devX.com’s Java site have a worked example of building a simple music store application using EJB3.0 persistence. The sample code is built using Maven and deployed to JBoss4.0.3.
The example code shows how easy it is (in comparison to the EJB2.x Entity Bean approach) to map POJO entities to tables and columns using Java SE 5.0 annotations, and then manipulate them with the EntityManager API.