It sounds like you are looking for a Servlet Filter class.
It looks like this:
Then in your web.xml you have this code:
Now every single request on your site will first have to go through the filter. What what? can it be that simple? YES :)
Now in your filter you just have to read through the XML file and then pass it in a session or just the request to the JSP that can then display it
This also ensures that the user wont be able to get to the JSP if there is an error in your XML file which could lead to a complete crash of the page.
I use a filter to get all the data for all my JSP pages and also creating sessions and objects needed for the JSP pages.
Then the JSP pages ONLY job is to display data :)
subject: Need to show dynamic field in JSP (read from xml file)