NastavnikCrud

package manyToMany.crud;

import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.EntityTransaction;

import manyToMany.entities.Nastavnik;
import manyToMany.entities.Predmet;
import manyToMany.utils.PersistenceUtil;

public class NastavnikCrud {

    public static void dodajNastavnika (Nastavnik n) {
        EntityManager em = PersistenceUtil.getEntityManager();
        EntityTransaction et = null;

        try {
            et = em.getTransaction();
            et.begin();

            em.persist(n);
            em.flush();

            et.commit();
        } catch (Exception e) {
            System.err.println(e.getMessage());
            if (et != null)
                et.rollback();
        } finally {
            if (em != null && em.isOpen())
                em.close();
        }
    } // kraj dodajNastavnika

    public static void izbrisiNastavnika (Nastavnik n) {
        EntityManager em = PersistenceUtil.getEntityManager();
        EntityTransaction et = null;

        try {
            et = em.getTransaction();
            et.begin();

            List<Predmet> predaje = n.getPredmeti();

            for(Predmet p : predaje) {
                p.getNastavnici().remove(n);
                em.merge(p);
            }

            Nastavnik rem = em.merge(n);
            em.remove(rem);

            em.flush();
            et.commit();
        } catch (Exception e) {
            System.err.println(e.getMessage());
            if (et != null)
                et.rollback();
        } finally {
            if (em != null && em.isOpen())
                em.close();
        }
    } // kraj izbrisiNastavnika

    public static void dodajNastavnikuPredmet(Nastavnik n, Predmet p) {
        EntityManager em = PersistenceUtil.getEntityManager();
        EntityTransaction et = null;

        try {
            et = em.getTransaction();
            et.begin();

            n.getPredmeti().add(p);
            em.merge(n);

            p.getNastavnici().add(n);
            em.merge(p);

            em.flush();
            et.commit();
        } catch (Exception e) {
            System.err.println(e.getMessage());
            if (et != null)
                et.rollback();
        } finally {
            if (em != null && em.isOpen())
                em.close();
        }
    } // kraj dodajNastavnikuPredmet

}