org.sakaiproject.tool.assessment.ui.web.session.SessionUtil.java Source code

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 * Copyright (c) 2004, 2005, 2006, 2008, 2009 The Sakai Foundation
 *
 * Licensed under the Educational Community License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *       http://www.opensource.org/licenses/ECL-2.0
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package org.sakaiproject.tool.assessment.ui.web.session;

import javax.faces.context.ExternalContext;
import javax.faces.context.FacesContext;
import javax.servlet.http.HttpSession;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.sakaiproject.tool.api.ToolSession;
import org.sakaiproject.tool.cover.SessionManager;
import org.sakaiproject.tool.assessment.ui.bean.delivery.DeliveryBean;
import org.sakaiproject.tool.assessment.integration.context.IntegrationContextFactory;

/**
 * <p>
 * <code>SessionUtil</code> provides a mechanism to assign the inactive
 * interval for the current session. In the event that user has more than one
 * thread accessing the same or separate assessments, <code> SessionUtil </code>
 * guarantees that the session will have the (maximum assessment time limit among threads)
 * as the value of the inactive interval.
 *
 * <pre>
 *   <tt>Scenarios which require a greater inactive interval than the default interval:
 *     - Assessments or surveys which are delivered on a single page
 *     - Questions which require more time than the default application timeout setting
 *   </tt>
 * </pre>
 *
 *
 * @author  Jarrod Lannan
 * @version $Revision$
 * @see     javax.servlet.http.HttpSession
 * @see     javax.servlet.http.HttpSession#setMaxInactiveInterval(int)
 *
 */
public class SessionUtil {

    public static final String EXTERNAL_APP_INTERVAL = "app_interval_val";
    public static final int HOURS_TO_SECONDS_MULTIPLIER = 60 * 60;
    public static final int MINUTES_TO_SECONDS_MULTIPLIER = 60;
    public static final int DEFAULT_APP_INTERVAL_VAL = 5 * HOURS_TO_SECONDS_MULTIPLIER;

    private static final int INTERVAL_BUFFER = 60 * 15;
    private static Log log = LogFactory.getLog(SessionUtil.class);

    /**
     * Sets the current <code>HttpSession</code> maxInactiveInterval value
     * @param context the faces context
     * @param delivery the delivery bean
     * @param beginAssessment true if called from the beginning of an assessment, otherwise false
     *
     * @see org.sakaiproject.tool.assessment.ui.bean.delivery.DeliveryBean
     */
    public static void setSessionTimeout(FacesContext context, DeliveryBean delivery, boolean beginAssessment) {
        if (!IntegrationContextFactory.getInstance().isIntegrated()) {
            return;
        }

        ExternalContext exContext = context.getExternalContext();
        HttpSession session = (HttpSession) exContext.getSession(false);

        if (session == null) {
            return;
        }

        /** if we have a tool session then get big session (MySession) */
        if (session instanceof ToolSession) {
            session = (HttpSession) SessionManager.getCurrentSession();
        }

        synchronized (session) {

            if (beginAssessment) {

                /**
                 * if we have not already set value
                 * (ensure setSessionTimeout is called only once at beginning of assessment)
                 */
                int interval = DEFAULT_APP_INTERVAL_VAL;
                if (session.getAttribute(EXTERNAL_APP_INTERVAL) == null) {
                    if (delivery != null && delivery.getHasTimeLimit()) {
                        interval = delivery.getTimeLimit_hour() * HOURS_TO_SECONDS_MULTIPLIER;
                        interval += delivery.getTimeLimit_minute() * MINUTES_TO_SECONDS_MULTIPLIER;
                    } else {
                        /** for assessments without time limit */
                        interval = DEFAULT_APP_INTERVAL_VAL;
                    }
                }

                if (interval > session.getMaxInactiveInterval()) {
                    if (log.isDebugEnabled()) {
                        log.debug("begin_assessment: Setting session " + session.getId() + " inactive interval= "
                                + interval + " seconds");
                    }
                    /** store current interval value */
                    session.setAttribute(EXTERNAL_APP_INTERVAL, Integer.valueOf(session.getMaxInactiveInterval()));
                    session.setMaxInactiveInterval(interval + INTERVAL_BUFFER);
                }
            } else { /** on assessment submission or 'save and exit' from assessment */
                Integer returnVal = (Integer) session.getAttribute(EXTERNAL_APP_INTERVAL);
                if (returnVal == null) {
                    return;
                } else {
                    session.removeAttribute(EXTERNAL_APP_INTERVAL);
                    if (log.isDebugEnabled()) {
                        log.debug("end_assessment: Setting session " + session.getId() + " inactive interval= "
                                + returnVal + " seconds");
                    }
                    /** set to value of interval before taking */
                    session.setMaxInactiveInterval(returnVal.intValue());
                }
            }
        }
    }
}