Some potential solutions:
1) Set up Apache in front of JBoss and let your static content live under the document root
2) Write a bean that is capable of accessing the files based on a configurable property. Configure the bean in Spring. Write a servlet that uses the bean to get the content and writes it directly to the response OutputStream.
3) Write a servlet that does the above without using Spring.
4) Set up Apache behind JBoss; write a servlet to get the static files from the Apache server as in 2) and 3). This allows you to have multiple JBoss servers without duplicating the content files.
5) Put the content files in a directory named static.war and deploy it as an exploded war. May or may not give you the necessary modification mechanics.