Sorry, if I'm restating what you stated, but I just wanted to make sure I understand.
Are you needing to respond back to the user that the database update succeeded and if you fail to get a response back to the user, the transaction needs to be rolled back?
If so, you can maintain your database connection between
servlet calls ( remember maintaining your
jdbc connection with your session, multi-threading, etc.). I'm not sure off the top of my head if you can expect the instance to be the same between calls to a JSP, but this would be better suited to a servlet. The JSP should work if you use a bean to handle the connection, mapping to the session, database update, etc. I'm just not sure with the manner
Java Beans are instantiated.
You could just have the jsp reference the servlet with the post, have the servlet begin the transaction ( with a connection to the database that is maintained outside of the service/dopost method and tied to this user's session ). Then, if the user responds with a confirmation, or you complete your display of the page within the servlet, confirm your transaction, else rollback if you timeout or the user is not displayed a confirmation.
Let me know if I'm in the ball park, else, sorry for being useless. I'm studying for a certification tonight, but tomorrow pm I could continue this.
Good luck
David Taylor