidget(parent) {
    ui.setupUi(this);

    /*string json_str = R"(
        {
            "date": "20220701",
            "level": 1,
            "msg": "register account",
            "status": "success",
            "username": "jackli"
        }
    )";*/

    string json_str = R"({})";

    QString qstr = QString::fromStdString(json_str);

    if (qstr.isEmpty()) {
        qDebug() << "qstr is empty";
        return;
    }

    QByteArray jbyte = qstr.toLocal8Bit();
    // 捕获转换过程中出现的错误
    QJsonParseError error;
    QJsonDocument jdoc = QJsonDocument::fromJson(jbyte, &error);

    if (error.error != QJsonParseError::NoError) {
        // 有错误
        qDebug() << "json parse error";
        return;
    }
    qDebug() << "json parse success";

    if (jdoc.isNull() || jdoc.isEmpty()) {
        qDebug() << "json docment is empty";
        return;
    }

    QJsonObject jobj = jdoc.object();
    QString date = jobj["date"].toString();
    qDebug() << "date" << date;

    int level = jobj["level"].toInt();
    qDebug() << "level" << level;
}

ch65_qtjson::~ch65_qtjson() {}

4. C++ nlohmann::json 使用介绍

• nlohmann::json

• Qt 有 json 解析相关的类，但不推荐使用，建议使用 nlohmann::json，这个 json 适用于任何 C++ 框架

• nlohmann::json 只需要一个头文件 json.hpp，不需要编译成 lib，直接放到项目中即可使用

• main.cpp

#include 
#include "json.hpp"
#include 

using json_t = nlohmann::json;

using namespace std;

int parse_array() {
    string jsonstr = R"(
        {
            "id":"2022",
            "name":{"EnglishName":"JackMa"},
            "title":[
                {
                    "company":"taobao", 
                    "position" : "AAA", 
                    "salary" : "10000"
                },
                { 
                    "company":"zhifubao",
                    "position" : "CCC",
                    "salary" : "890898" 
                },
                { 
                    "company":"pingtouge",
                    "position" : "KKK",
                    "salary" : "76843" 
                }
            ]
        }
    )";

    try {
        json_t jsonObj = json_t::parse(jsonstr);

        // 取出 name
        json_t nameJson = jsonObj["name"];
        string engName = nameJson["EnglishName"];
        cout << "engName = " << engName << endl;

        // 取出 title
        json_t titleJson = jsonObj["title"];
        int size = titleJson.size();
        cout << "size = " << size << endl;

        for (auto jsonItem : titleJson) {
            cout << jsonItem["company"] << endl;
            cout << jsonItem["position"] << endl;
            cout << jsonItem["salary"] << endl;
        }
    } catch (const std::exception&) {
        return -1;
    }

    return 0;
}

int main() {
    /* 序列化，把 json 数据转成 string */
    json_t jRawdata;
    jRawdata["username"] = "jackli";
    jRawdata["pwd"] = "123456";

    // nlohmann::json 中的 dump 方法实现数据转储
    string _rawdata = jRawdata.dump(4);
    cout << _rawdata << endl; 

    /* 反序列化，把 string 数据转成 json */
    string json_str = R"(
        {
            "date": "20220701",
            "level": 1,
            "msg": "register account",
            "status": "success",
            "username": "jackli"
        }
    )";

    try  {
        json_t j2 = json_t::parse(json_str);
        string date = j2["date"];
        cout << date << endl;
    } catch (std::exception& e) {
        cout << "json parse failed" << endl;
        return -1;
    }

    /* 解析复杂 json 数据 */
    cout << "解析 json 数组" << endl;
    if (parse_array() != 0) {
        cout << "parse array failed" << endl;
    }

    return 0;
}

5. libcurl 解析

• libcurl 是一个跨平台的网络协议库，支持 http、https，ftp，telnet 等应用层协议
• libcurl 主要功能就是用不同的协议连接和沟通不同的服务器

