You might be interested in this project:
https://weblets.dev.java.net/
I use it in a JSF project and it works nicely:
(a) solving the stale-resource problem when new releases are made
(for js, png, css, etc);
(b) allowing resources to be served from the private WEB-INF dir,
or directly from a jarfile;
(c) allowing the base address for resources encoded in jsp pages to
be "virtual", so that moving the resource does not mean changing
all the pages.
I don't know how useful (b) and (c) are for jspwiki, but solving
(a) is nice at least.
Actually, b) would be very useful as well, since security-wise it
would make sense to put stuff inside the WEB-INF directory, so
resources can't be accidentally exposed.
Andrew, want to take a look at this?
/Janne