Re: JPA in practice

public class Util
{
private static final String PUNIT = "projectPU";
private static final EntityManagerFactory EMFCANON =
  Persistence.createEntityManagerFactory( PUNIT );

public static EntityManagerFactory getEmf()
{
  return EMFCANON;
}
}

The factory will be heavy but thread safe. Request processors get their
lightweight, non-thread-safe EntityManagers from the common factory:

public class BizProcess
{ ...
public String submit()
{
  EntityManager emgr = Util.getEmf().createEntityManager();
  try
  {
   Entity e = new Entity();
   fill( e );
   emgr.getTransaction().begin();
   emgr.merge( e );
   emgr.getTransaction().commit();
  }
  finally
  {
    emgr.close();
  }
}
}

Not as sexy as @PersistenceContext() but it works.