Retrieve all sub folders contents using Java Apache Commons Net library

Question

Using the Java Apache Commons Net FTPClient, is it possible to make a listFiles call that will retrieve the contents of a directory plus all its sub directories as well?

Answer 1

The library cannot do it on its own. But you can implement it using a simple recursion:

private static void listFolder(FTPClient ftpClient, String remotePath)
    throws IOException
{
    System.out.println("Listing folder " + remotePath);
    FTPFile[] remoteFiles = ftpClient.listFiles(remotePath);
    for (FTPFile remoteFile : remoteFiles)
    {
        if (!remoteFile.getName().equals(".") && !remoteFile.getName().equals(".."))
        {
            String remoteFilePath = remotePath + "/" + remoteFile.getName();

            if (remoteFile.isDirectory())
            {
                listFolder(ftpClient, remoteFilePath);
            }
            else
            {
                System.out.println("Found file " + remoteFilePath);
            }
        }
    }
}

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Not only that the Apache Commons Net library cannot do this in one call. There's actually no API in FTP for that. Though some FTP servers have proprietary non-standard ways. For example ProFTPD has -R switch to LIST command (and its companions).

FTPFile[] remoteFiles = ftpClient.listFiles("-R " + remotePath);

See also a related C# question:
Getting all FTP directory/file listings recursively in one call

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You can also consider running du -sh * . via SSH from Java.