I'm submitting a series of patches to the ext2/3/4 dump utility and noticed that the commons-compress library doesn't have an archiver for it. It's as old as tar and fills a similar niche but the later has become much more widely used. Dump includes support for sparse files, extended attributes, mac os finder, SELinux labels (I think), and more. Incremental dumps can capture that files have been deleted.
I should have initial support for a decoder this weekend. I can read the directory entries and inode information (file permissions, etc.) but need a bit more work on extracting the content as an InputStream.