The key word in the problem statement is "linked"--I put symbolic links under the static exploded war file directory to the files. I tried removing the links and creating the hierarchy and files in place under the exploded war file, and http resolution worked fine. So to the best of my belief, the web server (Catalina?) is simply not able to resolve symbolic links, it needs the actual files to be in the exploded war. Which is a little limiting, actually, if you have a huge file structure and you want to store it on a separate mount.
Any comments from anyone in the know about this limitation of Catalina?
you can enable the symbol link support by adding allowLinking="true" in the context.xml of your web app.