public class HibernateSessionFactory {

    private static final Logger logger = Logger.getLogger(HibernateSessionFactory.class);
    private SessionFactory sessionFactory;
    private static HibernateSessionFactory _instance = null;
    private static int counter = 0;
   
    /**
     * Session is a thread local so that each thread has its own copy
     */
    public static final ThreadLocal session = new ThreadLocal();
   
    /**
     * Hidden constructor
     */
    private HibernateSessionFactory() {
        super();
       
        try {

            // Create the SessionFactory
            //
            sessionFactory = new Configuration().configure().buildSessionFactory();

        } catch (HibernateException ex) {
           
            // something went wrong. Rethrow and catch
            //
            logger.fatal(ErrorCodes.getString(ErrorCodes.DB_ERROR_SESSION_CREATE), ex);
            throw new RuntimeException(ErrorCodes.getString(ErrorCodes.DB_ERROR_SESSION_CREATE), ex);

        }
       
    }


    /**
     * Returnt the only instance of this session factory
     *
     * @return Session factory
     */
    public static HibernateSessionFactory getInstance() {

        if (_instance == null) {
            _instance = new HibernateSessionFactory();
            counter += 1;
            return _instance;
        } else {
            return _instance;
        }
    }


    /**
     * Obtain a hibernate session
     *
     * @return A valid a Hibernate session
     * @throws HibernateException
     */
    public Session getSession() throws HibernateException {

        // try to get a valid session
        //
        Session s = (Session) session.get();

        // Open a new Session, if this Thread has none yet
        //
        if (s == null) {

            // lets get a new session
            //
            s = sessionFactory.openSession();

            session.set(s);
        }

        // return an active session
        //
        return s;
    }

    /**
     * Disconnect and close a session
     *
     * @throws HibernateException
     */
    public void closeSession() throws HibernateException {
       
        // extract the local session
        //
        Session s = (Session) session.get();
        session.set(null);

        if (s != null) {
           
            // notify the session that the transaction completed, so we no
            // longer own the old locks. (Also we should release cache softlocks.)
            // may be called multiple times during the transaction completion process.
            // calling disconnect on the session has the effect of calling
            // afterTransactionComplete(true);
            //
            s.disconnect();
           
            // close the session
            //
            s.close();
        }
    }

}

public class HibernateSessionFactory {

    private static final Logger logger = Logger.getLogger(HibernateSessionFactory.class);
    private static SessionFactory sessionFactory;
   
    /**
     * Session is a thread local so that each thread has its own copy
     */
    public static final ThreadLocal session = new ThreadLocal();
   
    static {
        try {
            // Create the SessionFactory
            sessionFactory = new Configuration().configure().buildSessionFactory();
        } catch (Throwable ex) {
            logger.error("Initial SessionFactory creation failed.", ex);
            throw new ExceptionInInitializerError(ex);
        }
    }

       
    /**
     * Obtain a hibernate session
     *
     * @return A valid a Hibernate session
     * @throws HibernateException
     */
    public static Session getSession() throws HibernateException {

        // try to get a valid session
        //
        Session s = (Session) session.get();

        // Open a new Session, if this Thread has none yet
        //
        if (s == null) {

            // lets get a new session
            //
            s = sessionFactory.openSession();

            session.set(s);
        }

        // return an active session
        //
        return s;
    }

    /**
     * Disconnect and close a session
     *
     * @throws HibernateException
     */
    public static void closeSession() throws HibernateException {
       
        // extract the local session
        //
        Session s = (Session) session.get();
        if (s != null) {
           
            // Completely clear the session. Evict all loaded instances
            // and cancel all pending saves, updates and deletions.
            // Do not close open iterators or instances of
            // ScrollableResults
            //
            s.clear();
           
            // notify the session that the transaction completed, so we no
            // longer own the old locks. (Also we should release cache softlocks.)
            // may be called multiple times during the transaction completion process.
            // calling disconnect on the session has the effect of calling
            // afterTransactionComplete(true);
            //
            s.disconnect();
           
            // close the session
            //
            s.close();
        }
       
        session.set(null);
    }

}