5.1 libcurl 编译

• 流程同 CEF 编译
  • 参考链接

5.2 使用 libcurl 进行 http post 请求

#include 
#include "curl/curl.h"
#include 
#include 
#include 
#include "json.hpp"

using namespace std;

using json_t = nlohmann::json;

// 数据处理回调函数
size_t write_data(void* ptr, size_t size, size_t nmemb, void* stream) {
    string data((const char*)ptr, (size_t)size * nmemb);
    *((stringstream*)stream) << data << endl;
    return size * nmemb;
}

int main() {
    /* 以下代码为通过 Postman 生成 */
    // Postman 是一款用于发送 HTTP 请求的测试工具
    CURL* curl;
    CURLcode res;
    stringstream jsonRespon;

    curl = curl_easy_init();
    if (curl) {
        curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "POST");
        curl_easy_setopt(curl, CURLOPT_URL, "127.0.0.1:8080/login");
        curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);
        //curl_easy_setopt(curl, CURLOPT_DEFAULT_PROTOCOL, "https");
        struct curl_slist* headers = NULL;
        headers = curl_slist_append(headers, "Content-Type: application/json");
        curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
        
        string data = R"(
            {
                "username":"jackhui",
                "password":"1234"
            }
        )";

        curl_easy_setopt(curl, CURLOPT_POSTFIELDS, data.c_str());
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, &jsonRespon);

        res = curl_easy_perform(curl);
        if (res != 0) {
            cout << "request failed" << endl;
            return -1;
        }
    }
    curl_easy_cleanup(curl);
    cout << "request success 222" << endl;
    /* 以上代码为通过 Postman 生成 */

    string json = jsonRespon.str();

    try {
        json_t j = json_t::parse(json);
        cout << j.dump(4) << endl;

        string data = j["date"];
    } catch (std::exception& e) {
        cout << "json parse failed" << endl;
        return -2;
    }

    return 0;
}

6. websocket

6.1 基本概念

• websocket 是 HTML5 中新增的一个协议，这个协议的出现，让客户端和服务器之前的数据交互变成全双工的

• websocket 的出现，最主要的变化是允许服务器主动给客户端推送数据。这一大改变，就让 websocket 具有了以往其它协议无法比拟的实时通信能力。要实现 websocket 服务，需要客户端和服务端都得支持 websocket 协议才可以

• websocket 详解

• Websocket 能做什么？

  • 聊天、消息推送、多人在线业务
  • 推荐一个开源项目 OpenIM

• websocket 与 http 的区别

  • 相同点
    • 都是一样基于 TCP 的，都是可靠性传输协议
    • 都是应用层协议
  • 不同点
    • websocket 是持久连接，http 是短连接
    • websocket 的协议是以 ws/wss 开头，http 对应的是 http/https
    • websocket 是有状态的，http 是无状态的
    • websocket 连接之后服务器和客户端可以双向发送数据，http 只能是客户端发起一次请求之后，服务器才能返回数据
    • websocket 连接建立之后，不需要再发送 request 请求，数据直接从 TCP 通道传输

• websocketpp 是用 c++ 实现的一个 websocket 库，用来支持 websocket 协议

  • websocketpp

6.2 C++ Qt 实现 websocket server

Qt websocket 的实现（需包含 websockets 第三方模块）

• QWebSocketServer（服务端）
• QWebSocket（客户端）

• WebsocketServer.h

#pragma once

#include 
#include "ui_WebsocketServer.h"
#include 
#include 
#include 

class WebsocketServerDemo : public QWidget {
    Q_OBJECT

public:
    WebsocketServerDemo(QWidget *parent = Q_NULLPTR);
    ~WebsocketServerDemo();

private slots:
    void on_btnOpenServer_clicked();
    void on_btnCloseServer_clicked();
    void on_btnSend_clicked();

    void onNewConnection();
    void processTextMessage(QString message);
    void socketDisconnected();

private:
    Ui::WebsocketServerClass ui;

