these're my classes
---
public class ToolStudente {
    public List listaStudenti () {
        Session session =
HibernateUtil.getSessionFactory().getCurrentSession();
        session.beginTransaction();
        List result = session.createQuery("from Studenti").list();
        session.getTransaction().commit();
        return result;
    }
}
---
public class HibernateServlet extends javax.servlet.http.HttpServlet
implements javax.servlet.Servlet {
    public HibernateServlet() {super();}

    protected void service(HttpServletRequest request, HttpServletResponse
response) throws ServletException, IOException {

        ToolStudente ts = new ToolStudente();
        List studenti = ts.listaStudenti();
        for (int i=0; i < studenti.size(); i++){
            Studenti thestudent = (Studenti) studenti.get(i);
            System.out.println("Studente: " + thestudent.getCognome() +
thestudent.getNome()
                    + " matricola: "+ thestudent.getMatricola());
    }
}
---
public class HibernateUtil {

    private static final SessionFactory sessionFactory;
    static {
        try {
            // Create the SessionFactory from hibernate.cfg.xml
            sessionFactory = new
Configuration().configure().buildSessionFactory();
        } catch (Throwable ex) {
            // Make sure you log the exception, as it might be swallowed
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }

    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }
   
}