Although JPA is part of Java EE 6, it merits its own section.
JPA is very similar to Hibernate, in that it is the standardized way to access database, whereas Hibernate is a proprietary approach.
The add-on directory also offers a container able to use JPA 1.0: the Vaadin JPA Container. The add-on is certified by the Vaadin Company, note that it is available under either the AGPL license if your project is compatible or a commercial license.
We won't go into further details here as most concepts are very similar to Hibernate container. Moreover, we also used JPA mappings for our previous example. Anyway, knowing this add-on exists can be a lifesaver.