JSF-1.2-Question. Strategy for saving current application-state(managed bean state) when redirecting to external service

Definition --

• There is working web-app with managed-bean state at some point.
• this web-app posts request to external-开发者_开发知识库application

• External-application calls-back(http 'get' method) to web-app

  -- At this time application should restore managed-bean state as it was before request to external application.

  -- Note: External-app may respond later, than web-app session duration last.

Question -- If there are patterns or techniques around this kind of problem in JSF?

What is your way dealing with problem like this?

Store the state in the session scope along with an unique key and include that key as request parameter or pathinfo in the callback URL. When the callback request is received, extract the key from the request parameter or pathinfo and then obtain the state from the session based on that key.