to manage your own mapping between url and page/window, and manage the parameter your way, you should write your own url mapping service.
You can look at the CMSPortlet object that works with it's own mapping for url like ...portal/content/myFile.html and rely on the CMS repository to get the file.
see the doc, about the CMS and the prefix of the url for files in the cms repository. there is an explaination about this... and that is a good start.
then look at services like :
(these are defined in a jboss-service.xml file, in meta-inf folder)
and classes such as CMSObjectURLFactory and CMSObjectCommandFactory
portal 2.4 has been enhanced for managing this : for what I have just seen, you should be able to manage several prefixes, with several window target.
I think either you misunderstand what it is I need, or else I misunderstand the complexity of this task.
All I want is to construct a URL that points to the existing web page, from within a portlet, which is already mapped by JBoss Portal to execute the portlets, etc. I do not need any custom URL mappings to create special behavior when that URL is accessed.
Followup: the issue was using the url in a form, with GET method. Found out form needs to be sent with POST method, and the url needs to be an action URL, not a render url.