Java – Monitoring progress using Apache Commons FTPClient

apache-commonsdownloadftpftp-clientjava

I have a simple FTPClient class that downloads files form an FTP server. I also need to monitor progress of the download, but I do not see a way how. The actually download files function is a simple function of

(your ftp client name).retrieveFile(arg1,arg2);

How can I monitor the download progress?

Thanks,
Anon.

Best Answer

You need a CountingOutputStream (as seen on Commons IO: http://commons.apache.org/io/api-release/index.html). You create one of those, wrap your destination OutputStream in it, and then you can check the ByteCount on demand to monitor the download progress..

EDIT: You'd do something like this:

int size;
String remote, local;

// do some work to initialize size, remote and local file path
// before saving remoteSource to local
OutputStream output = new FileOutputStream(local);
CountingOutputStream cos = new CountingOutputStream(output){
    protected void beforeWrite(int n){
        super.beforeWrite(n);

        System.err.println("Downloaded "+getCount() + "/" + size);
    }
};
ftp.retrieveFile(remote, cos);

output.close();

If your program is multithreaded you might want to monitor the progress using a separate thread (for example, for a GUI program), but that's all application-specific detail.

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