Extracting userId from SAP Logon ticket

We are getting a validated SAP Logon ticket genearted by SAP Netweaver engine.

Our J2EE application which is deployed on the same Netweaver APP server and the SAP Logon ticket is passed in the http request.

Question: Is there a way to extract the user ID from the ticket? We need not validate the ticket again, but only need to extract the user id. Any sample code or pseudo code will be helpful.

Thanks,

- Shankar