HibernateUtil 的写法

package com.stu.persistence;

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class HibernateUtil {

    private static final SessionFactory sessionFactory;

    static {
        try {
            sessionFactory = new Configuration().configure().buildSessionFactory();
        } catch (HibernateException ex) {
            throw new RuntimeException("Exception building SessionFactory: "
                    + ex.getMessage(), ex);
        }
    }

    public static Session currentSession() throws HibernateException {
        Session s = sessionFactory.openSession();
        return s;
    }

    public static void closeSession(Session s) {
        s.close();
    }
}