    QWebSocketServer* m_WebSocketServer = nullptr;

    QList<QWebSocket*> m_clients;
    bool m_debug;
    QWebSocket* pSocket;
    QDateTime* current_date_time;
    QMap<QString, QWebSocket*> mapSocket;
};

• WebsocketServer.cpp

#include "WebsocketServer.h"
#include 
#include 
#include 
#include 

using namespace std;

WebsocketServerDemo::WebsocketServerDemo(QWidget *parent) : QWidget(parent) {
    ui.setupUi(this);
   
    this->setWindowTitle(u8"Websocket Server");
    this->resize(1000, 600);

    ui.lineEdit_IP->setText("192.168.74.1");
    ui.lineEdit_Port->setText("8000");

    // 创建服务
    m_WebSocketServer = new QWebSocketServer(u8"server", QWebSocketServer::NonSecureMode);
}

WebsocketServerDemo::~WebsocketServerDemo() {
    if (m_WebSocketServer) {
        if(m_WebSocketServer->isListening())
            m_WebSocketServer->close();
    }  
}

// 开启服务
void WebsocketServerDemo::on_btnOpenServer_clicked() {
    QString ip = ui.lineEdit_IP->text();
    QString port = ui.lineEdit_Port->text();

    // 监听 ip 和端口
    if (m_WebSocketServer->listen(QHostAddress(ip), port.toInt())) {
        ui.textEdit_RecvMsg->append(u8"服务开启成功");
        ui.btnOpenServer->setEnabled(false);
        // 服务成功开启则触发 onNewConnection() 槽函数
        connect(m_WebSocketServer, SIGNAL(newConnection()), this, SLOT(onNewConnection()));
    } else {
        QMessageBox::information(this, u8"提示", u8"监听失败, 是否开启了代理，或者IP错误");
    }
}

// 关闭服务
void WebsocketServerDemo::on_btnCloseServer_clicked() {
    if (m_WebSocketServer) {
        if (m_WebSocketServer->isListening()) {
            m_WebSocketServer->close();
            ui.btnOpenServer->setEnabled(true);
            ui.textEdit_RecvMsg->append(u8"服务关闭");
        }
    }
}

// 处理新的客户端连接
void WebsocketServerDemo::onNewConnection() {
    pSocket = m_WebSocketServer->nextPendingConnection();
    m_clients << pSocket;

    // 处理接到消息的信号
    connect(pSocket, SIGNAL(textMessageReceived(QString)), this, SLOT(processTextMessage(QString)));
    // 处理断线的信号
    connect(pSocket, SIGNAL(disconnected()), this, SLOT(socketDisconnected()));

    QString peerName = pSocket->requestUrl().toString();
    cout << "peerName = " << peerName.toStdString() << endl;

    // 将 ip 和 socket 保存到 map
    mapSocket[peerName] = pSocket;

    ui.listWidget_OnlineUser->addItem(peerName);
}

// 处理接收到的消息
void WebsocketServerDemo::processTextMessage(QString message) {
    QString time = current_date_time->currentDateTime().toString("yyyy.MM.dd hh:mm:ss.zzz ddd");
    QString item = pSocket->requestUrl().toString();
    ui.textEdit_RecvMsg->append(time + "" + item + "\n" + message);

    // 处理消息转发
    //...
}

// 客户端连接断开的操作
void WebsocketServerDemo::socketDisconnected() {
    for (auto sk : m_clients) {
        if (!sk->isValid()) {
            QString temp_key;
            ui.textEdit_RecvMsg->append("map size = " + QString(mapSocket.size()) + "\n");
            for (auto it = mapSocket.begin(); it!=mapSocket.end(); it++) {
                if (it.value() == sk) {
                    // 删除项
                    QList<QListWidgetItem*> list;
                    list = ui.listWidget_OnlineUser-> findItems(it.key(), Qt::MatchCaseSensitive);

