PersistenceService.java

/*
 * Copyright 2011, Nabil Benothman, and individual contributors
 * as indicated by the @author tags. See the copyright.txt file in the
 * distribution for a full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
package com.ubike.rest.service;

import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.persistence.EntityManager;
import javax.transaction.UserTransaction;

/**
 * {@code PersistenceService}
 * <p>Utility class for dealing with persistence.</p>
 *
 * Created on Jun 6, 2011 at 7:17:22 PM
 *
 * @author <a href="mailto:nabil.benothman@gmail.com">Nabil Benothman</a>
 */
public class PersistenceService {

    private static String DEFAULT_PU = "ubikeEJB";
    private EntityManager em;
    private UserTransaction utx;
    private static ThreadLocal<PersistenceService> instance = new ThreadLocal<PersistenceService>() {

        @Override
        protected PersistenceService initialValue() {
            return new PersistenceService();
        }
    };

    /**
     * 
     */
    private PersistenceService() {
        try {
            //this.em = (EntityManager) new InitialContext().lookup("java:comp/env/persistence/" + DEFAULT_PU);
            this.em = (EntityManager) new InitialContext().lookup("java:comp/env/" + DEFAULT_PU);
            this.utx = (UserTransaction) new InitialContext().lookup("java:comp/UserTransaction");
        } catch (NamingException ex) {
            throw new RuntimeException(ex);
        }
    }

    /**
     * Returns an instance of PersistenceService.
     * 
     * @return an instance of PersistenceService
     */
    public static PersistenceService getInstance() {
        return instance.get();
    }

    /**
     * 
     */
    private static void removeInstance() {
        instance.remove();
    }

    /**
     * Returns an instance of EntityManager.
     *
     * @return an instance of EntityManager
     */
    public EntityManager getEntityManager() {
        return em;
    }

    /**
     * Begins a resource transaction.
     */
    public void beginTx() {
        try {
            utx.begin();
            em.joinTransaction();
        } catch (Exception ex) {
            throw new RuntimeException(ex);
        }
    }

    /**
     * Commits a resource transaction.
     */
    public void commitTx() {
        try {
            utx.commit();
        } catch (Exception ex) {
            throw new RuntimeException(ex);
        }
    }

    /**
     * Rolls back a resource transaction.
     */
    public void rollbackTx() {
        try {
            utx.rollback();
        } catch (Exception ex) {
            throw new RuntimeException(ex);
        }
    }

    /**
     * Closes this instance.
     */
    public void close() {
        removeInstance();
    }
}