This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
Is this a stand alone or distributed application?
As such it is a bad design to have any of your GUI classes talk to the DB directly. Usually one would have a dedicated class which talks to the DB at one end and with the GUI at the other end.
Depending on the complexity of your application, you might opt for a simple JDBC approach or more flexible like say Hibernate to talk to your DB
Polling might be a good option. I am not aware of any frameworks which will fire notifications to your application in case of any changes. You might want to search the forums. I get a feeling this problem has been discussed before.