                    QListWidgetItem* sel = list[0];
                    int r = ui.listWidget_OnlineUser->row(sel);

                    QListWidgetItem* item = ui.listWidget_OnlineUser->takeItem(r);
                    ui.listWidget_OnlineUser->removeItemWidget(item);

                    delete item;
                    m_clients.removeOne(sk);

                    QString time = current_date_time->currentDateTime().toString("yyyy.MM.dd hh:mm:ss.zzz ddd");
                    ui.textEdit_RecvMsg->append(time + "" + it.key() + "下线了\n");

                    temp_key = it.key();
                }
            }

            mapSocket.remove(temp_key);
            ui.textEdit_RecvMsg->append("after remove, map size = " + QString(mapSocket.size()) + "\n");
        }
    }
}

// 群发消息
void WebsocketServerDemo::on_btnSend_clicked() {
    QString msg = ui.textEdit_send->document()->toPlainText();

    for (auto sk : m_clients) {
        sk->sendTextMessage(msg);
    }
}

6.3 C++ Qt 实现 websocket client

• WebSocketClientDemo.h

#pragma once

#include 
#include "ui_WebSocketClientDemo.h"
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

class WebSocketClientDemo : public QWidget {
    Q_OBJECT

public:
    WebSocketClientDemo(QWidget *parent = Q_NULLPTR);
    ~WebSocketClientDemo();

private slots:
    void on_btnConnect_clicked();
    void on_btnDisconnect_clicked();
    void on_btnSend_clicked();

    void onconnected();
    void onTextMessageReceived(const QString& message);
    void closeConnection();    

private:
    Ui::WebSocketClientDemoClass ui;

    QUrl m_url;
    QWebSocket m_websocket;
    bool m_debug;
    QDateTime* current_date_time;
};

• WebSocketClientDemo.cpp

#include "WebSocketClientDemo.h"
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

using namespace std;

WebSocketClientDemo::WebSocketClientDemo(QWidget *parent) : QWidget(parent) {
    ui.setupUi(this);

    ui.lineEdit_URL->setText("ws://192.168.74.1:8000/topic=10001");
    ui.label_ConnectStatus->clear();

    connect(&m_websocket, SIGNAL(connected()), this, SLOT(onconnected()));
    connect(&m_websocket, SIGNAL(disconnected()), this, SLOT(closeConnection()));
    connect(&m_websocket, SIGNAL(textMessageReceived(QString)), this, SLOT(onTextMessageReceived(QString)));
}

WebSocketClientDemo::~WebSocketClientDemo() {
    m_websocket.errorString();
    m_websocket.close();
}

// 断开连接操作
void WebSocketClientDemo::closeConnection()  {   
    ui.label_ConnectStatus->setText("disconnected");
}

// 连接服务器
void WebSocketClientDemo::on_btnConnect_clicked() {
    QString _text = ui.lineEdit_URL->text();
    QUrl url = QUrl(_text);
    m_websocket.open(url);
}

// 连接上之后
void WebSocketClientDemo::onconnected() {
    ui.label_ConnectStatus->setText(tr("connected"));
    ui.btnConnect->setEnabled(false);
    ui.btnDisconnect->setEnabled(true);
}

// 收到消息
void WebSocketClientDemo::onTextMessageReceived(const QString& message) {
    QString time = current_date_time->currentDateTime().toString("yyyy.MM.dd hh:mm:ss.zzz ddd");
    ui.textEdit_recv->setText(time + "\n" + message);
}

// 断开
void WebSocketClientDemo::on_btnDisconnect_clicked() {
    m_websocket.close();
}

// 发送消息
void WebSocketClientDemo::on_btnSend_clicked() {
    QString msg = ui.textEdit_send->document()->toPlainText();

    string dataMsg = R"(
        "sender":"10002",
        "receiver":"10001",
        "msg":"你好"
    )";
    
    m_websocket.sendTextMessage(msg);
}