If so how do you do this?
(jboss/tomact embedded/jdk 1.5)
not embedded js/css but an actual file...
Sure, JSP can output any necessary text you need be that (X)HTML or CSS or JavaScript code. I do this regularly for ERP customization, inject a javascript script at the end of every page and via the context in which it loads able to manipulate necessary data fields on the page without touching the underlying app.