Classe DAO Genérica

public class Dao<T> implements Serializable{
    
    private EntityManagerFactory emf = null;
    
    public Dao(){
        this.emf = Persistence.createEntityManagerFactory("PadariaPU");
    }
    
    public EntityManager getEntityManager(){
        return emf.createEntityManager();
    }
    
    public void create(T obj){ //ok
        EntityManager em = null;        
        try {
            em = getEntityManager();
            em.getTransaction().begin();
            em.persist(obj);
            em.getTransaction().commit();
        }finally{
            if (em != null){
                em.close();
            }
        }
    }
    
    public void edit(T obj, int id, Class<T> classe) throws Exception{ //ok
        EntityManager em = null;
        try {
            em = getEntityManager();
            em.getTransaction().begin();
            obj = em.merge(obj);
            em.getTransaction().commit();
        }catch(Exception ex){
            String msg = ex.getLocalizedMessage();
            if(msg == null || msg.length() == 0){                
                if(findObject(id, classe) == null){
                    throw new Exception("The clientes with id " + id + " no longer exists.");
                }
            }
            throw ex;
        }finally{
            if(em != null){
                em.close();
            }
        }
    }
    
    public void destroy(int id, Class<T> classe) throws Exception{ //ok
        EntityManager em = null;
        try{
            em = getEntityManager();
            em.getTransaction().begin();           
            try{
                 em.remove(em.getReference(classe, id));                
            }catch(EntityNotFoundException enfe){
                throw new Exception("The clientes with id " + id + " no longer exists.", enfe);
            }          
            em.getTransaction().commit();
        }finally{
            if(em != null){
                em.close();
            }
        }
    }

    public List<T> findEntities(Class<T> classe){ //ok
        return findEntities(true, -1, -1, classe);
    }

    public List<T> findEntities(int maxResults, int firstResult, Class<T> classe){ //ok
        return findEntities(false, maxResults, firstResult, classe); 
    }

    private List<T> findEntities(boolean all, int maxResults, int firstResult, Class<T> classe){ //ok
        EntityManager em = getEntityManager();
        try {
            CriteriaQuery cq = em.getCriteriaBuilder().createQuery();
            cq.select(cq.from(classe));
            Query q = em.createQuery(cq);
            if (!all) {
                q.setMaxResults(maxResults);
                q.setFirstResult(firstResult);
            }
            return q.getResultList();
        } finally {
            em.close();
        }
    }

    public T findObject(int id, Class<T> classe){ //ok
        EntityManager em = getEntityManager();
        try {
            return em.find(classe, id);
        } finally {
            em.close();
        }
    }

    public int getClientesCount(Class<T> classe){ //ok
        EntityManager em = getEntityManager();
        try {
            CriteriaQuery cq = em.getCriteriaBuilder().createQuery();
            Root<T> rt = cq.from(classe);
            cq.select(em.getCriteriaBuilder().count(rt));
            Query q = em.createQuery(cq);
            return ((Long) q.getSingleResult()).intValue();
        } finally {
            em.close();
        }
    }    
}