An appropriate use for PortletRequestWrapper?

[Mark McLaren <ma...@gmail.com>]

I was answering a query on the uPortal mailing list.  It was
concerning how to access portlet variables using a tag library, JSTL
being the obvious choice for this.

What follows is my response to the original query; does it make sense?
 Is this what PortletRequestWrapper is for?  How else would you access
variables in portlet request scope etc. without resorting to
scriptlets?

The <portlet:defineObjects/> from the portlet taglib will create
renderRequest, renderResponse and portletConfig objects in the request
and page scopes for use in your JSP.  You should be able to access
these objects using JSTL.  Therefore something like this should work:

<%@ taglib uri="http://java.sun.com/jstl/core" prefix="c" %>
<%@ taglib uri="http://java.sun.com/portlet" prefix="portlet"%>
<portlet:defineObjects/>

ServerName : <c:out value="${renderRequest.serverName}"/><br />
ServerPort : <c:out value="${renderRequest.serverPort}"/><br />

This only takes you so far, I'm not sure you can access portlet scoped
attributes this way.  As I understand it, in JSTL application
variables such as the various scopes are mapped to implicit objects so
that javax.servlet.http.HttpServletRequest is mapped to
org.apache.taglibs.standard.lang.jstl.ImplicitObjects.  In JSTL this
enables easy access to standard HTTP scoped variables without
scriptlets.  As far as I know there is no such implicit object mapping
arrangement for the portlet variables as yet.

I haven't tried the following approach yet myself but it _might_ work!

The usual MVC style of things is to populate a java bean (or beans)
prior to the JSP view page, store these beans in the appropriate scope
and then in the JSP page access the various variables from the beans.
In order to pass your bean/map into a portlet JSP page you could
extend a PortletRequestWrapper to include additional methods to do
things like create, populate and return a map of your variables.  In
your portlet code you would then pass the PortletRequestWrapper in the
include method of the invoking PortletRequestDispatcher.  Now you
should be able to access your variables from the wrapped portlet
request object using JSTL.  At no point are you directly accessing the
underlying HTTP session, request or context so this should be good
portlet practice.

Mark