EJB 3.0 Persistence with Oracle Enterprise Pack for Eclipse - EJB 3.0 Database Persistence with Oracle Fusion Middleware 11g - page 129

Similarly, create a CatalogTestBeanRemote interface by selecting Java | Interface in
the New window. The session bean class and the remote interface get added to the
EJB3JPA project.
The session bean class
The stateless session bean class, CatalogTestBean implements the
CatalogTestRemote interface. We shall use the EntityManager API to create,
find, query, and remove entity instances. Inject an EntityManager using
the @PersistenceContext annotation. Specify unitName as the same as the
persistence-unit name in the persistence.xml configuration file:
@PersistenceContext(unitName = "em")
EntityManager em;