【Qt】使用Qt发送http请求封装一个通用类

需求

Qt 代码中使用QNetworkRequest、QNetworkReply进行http请求，能不能整理成一个通用的方法或者类。

实现

HttpClient类

#include <QObject>  
#include <QNetworkAccessManager>  
#include <QNetworkRequest>  
#include <QNetworkReply>  
#include <QUrl>  
#include <QUrlQuery>  
#include <QByteArray>  
#include <QJsonObject>  
#include <QJsonDocument>  
#include <QDebug>  
#include <QEventLoop>
  
class HttpClient : public QObject  
{  
    Q_OBJECT  
  
public:  
    explicit HttpClient(QObject *parent = nullptr)  
        : QObject(parent), networkManager(new QNetworkAccessManager(this))  
    {  
        connect(networkManager, &QNetworkAccessManager::finished, this, &HttpClient::onReplyFinished);  
    }  
  
    void get(const QUrl &url, const QUrlQuery &query = QUrlQuery())  
    {  
        QUrl fullUrl = url;  
        fullUrl.setQuery(query);  
        QNetworkRequest request(fullUrl);  
        networkManager->get(request);  
        eventLoot->exec();
    }  
  
    void post(const QUrl &url, const QByteArray &data)  
    {  
        QNetworkRequest request(url);  
        request.setHeader(QNetworkRequest::ContentTypeHeader, "application/json");  
        networkManager->post(request, data); 
        eventLoot->exec(); 
    }  
  
signals:  
    void requestFinished(const QByteArray &responseData, QNetworkReply::NetworkError error);  
  
private slots:  
    void onReplyFinished(QNetworkReply *reply)  
    {  
        if (reply->error() == QNetworkReply::NoError) {  
            QByteArray responseData = reply->readAll();  
            emit requestFinished(responseData, QNetworkReply::NoError);  
        } else {  
            emit requestFinished(QByteArray(), reply->error());  
        }  
        reply->deleteLater();  
    }  
  
private:  
    QNetworkAccessManager *networkManager;  
    QEventLoop eventLoop;
};

HttpClient中使用了一个QEventLoop，为了使发送的事件得到及时的处理，不加这个的话，测试发现半天都不能调到onReplyFinished槽函数中。

使用

#include <QCoreApplication>  
#include <QUrl>  
#include <QUrlQuery>  
#include <QJsonDocument>  
#include <QJsonObject>  
#include <QByteArray>  
#include "HttpClient.h"  
  
int main(int argc, char *argv[])  
{  
    QCoreApplication a(argc, argv);  
  
    HttpClient client;  
  
    // 发送GET请求  
    QUrl getUrl("https://jsonplaceholder.typicode.com/posts/1");  
    QObject::connect(&client, &HttpClient::requestFinished, [](const QByteArray &responseData, QNetworkReply::NetworkError error) {  
        if (error == QNetworkReply::NoError) {  
            QJsonDocument jsonDoc = QJsonDocument::fromJson(responseData);  
            QJsonObject jsonObj = jsonDoc.object();  
            qDebug() << "GET Response:" << jsonObj;  
        } else {  
            qDebug() << "GET Error:" << error;  
        }  
    });  
    client.get(getUrl);  
  
    // 发送POST请求  
    QUrl postUrl("https://jsonplaceholder.typicode.com/posts");  
    QJsonObject postData;  
    postData["title"] = "foo";  
    postData["body"] = "bar";  
    postData["userId"] = 1;  
    QByteArray postDataBytes = QJsonDocument(postData).toJson();  
  
    QObject::connect(&client, &HttpClient::requestFinished, [](const QByteArray &responseData, QNetworkReply::NetworkError error) {  
        if (error == QNetworkReply::NoError) {  
            QJsonDocument jsonDoc = QJsonDocument::fromJson(responseData);  
            QJsonObject jsonObj = jsonDoc.object();  
            qDebug() << "POST Response:" << jsonObj;  
        } else {  
            qDebug() << "POST Error:" << error;  
        }  
    });  
    client.post(postUrl, postDataBytes);  
  
    return a.exec();  
}

优化

上述代码可能存在的问题，如果有嵌套http请求，可能会造成请求递归调用，最终导致栈溢出。

修改点在于，连接信号槽的时候，使用发送请求时返回的QNetworkReply去连接对应处理的槽函数。

#include <QObject>  
#include <QNetworkAccessManager>  
#include <QNetworkRequest>  
#include <QNetworkReply>  
#include <QUrl>  
#include <QUrlQuery>  
#include <QByteArray>  
#include <QJsonObject>  
#include <QJsonDocument>  
#include <QDebug>  
#include <QEventLoop>
  
class HttpClient : public QObject  
{  
    Q_OBJECT  
  
public:  
    explicit HttpClient(QObject *parent = nullptr)  
        : QObject(parent), networkManager(new QNetworkAccessManager(this))  
    {  
        //connect(networkManager, &QNetworkAccessManager::finished, this, &HttpClient::onReplyFinished);  
    }  
  
    void get(const QUrl &url, const QUrlQuery &query = QUrlQuery())  
    {  
        QUrl fullUrl = url;  
        fullUrl.setQuery(query);  
        QNetworkRequest request(fullUrl);  
        QNetworkReply *reply = networkManager->get(request);  
         //这里进行连接
        connect(reply, SIGNAL(finished()), &eventLoop, SLOT(quit()));
	    connect(reply, &QNetworkReply::finished, this, [this, reply]()
		{
			onReplyFinished(reply);
		});
        eventLoot->exec();
    }  
  
    void post(const QUrl &url, const QByteArray &data)  
    {  
        QNetworkRequest request(url);  
        request.setHeader(QNetworkRequest::ContentTypeHeader, "application/json");  
        QNetworkReply *reply = networkManager->post(request, data);
        //这里进行连接
        connect(reply, SIGNAL(finished()), &eventLoop, SLOT(quit()));
	    connect(reply, &QNetworkReply::finished, this, [this, reply]()
		{
			onReplyFinished(reply);
		}); 
        eventLoot->exec(); 
    }  
  
signals:  
    void requestFinished(const QByteArray &responseData, QNetworkReply::NetworkError error);  
  
private slots:  
    void onReplyFinished(QNetworkReply *reply)  
    {  
        if (reply->error() == QNetworkReply::NoError) {  
            QByteArray responseData = reply->readAll();  
            emit requestFinished(responseData, QNetworkReply::NoError);  
        } else {  
            emit requestFinished(QByteArray(), reply->error());  
        }  
        reply->deleteLater();  
    }  
  
private:  
    QNetworkAccessManager *networkManager;  
    QEventLoop eventLoop;
};