How can I pass information from one portlet to another?

Question

First, some background...
I am using Portal 5.0.2 and developing portlets using JSP/Java on a remote server.
I need to pass information from a portlet on pageA to another portlet on pageB, but I can't do it using the traditional methods, such as query string, session, cookies, etc. due to either portal framework limitations or because of functional constraints (basically, a user will not necessarily be logged in to the portal, but he can view anything available to the GUEST user). Here are the different ways I've considered using to save state and their limitations:
Query string: can't use this because portlets on remote servers don't have access to it
Cookies: if user disables cookies, code will not function properly
Session variables: limited to one user's connection with one portlet (i.e., can't access a session variable set in portletA from portletB)
Application variables: because the user may not be logged in, I have no way of uniquely naming variables, which is a necessity in order to maintain state for EACH user
User Settings: again, the user may not be logged in, so I can't use these
PCC: can't access client-side variables because server-side JSP executes first
Are my assumptions above correct? Has anyone had any success using one of these methods given the same constraints, or does anyone have an alternative solution? I'd certainly appreciate any help anyone could provide.
Thanks,
Jose

Answer 1

One possibility would be to use a Login PEI to set a unique UserInfo Name/Value for the user. I think in 5.0 each guest session is unique, so would have unique UserInfo. Then you could pass this value to your portlet (by specifying it in the web service) and use it as a key into a Application-scoped hashmap where you store your info. In other words, your Application variables option, but you have a way of uniquely naming your variables via PEI-set UserInfo.