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package com.discursive.dao.generic.hibernate;

import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;
import org.apache.log4j.Logger;
import org.hibernate.FlushMode;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.springframework.beans.factory.annotation.Required;
import org.springframework.dao.DataAccessResourceFailureException;
import org.springframework.orm.hibernate3.SessionFactoryUtils;
import org.springframework.orm.hibernate3.SessionHolder;
import org.springframework.transaction.support.TransactionSynchronizationManager;

public class OpenSessionInterceptor implements MethodInterceptor {

    public static final Logger logger = Logger.getLogger( OpenSessionInterceptor.class );
    
    private SessionFactory sessionFactory;
    
    private boolean singleSession = true;

    /**
     * Get a Session for the SessionFactory that this filter uses.
     * Note that this just applies in single session mode!
     * The default implementation delegates to SessionFactoryUtils'
     * getSession method and sets the Session's flushMode to NEVER.
     * 
Can be overridden in subclasses for creating a Session with a custom
     * entity interceptor or JDBC exception translator.
     * @param sessionFactory the SessionFactory that this filter uses
     * @return the Session to use
     * @throws DataAccessResourceFailureException if the Session could not be created
     * @see org.springframework.orm.hibernate3.SessionFactoryUtils#getSession(SessionFactory, boolean)
     * @see org.hibernate.FlushMode#NEVER
     */
    @SuppressWarnings("deprecation")
    protected Session getSession(SessionFactory sessionFactory) throws DataAccessResourceFailureException {
        Session session = SessionFactoryUtils.getSession(sessionFactory, true);
        //session.setFlushMode(FlushMode.NEVER);
        session.setFlushMode(FlushMode.MANUAL);
        return session;
    }

    /**
     * Close the given Session.
     * Note that this just applies in single session mode!
     * 
The default implementation delegates to SessionFactoryUtils'
     * releaseSession method.
     * 
Can be overridden in subclasses, e.g. for flushing the Session before
     * closing it. See class-level javadoc for a discussion of flush handling.
     * Note that you should also override getSession accordingly, to set
     * the flush mode to something else than NEVER.
     * @param session the Session used for filtering
     * @param sessionFactory the SessionFactory that this filter uses
     */
    protected void closeSession(Session session, SessionFactory sessionFactory) {
        SessionFactoryUtils.releaseSession(session, sessionFactory);
    }

    public Object invoke(MethodInvocation invocation) throws Throwable {
        Object returnObject;
        Session session = null;
        boolean participate = false;

        if (singleSession) {
            // single session mode
            if (TransactionSynchronizationManager.hasResource(sessionFactory)) {
                // Do not modify the Session: just set the participate flag.
                participate = true;
            }
            else {
                logger.debug("Opening single Hibernate Session in OpenSessionInViewFilter");
                session = getSession(sessionFactory);
                TransactionSynchronizationManager.bindResource(sessionFactory, new SessionHolder(session));
            }
        }
        else {
            // deferred close mode
            if (SessionFactoryUtils.isDeferredCloseActive(sessionFactory)) {
                // Do not modify deferred close: just set the participate flag.
                participate = true;
            }
            else {
                SessionFactoryUtils.initDeferredClose(sessionFactory);
            }
        }

        try {
            returnObject = invocation.proceed();
        }

        finally {
            if (!participate) {
                if (singleSession) {
                    // single session mode
                    TransactionSynchronizationManager.unbindResource(sessionFactory);
                    logger.debug("Closing single Hibernate Session in OpenSessionInViewFilter");
                    try {
                        closeSession(session, sessionFactory);
                    }
                    catch (RuntimeException ex) {
                        logger.error("Unexpected exception on closing Hibernate Session", ex);
                    }
                }
                else {
                    // deferred close mode
                    SessionFactoryUtils.processDeferredClose(sessionFactory);
                }
            }
        }
        return returnObject;
    }

    @Required
    public void setSessionFactory(SessionFactory sessionFactory) {
        this.sessionFactory = sessionFactory;
    }

    /**
     * Set whether to use a single session for each request. Default is "true".
     * If set to false, each data access operation or transaction will use
     * its own session (like without Open Session in View). Each of those
     * sessions will be registered for deferred close, though, actually
     * processed at request completion.
     * @see SessionFactoryUtils#initDeferredClose
     * @see SessionFactoryUtils#processDeferredClose
     */
    public void setSingleSession(boolean singleSession) {
        this.singleSession = singleSession;
    }

}