I'm trying to save data acquired by Rest web service to database using hibernate/persistence.

In one of my web modules i implemented that service. Database ejb connector is placed in EJB module. They are parts of EAR application.

Every time when i call pb.addDevice() im getting  java.lang.NullPointerException when puting proper url with params in browser(worked till i wanted to save it to Database). Can't find what is wrong with it. I'm using jboss 6.1.0 Final.

PS. when i changed from

    @EJB

    PersistenceBean pb;

to

    PersistenceBean pb = new PersistenceBean();

i got null pointer on  EntityManager em = emf.createEntityManager();

code:

    @Stateless

    @Path("/RestService")

    public class RestPush  {

    @EJB

    PersistenceBean pb;

        @GET

          @Path("/RegisterDevice")

        public void registerDevice(

            @QueryParam("deviceId") String deviceId){

            Device d = new Device(true);

            d.setId = deviceId;

            pb.addDevice(d);

        }

    }

and EJB class:

    @Stateless(mappedName = "PersistenceBean")

    public class PersistenceBean {

    @PersistenceUnit(unitName = "PersistentUnitName")

    EntityManagerFactory emf;

    private void persist(Object o, EntityManager entityManager) {

        try {

            entityManager.persist(o);

        } catch (Exception e) {

            logger.severe("Error writing to DB: " + e);

            logger.severe("" + e.fillInStackTrace());

        }

    }

      public void addDevice(Device d) {

        try {

            EntityManager em = emf.createEntityManager();

        if (persist(device, em)) {

                logger.info("Device with id : " + device.getId()

                        + " has been added ");

    } else {

                logger.info("Failed to add device with id: " + device.getId());

    } catch (Exception e) {

            logger.severe("PersistenceBean: Could not save device.");

            e.printStackTrace();

    }

    }