@Path("/helloworld")
public class HelloWorld {

1  // @EJB
2  // private MySessionBean sessionBean;

    @GET
    @Produces("text/plain")
    public String getClichedMessage() {
        try {
3            Context ctx = new InitialContext();
4           sessionBean = (MySessionBean) ctx.lookup("java:global/RestTest/MySessionBean");

            return sessionBean.request();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return "error";
    }
}

@Stateless
public class MySessionBean {
    public MySessionBean() {
    }

    public String request() {
        return "HELLO from SessionBean";
    }
}

public abstract class BasicService<E extends BasicDomain>

public abstract class BasicBean <E extends BasicDomain> {

    @PersistenceContext
    private EntityManager entityManager;

    @EJB
    protected DAO dao;

    protected abstract Class<E> getDomain();

    public List<E> findAll() {
        return dao.findAll(getDomain());
    }

    public E find(long id) {
        return dao.find(getDomain(), id);
    }

    public void delete (long id) {
        dao.delete(getDomain(), id);
    }

    @Inject
    private DAO dao;

    @Path("/delete/{id}")
    @DELETE
    public void delete(@PathParam("id") long id) {
        getBean().delete(id);
    }

    @Path("/create")
    @PUT
    public CustomerDomain create(@QueryParam("lastName") String lastName,
                                 @QueryParam("firstName") String firstName,
                                 @QueryParam("phone") String phone) {

        return customerBean.create(lastName, firstName, phone);
    }

    @Path("/update")
    @POST
    @Consumes("application/x-www-form-urlencoded")
    public CustomerDomain update(@FormParam("id") long id,
                       @FormParam("lastName") String lastName,
                       @FormParam("firstName") String firstName,
                       @FormParam("phone") String phone) {
        return customerBean.update(id, lastName, firstName, phone);

1. REST - Presentation Layer
в нем классы такого вида
@RequestScoped
@Path("/customers")
@Produces("text/xml")
public class CustomersService {

    @EJB
    private CustomerBean customerBean;
..............
    @Path("/create")
    @PUT
    @Consumes("application/x-www-form-urlencoded")
    public CustomerDomain create(@FormParam("lastName") String lastName,
                                 @FormParam("firstName") String firstName,
                                 @FormParam("phone") String phone) {

        return customerBean.create(lastName, firstName, phone);
    }
..........
}

2. EJB, DAO - Business Layer
@Stateless(name = "CustomerBean")
public class CustomerBean {

    @Inject
    private DAO dao;

    @PersistenceContext
    EntityManager entityManager;
..............................
    public CustomerDomain create(String lastName, String firstName, String phone) {

        CustomerDomain customerDomain = new CustomerDomain();
        customerDomain.setLastName(lastName);
        customerDomain.setFirstName(firstName);
        customerDomain.setPhone(phone);

        return dao.create(customerDomain);
    }
...............................
}

3. Domain - Data Layer.
тут из Java -сущности, persistence.xml 
а также собственно БД.