public abstract class FileSystemLayer
A file system layer is a layer between a VirtualFile and the real file
system. This allows for non-traditional file systems to be transparently added
to the VFS system. These layers are specified by symlinks in the VFS, which
use a specific URI to denote the path. Once a FSL is implemented,
it is trivial for a user to add a new symlink to make use of the new FSL.
All functions may throw an IOException, which is not something real File objects
normally do (for instance, delete() will simply return false) but to give the user
more information, this class throws exceptions instead.