Vaadin has nothing with beans and mapings directly. it is just a framework to create a rich ajax web interfaces. If you want help on mapping objects to tables, you have to read the manuals for the corresponding technology directly, for instance - hibernate, EJB3.
If you want to help on how to use already mapped entities of your business logic with UI’s build with Vadin - then you may take a look at Vaadin’s manual (Book of Vaading) and smapler demo as well as to HbnContainer (found in SVN/contrib).