How can i let Displaytag work in an Oracle 10g Portal environment?

Question

Hi there,
I'm already searching and trying this for a week, but didn't succeed yet.
I want to use displaytag to be able to sort and page data in a HTML table on a very generic and easy-to-use way.
Locally in JDeveloper 10.1.3 on OC4J (embedded) it works like a charm (even exporting with the export filter).
On portal...it "sucks" :-s ... It doesn't work at all. It displays the data, but when i click a column for sorting, or a another page of the displaytag an error occurs.
If i do nothing (except giving requestURI="") , the portal suddenly displays it's toplevel page.
If i try to compose the requestURI in the JSP itself, and get the approximate URI that the oracle portal needs, the action is called, but apparently our http session is invalidated, i get nullpointers of an object that should be on the request.getSession(), but it is null there.
I already tried something like implementing the PortletRequestHelper and PortletHref , but therefore i need access to the request (or pageContext?) attributes renderResponse and portletRequest, that should be in the request or page as an attribute with a given name.
I have already printed all session, request and pagecontext attributes and their names in a header.jsp (included like <%@ include file="header.jsp"%> ) , but no objects like javax.portlet.PortletRequest or javax.portlet.RenderResponse appear to be there.
So i can't fetch them from the PageContext attribute in my custom PortletRequestHelper implementation.
Well :-s I need help urgently. Can anyone give me more information to this? I already googled, searched different sources, addressed some colleagues here, and nothing could help me. You, Oracle experts, are my last hope. (Normally, i have a colleague who is very known with Oracle Portal, Oracle expert in our company, but he's ill).
It must have something to do with a wrong URL, but i checked the URL generated by portal for a tab that we can click to change pages, and the URL generated by portal on the displaytag column headers ... (in my current code with the hand-written requestURI in the JSP itself) , and it is completely the same, only 2 request parameters are added. If i click the column, it gives a nullpointerexception on an object that should be on the session but is null.
If you need more information, i'll be so kind as to answer your questions.
I hope this explanation was clear enough :-s i'm quite aggitated that i can't get this wonderfull displaytag working in oracle portal.
Kind regards,
Steve

Answer 1

Hi there :-)
Thanks already for your replies.
Well, i checked PortletRenderRequest and responses already ... But well ...
I have to re-implement the PortletRequestHelperFactory to allow displaytag to generate the links.
Displaytag expects me to make a PortletRequestHelperFactory (AbsentPortletRequestHelperFactory --> The project call Absenteisme ... employees that are absent from work are registered) that gives a pageContext parameter to an AbsentPortletRequestHelper.
The PortletHref that i need to re-implement (AbsentPortletHref), is constructed using a PortletRequest and a PortletResponse parameter, like the default PortletHref in de Displaytag-Portlet source.
PortletRequest and PortletRenderRequest aren't the same, this gives ClassCastExceptions, and other problems. I already tried using wrappers but can't find anything that works.
:-s
I really don't know further what to do, except indeed working with the correct objects, but how then override those porltet helper objects.
Anyone experience with sorting / paging displaytag in oracle portal ? (I already read that export of displaytag data might pose problems in oracle portal, but this isn't a primary concern ... first i need sortable and pageable data working in Oracle Portal).