I don't know about doing this in JSP. But it's easily done in a Java servlet, with code such as:
Enumeration p = req.getParameterNames();
while (p.hasMoreElements()) {
String name = (String)p.nextElement();
String value = req.getParameter(name);
transformer.setParameter(name, value);
}
See SaxonServlet.java in the samples directory of the Saxon distribution for a more complete example.
Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference