向服务器请求数据,Post是一种常见的方法,使用Post需要三种元素:URL,Header,Body。
Qt中使用QNetworkAccessManager来提供Post,一共三种接口,如下所示:
QNetworkReply *QNetworkAccessManager::post(const QNetworkRequest &request, QIODevice *data);
QNetworkReply *QNetworkAccessManager::post(const QNetworkRequest &request, const QByteArray &data);
QNetworkReply *QNetworkAccessManager::post(const QNetworkRequest &request, QHttpMultiPart *multiPart);
Qt之Post与字节流一文中介绍了第二种接口,但是这种接口很是麻烦,缺乏抽象性。
本篇文章介绍第三种接口,该接口用到了QHttpMultiPart与QHttpPart两个类。
QHttpPart用于表示一个消息体,该消息体需要设置Header和Body两个部分,一个消息体的结构如下所示:
//Header
Content-Type: text/plain
Content-Disposition: form-data; name="text"
//Body
here goes the body
这两个部分在QHttpPart中的具体设置方法如下:
QHttpPart textPart;
textPart.setHeader(QNetworkRequest::ContentTypeHeader, QVariant("text/plain"));
textPart.setHeader(QNetworkRequest::ContentDispositionHeader, QVariant("form-data; name=\"text\""));
textPart.setBody("here goes the body");
上面是QHttpPart的使用方法,但是这样设置出来之后呢?下面要做的是将QHttpPart添加到QHttpMultiPart,添加方法如下:
QHttpMultiPart *multiPart = new QHttpMultiPart(QHttpMultiPart::FormDataType);
QHttpPart textPart;
textPart.setHeader(QNetworkRequest::ContentTypeHeader, QVariant("text/plain"));
textPart.setHeader(QNetworkRequest::ContentDispositionHeader, QVariant("form-data; name=\"text\""));
textPart.setBody("here goes the body");
multiPart->append(textPart);
现在一个完整的QHttpMultiPart就构建完成了,可以使用如下方法发送http消息:
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
下面给出完整的http消息发送流程:
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.
[1] Qt助手