public interface User
{
int getId();
void setId(int id);
UserRole getUserRole();
void setUserRole(UserRole userRole);
String getName();
void setName(String name);
String getPhone();
void setPhone(String phone);
String getEmail();
void setEmail(String email);
}

@Entity
@NamedQuery(name = "GenericUser.findAll", query = "SELECT u FROM GenericUser u")
public class GenericUser implements User {

@Id
@GeneratedValue()
private int id;
private UserRole userRole;
private String name;
private String phone;
private String email;

public GenericUser(int id, UserRole userRole, String name, String phone, String email) {
    this.id = id;
    this.userRole = userRole;
    this.name = name;
    this.phone = phone;
    this.email = email;
}

public GenericUser(UserRole userRole, String name, String phone, String email){
    this.userRole = userRole;
    this.name = name;
    this.phone = phone;
    this.email = email;
}

public GenericUser(){
}
....get/set....

public interface DAO<T>
{
T findById(int id);
Collection<T> findAll();
void save(T t);
void update(T t);
void delete(T t);
void delete(Collection <T> tCollection);
}

@TransactionManagement(value= TransactionManagementType.CONTAINER)
@TransactionAttribute(value=REQUIRED)
public abstract class AbstractJpaDao<T> implements DAO<T>
{
private static final Logger LOG = Logger.getLogger(AbstractJpaDao.class);

@PersistenceContext(unitName = "cwPU")
protected EntityManager entityManager;

@Override
public abstract T findById(int id);

@Override
public abstract Collection<T> findAll();

@Override
public void save(T t){
    LOG.debug("saving " + t);
    entityManager.persist(t);
}

@Override
public void update(T t){
    entityManager.refresh(t);
}

@Override
public void delete(T t){
    delete(Collections.singletonList(t));
}

@Override
public void delete(Collection<T> collection){
    for (T t : collection){
        entityManager.remove(t);
    }
}

@PreDestroy
private void closeEntityManager(){
    entityManager.close();
}
}

@Stateless
@Local(cw.data.DAO.class)
public class GenericUserJpaDao extends AbstractJpaDao<User>
{
private static final Logger LOG = Logger.getLogger(GenericUserJpaDao.class);
@Override
public User findById(int id){
    LOG.debug("find by id: " + id);
    return entityManager.find(GenericUser.class, id);
}

@Override
public Collection<User> findAll(){
    TypedQuery<GenericUser> genericOrderTypedQuery = entityManager.createNamedQuery("GenericUser.findAll", GenericUser.class);
    Collection<User> usersToReturn = new ArrayList<User>();
    usersToReturn.addAll(genericOrderTypedQuery.getResultList());
    return usersToReturn;
}

@Override
public void save(User user) {
    LOG.debug("saving user " + user.getId());
    super.save(user);
}
}

public class CreateUserObject extends HttpServlet {
@EJB
DAO<User> userDAO;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    GenericUser genericUser = new GenericUser();
    genericUser.setId(0);
    genericUser.setEmail("sample");
    genericUser.setName("name");
    genericUser.setPhone("1");
    genericUser.setUserRole(UserRole.ADMIN);
    userDAO.save(genericUser);
    Collection<User> users = userDAO.findAll();
    resp.getWriter().write("size - " + users.size());
    for (User user : users){
        resp.getWriter().write("id - " + user.getId());
    }
}
}

<persistence-unit name="cwPU" transaction-type="JTA">
    <provider>org.hibernate.ejb.HibernatePersistence</provider>
    <properties>
        <property name="hibernate.connection.driver_class" value="oracle.jdbc.driver.OracleDriver"/>
        <property name="hibernate.connection.url" value="jdbc:oracle:thin:@localhost:1521:xe"/>
        <property name="hibernate.connection.username" value="cw"/>
        <property name="hibernate.connection.password" value="cw"/>
        <property name="hibernate.dialect" value="org.hibernate.dialect.Oracle10gDialect"/>
        <property name="hibernate.hbm2ddl.auto" value="create"/>
    </properties>
</persistence-unit>