Why do you need to do that?
What is exactly your requirements?
Usually you don't need to get data from portal requests in Alfresco, usually you can get all this data from a standard portlet and then you can invoke with one of the Alfresco APIs repository to read or write contents.
Alfresco is a standard web application so if you really would like to do this in Alfresco, you could have need to use one of the class in portlet-api.jar but this is not a good solution because depends on portal vendors. So I suggest you not to follow this solution.
Let me know more information please.
Hope this helps.