Is there an easy way to map a directory in the web.xml or other deployment descriptor (jetty.xml, etc) files?

For example, if I have a directory /opt/files/ is there a way that I can access its files and sub-directories by visiting http://localhost/some-mapping/? It strikes me that there should be some simple way of doing this, but I haven't been able to find out how (via google, stackoverflow, etc). All I've found are servlets that mimic fileservers, which is not what I would like.

For reference I am using jetty on an AIX box.