1.首先调用函数

void UBApplication::postHttpRequest()
{
    QNetworkRequest request;
    QNetworkAccessManager* naManager = new QNetworkAccessManager(this);
     QObject::connect(naManager, SIGNAL(finished(QNetworkReply*)), this, SLOT(requestFinished(QNetworkReply*)));

    request.setHeader(QNetworkRequest::ContentTypeHeader,QVariant("application/json"));
    request.setUrl(QUrl("http://119.3.131.228:9001/logincontroller/login"));

    QJsonObject obj1;
    obj1.insert("password",loginPwd);
    obj1.insert("username", loginName);

    QByteArray byte_array = QJsonDocument(obj1).toJson();
    qDebug()<< "user  info " << obj1;
    QNetworkReply* reply = naManager->post(request,byte_array);
}

2.完成时候调用槽函数

void UBApplication::requestFinished(QNetworkReply* reply)
{
    QByteArray bytes = reply->readAll();
    // 获取http状态码
    QVariant statusCode = reply->attribute(QNetworkRequest::HttpStatusCodeAttribute);
    if(statusCode.isValid())
    {
          qDebug() << "status code=" << statusCode.toInt();
    }

    QNetworkReply::NetworkError err = reply->error();
    if(err != QNetworkReply::NoError)
    {
        qDebug() << "Failed: " << reply->errorString();
    }
    else
    {
        // 获取返回内容
        qDebug() << "loginResultJson  is  " <<  QString::fromStdString(bytes.toStdString());
        loginResultJson =  QString::fromStdString(bytes.toStdString());
        //处理返回数据
    }
}

3.需要注意的是，编码格式。