package auction.web.filter;import org.apache.commons.logging.*;import org.hibernate.*;import auction.persistence.HibernateUtil;import javax.servlet.*;import javax.servlet.Filter;import java.io.IOException;/** * Filter that manages a Hibernate Session for a request. * <p> * This filter should be used if your <tt>hibernate.current_session_context_class</tt> * configuration is set to <tt>thread</tt> and you are not using JTA or CMT. * <p> * With JTA you'd replace transaction demarcation with calls to the <tt>UserTransaction</tt> API. * With CMT you would remove transaction demarcation code from this filter. * <p> * An alternative, more flexible solution is <tt>SessionTransactionInterceptor</tt> * that can be applied to any pointcut with JBoss AOP. * <p> * Note that you should not use this interceptor out-of-the-box with enabled optimistic * concurrency control. Apply your own compensation logic for failed conversations, this * is totally dependent on your applications design. * * @see auction.persistence.SessionTransactionInterceptor * * @author Christian Bauer */public class HibernateSessionRequestFilter implements Filter {    private static Log log = LogFactory.getLog(HibernateSessionRequestFilter.class);    private SessionFactory sf;    public void doFilter(ServletRequest request,                         ServletResponse response,                         FilterChain chain)            throws IOException, ServletException {        try {            log.debug("Starting a database transaction");            sf.getCurrentSession().beginTransaction();            // Call the next filter (continue request processing)            chain.doFilter(request, response);            // Commit and cleanup            log.debug("Committing the database transaction");            sf.getCurrentSession().getTransaction().commit();        } catch (StaleObjectStateException staleEx) {            log.error("This interceptor does not implement optimistic concurrency control!");            log.error("Your application will not work until you add compensation actions!");            // Rollback, close everything, possibly compensate for any permanent changes            // during the conversation, and finally restart business conversation. Maybe            // give the user of the application a chance to merge some of his work with            // fresh data... what you do here depends on your applications design.            throw staleEx;        } catch (Throwable ex) {            // Rollback only            ex.printStackTrace();            try {                if (sf.getCurrentSession().getTransaction().isActive()) {                    log.debug("Trying to rollback database transaction after exception");                    sf.getCurrentSession().getTransaction().rollback();                }            } catch (Throwable rbEx) {                log.error("Could not rollback transaction after exception!", rbEx);            }            // Let others handle it... maybe another interceptor for exceptions?            throw new ServletException(ex);        }    }    public void init(FilterConfig filterConfig) throws ServletException {        log.debug("Initializing filter...");        log.debug("Obtaining SessionFactory from HibernateUtil");        sf = HibernateUtil.getSessionFactory();    }    public void destroy() {}}