C++ Qt QFileSystemWatcher 文件上传双

Question

我遇到文件被两次上传到服务器的问题。

我在 Windows XP 上使用 C++ Qt 的 QFileSystemWatcher 类在文件夹更改时发送文件文件很小 (1-12kb)。

应用程序通过在文件夹发生变化时扫描文件夹来发送文件(在 directoryChanged 信号上)，遍历文件并发送我需要的文件。服务器响应一个 xml 文件，该文件返回到同一文件夹中供另一个应用程序处理它。

显然发生的事情是在某些系统上几乎同时有 2 个非常快的 directoryChanged 信号，并且发生了两个非常快的文件上传。

服务器正在运行 Apache 和 PHP，并且在 PHP 端有一个简单的 MUTEX，但我只是想找到似乎在 Qt 端的问题的根源。我愿意使用另一个类、另一个库或直接使用 C++。

这是一些代码，我去掉了所有不相关的内容:

this->w = new QFileSystemWatcher();
this->w->addPath("C:/POSERA/MaitreD/DATA/INT");

QStringList directoryList = w->directories();
Q_FOREACH(QString directory, directoryList)
{
    qDebug() << "Watching Main Directory name: " << directory << endl;
}

DirectoryWatcher* dw = new DirectoryWatcher;

QObject::connect( this->w, SIGNAL(directoryChanged(const QString&)),
                  dw, SLOT(directoryChanged(const QString&)));

和 DirectoryWatcher.cpp:

DirectoryWatcher::DirectoryWatcher(QWidget* parent) : QWidget(parent)
{
    lockSend = false;
}

void DirectoryWatcher::directoryChanged(const QString& str)
{
    directoryLastChanged = str;

    QByteArray byteArray = str.toUtf8();
    const char* cString = byteArray.constData();

    sendChangedFiles(cString);
}

void DirectoryWatcher::sendChangedFiles(const char* path)
{
    DIR *dir;
    struct dirent *ent;
    if ((dir = opendir (path)) != NULL)
    {
        QString str;

        while ((ent = readdir (dir)) != NULL)
        {
            str = QString("%1/%2").arg(path, ent->d_name);

            QFileInfo info(str);

            if (lockSend == false &&
               (info.completeSuffix() == "xml" || info.completeSuffix() == "XML") &&
               (info.baseName() != "") &&
               (!info.baseName().startsWith("REDM")) &&
               (!info.baseName().startsWith("REFT")))
            {
                // reset the counter.
                this->resendCounter = 0;

                sendFileAndAccept(str.toUtf8().constData());
            }
        }
        closedir (dir);
    }
    else
    {
        qDebug() << "Could not open directory" << endl;
    }
}

class QNetworkRequest;
class QNetworkReply;

void DirectoryWatcher::sendFileAndAccept(const char* path)
{
    // increment the resend counter
    this->resendCounter++;

    QFileInfo fileInfo(path);

    QNetworkAccessManager * mgr = new QNetworkAccessManager(this);
    connect(mgr,SIGNAL(finished(QNetworkReply*)),
            this,SLOT(saveResponse(QNetworkReply*)));
    connect(mgr,SIGNAL(finished(QNetworkReply*)),
            mgr,SLOT(deleteLater())); // @todo delete later

    QHttpMultiPart *multiPart = new QHttpMultiPart(QHttpMultiPart::FormDataType);

    QHttpPart filePart;
    filePart.setHeader(QNetworkRequest::ContentTypeHeader, QVariant("text/xml")); // @todo test
    filePart.setHeader(QNetworkRequest::ContentDispositionHeader, QVariant("form-data; name=\"someFile\"; filename=\"" + fileInfo.baseName() + ".xml\""));

    currentFileSent = fileInfo.baseName();

    QFile *file = new QFile(path);
    file->open(QIODevice::ReadOnly);
    filePart.setBodyDevice(file);
    file->setParent(multiPart); // we cannot delete the file now, so delete it with the multiPart

    multiPart->append(filePart);

    // POST request
    QNetworkReply *reply = mgr->post(QNetworkRequest(QUrl(XXXXXX)), multiPart);

    multiPart->setParent(reply); // delete the multiPart with the reply

    // lock
    lockSend = true;
}

void DirectoryWatcher::saveResponse(QNetworkReply *rep) {

    // get the response
    QByteArray bts = rep->readAll();
    QString str(bts);

    // compute new path
    QString partName = currentFileSent.mid(1, currentFileSent.length());
    QString newPath = QString("%1/A%2.xml").arg(directoryLastChanged, partName);

    qDebug() << "new path: " << newPath << endl;

    switch (rep->error()) {
        case QNetworkReply::NoError: {
            qDebug() << "NO ERROR" << endl;

            // save response to a file.

            QFile file(newPath);
            file.open(QIODevice::WriteOnly | QIODevice::Text);
            QTextStream out(&file);
            out << str;

            file.close();

            break;
        }
        default:

//        case QNetworkReply::TimeoutError :
//        case QNetworkReply::HostNotFoundError :
            qDebug() << "NETWORK REPLY ERROR" << endl;
            // resend the file if the counter is < 10
            if (this->resendCounter < 5) {

                // delay by n sec
                QTime dieTime = QTime::currentTime().addSecs(1);
                while( QTime::currentTime() < dieTime )
                    QCoreApplication::processEvents(QEventLoop::AllEvents, 100);

                sendFileAndAccept(this->lastPathSent.toStdString().c_str());
            } else {

                // after 10 attempts, we're probably sure that the network is down
                // save the file somewhere and generate a default one to prevent timeouts.

                qDebug() << "Saving file for later..." << endl;
                if (!saveFileForLater(lastPathSent.toStdString().c_str())) {
                    qDebug() << "ERROR SAVING FILE, CHECK IF FOLDER EXISTS AND THE PERMISSIONS." << endl;
                }

                // generate a default one to prevent timeouts.
                qDebug() << "Generate a default file..." << endl;
                // ...
            }

            break;
    }

    // unlock
    lockSend = false;

    rep->deleteLater(); // prevent memory leak
}

bool DirectoryWatcher::saveFileForLater(const char* pathToRequestFile) {

    QFile file(pathToRequestFile);
    if (!file.open(QIODevice::ReadOnly | QIODevice::Text)) {
        qDebug() << "readonly and text" << endl;
        return false;
    }

    QString path(pathToRequestFile);
    QFileInfo fileinfo(path);

    QString newPath = "C:\\data\\offline\\" + fileinfo.fileName();

    return file.copy(newPath);

}

感谢您的帮助。

Answer 1

directoryChanged 发出 2 次最可能的原因是普通编辑器在保存更改时会删除文件的新版本并将其写入磁盘。这就是为什么在删除文件时有一个信号，在重新创建文件时有一个信号的原因。