/* Copyright (C) 2011, 2012, 2013 by Bundesanstalt für Gewässerkunde
 * Software engineering by Intevation GmbH
 *
 * This file is Free Software under the GNU AGPL (>=v3)
 * and comes with ABSOLUTELY NO WARRANTY! Check out the
 * documentation coming with Dive4Elements River for details.
 */

package org.dive4elements.river.backend;

import org.apache.log4j.Logger;

import org.hibernate.Session;
import org.hibernate.SessionFactory;


public class SessionHolder
{
    private static Logger log =
        Logger.getLogger(SessionHolder.class);

    public static final ThreadLocal<Session> HOLDER =
        new ThreadLocal<Session>() {
            @Override
            protected Session initialValue() {
                Session session = create();
                log.debug("Initial session value: " + session.hashCode());
                return session;
            }
        };

    protected SessionHolder() {
    }

    public synchronized static Session create() {
        log.debug("create");
        SessionFactory sessionFactory =
            SessionFactoryProvider.getSessionFactory();
        return sessionFactory.openSession();
    }

    public static Session acquire() {
        Session session = create();
        log.debug("acquired session: " + session.hashCode());
        HOLDER.set(session);
        return session;
    }

    public static void release() {
        Session session = HOLDER.get();
        if (session != null) {
            log.debug("releasing session: " + session.hashCode());
            try {
                if (!session.isOpen()) {
                    /* If this check really works in all cases why does hibernate
                     * does not use it when you call close anyway. */
                    log.debug("Session is not open. Calling close anyway.");
                }
                session.close();
            } catch (Exception e) {
                /* Do not try this at home. But hibernate may fail with an NPE
                 * or any other exception depending on the state of the session.
                 * According to doc this should only throw a HibernateException but
                 * we definetely get NPE's here.
                 */
                log.error("Exception caught on session close! Session already closed?" + e.getMessage());
            }
        } else {
            log.debug("release called on NULL session.");
        }
        HOLDER.remove();
    }
}
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