public List<DVD> findByCategory(String param_category) {

		List<DVD> dvds = new ArrayList<DVD>();
		String query = "SELECT * FROM dvd WHERE category=?";
		em = dbUtil.getEntityManager();
		Query q = em.createNativeQuery(query, DVD.class);
		q.setParameter(1, param_category);
		dvds = q.getResultList();
		return dvds;

	}