import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
import java.net.URL;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import net.sf.hibernate.SessionFactory;
import net.sf.hibernate.Session;
import net.sf.hibernate.HibernateException;
import net.sf.hibernate.Databinder;
import net.sf.hibernate.cfg.Configuration;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;


public class HibernateListener
   implements HttpSessionListener, ServletContextListener {


    /**
     * the key under which the <code>SessionFactory</code> instance is stored
     * in the <code>ServletContext</code>.
     */
    public static final String SESSION_FACTORY_KEY = SessionFactory.class.getName();

    private static Log _log = LogFactory.getLog(HibernateListener.class);

    private static ServletContext context = null;

    /**
     * the path to the xml configuration file.  the path should start with a
     * '/' character and be relative to the root of the class path.
     * (DEFAULT:  "/hibernate.cfg.xml")
     */
    private String _configFilePath = "/hibernate.cfg.xml";
    private SessionFactory _factory = null;

   public HibernateListener() {
   }

   public void contextInitialized(ServletContextEvent sce) {
        Configuration configuration = null;
        URL configFileURL = null;
        context = null;

        try {
            configFileURL = HibernateListener.class.getResource(_configFilePath);

            context = sce.getServletContext();

            if (_log.isWarnEnabled()) {
                _log.debug("Initializing Hibernate from "
                        + _configFilePath + "...");
            }

            configuration = (new Configuration()).configure(configFileURL);
            _factory = configuration.buildSessionFactory();
            _log.debug("Storing SessionFactory in ServletContext...");
            context.setAttribute(SESSION_FACTORY_KEY, _factory);


        } catch (Throwable t) {
            _log.error("Exception while initializing Hibernate.");
            System.out.println("Exception while initializing Hibernate.");
            t.printStackTrace();
        }
   }


   public void contextDestroyed(ServletContextEvent sce) {

        try {
            _log.debug("Destroying SessionFactory...");
            _factory.close();
            _log.debug("SessionFactory destroyed...");
        } catch (Exception e) {
            _log.error("Unable to destroy SessionFactory...(exception ignored)",
                    e);
        }
   }

   public void sessionCreated(HttpSessionEvent se) {
        //required by Listener contract.  We're creating Hibernate sessions per-request so we don't care about this.
   }

   public void sessionDestroyed(HttpSessionEvent se) {
        //required by Listener contract.
   }

    public static SessionFactory sessionFactory(HttpServletRequest request)
            throws HibernateException {
        Object sf = context.getAttribute(SESSION_FACTORY_KEY);
        if (null == sf) {
            throw new HibernateException(SESSION_FACTORY_KEY);
        }
        return (SessionFactory) sf;
    }
    public static Session open(HttpServletRequest request) throws HibernateException {

        Session sess = null;
        try {
            sess = sessionFactory(request).openSession();
        } catch (HibernateException e) {
            e.printStackTrace();
        }

        return sess;

    }

    public static Databinder openDB(HttpServletRequest request) throws HibernateException {

        Databinder db = null;
        try {
            db = sessionFactory(request).openDatabinder();
        } catch (HibernateException e) {
            e.printStackTrace();
        }

        return db;

    }

}