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todo: Add link(s) here to tutorials and example code. For example, at the moment I'm looking for a better example of reading a tar file, and extracting and expanding gzip files inside that tar file (than the approach I came up with ExtractAndDecompressGzipFiles).

VfsCookbook - a cookbook has been started

How

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can I enter ftp passive mode?

FileSystemOptions opts = new FileSystemOptions();
FtpFileSystemConfigBuilder.getInstance().setPassiveMode(opts, true);
FileObject fo = VFS.getManager().resolveFile("ftp://host/path_to/file.txt", opts);

How

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do I use the org.apache.commons.vfs.FileSelector or org.apache.commons.vfs.FileFilter?

The FileFilter can be used to mimic the java.io.FileFilter interface.

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FileSelector ff = new FileSelector()
{
    public boolean includeFile(FileSelectInfo fileInfo) throws Exception
    {
        FileObject fo = fileInfo.getFile();
        return fo.getName().getBaseName().startsWith("ABC-");
    }

    public boolean traverseDescendents(FileSelectInfo fileInfo) throws Exception
    {
        return true;
    }   		
};
VFS.getManager().resolveFile("/base/folder").findFiles(ff);

How do I keep an SFTP connection from hanging?

If your program is transferring files, but not exiting afterward, this is actually an issue with properly closing down the connection when you are done. If you acquired a FileSystemManager with

private FileSystemManager fsManager = VFS.getManager();

the getManager() method probably returned a StandardFileSystemManager which extends the DefaultFileSystemManager class and implements the FileSystemManager interface.

What you are probably after is the close() method of the DefaultFileSystemManager to clean up any temporary files and close all providers. Cast the FileSystemManager to a DefaultFileSystemManager access the close() method like this:

((DefaultFileSystemManager) fsManager).close();

How can I connect to an SFTP server even if there is no entry in known_hosts?

JSch, the library that provides VFS with SFTP functionality, checks that the host one tries connecting to is a known host, i.e. has an entry in the file $HOME/.ssh/known_hosts. By default, connections to unkown hosts are rejected by throwing an exception. You can change this behaviour by specifying the strict host key checking option:

FileSystemOptions opts = new FileSystemOptions();
SftpFileSystemConfigBuilder.getInstance().setStrictHostKeyChecking(opts, "no");
FileSystemManager fsManager = VFS.getManager();
FileObject foo = fsManager.resolveFile("sftp://login:password@host/foo.bar", opts);

// Do some stuff

foo.close();
((DefaultFileSystemManager) fsManager).close();