<%@ taglib uri="http://java.sun.com/jsptl/ea/jx" prefix="jx" %>
<jx:set var="url"> 
  <jx:expr value="$param:url"
           default="http://java.sun.com/products/jsp/"/>
</jx:set>
<jx:declare id="url" type="java.lang.String"/>
<% response.sendRedirect(url); %>