Dynamically setting the contentType in Struts.

[Tim Eyre]

Does anyone know how I dynamically set the contentType of a page? I want to give my users the option of seeing their results as an excel spreadsheet, or in HTML format. Effectively I want to do:

<% if (session.getAttribute("format").equals("Excel")) { %>
   <%@ page contentType="application/vnd.ms-excel" %>
<% } %>

But this will always run the report in Excel. I'm sure I need to set the contentType first and then dispatch the request, but am unsure how to do this in Struts.
Any ideas?
Thanks
Tim