Your SFSB will have to query your external service layer.
Perhaps external service puts all incoming messages in a database (in memory or not...), and SFSB queries this database
Thanks, DB is one way to interface with SFSB on the results and would be a good working solution when the results should be kept for later usage.
There are some cases (trivial) when it may not be necessary to keep in DB, for example, the result is the price of the selected car and the web page is showing the last 10 queries of the prices.
Not sure if the following can work, haven't test yet:
client --(return result via JMS)--- a MDB and application scope that keep the results in memory (by lists, etc)
The SFSB can query the MDB and application scope class.
Basically the SFSB should query a singleton, not sure if that MDB and application scope class can be a singleton.