org.jasig.web.util.LRUTrackingModelPasser Maven / Gradle / Ivy

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Portlet and Servlet MVC classes to allow AJAX in a portlet.
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/**
 * Copyright 2007 The JA-SIG Collaborative.  All rights reserved.
 * See license distributed with this file and
 * available online at http://www.uportal.org/license.html
 */
package org.jasig.web.util;

import java.util.Map;

import javax.portlet.ActionRequest;
import javax.portlet.ActionResponse;
import javax.portlet.PortletSession;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.web.portlet.util.PortletUtils;

/**
 * Model passer that uses an {@link LRUMap} in the user's session to track model objects for keys. This approach
 * allows a key to be re-used as long as it remains in the map. Keys are purged in LRU order once the map hits
 * its maximum capacity.
 * 
 * @author Eric Dalquist
 * @version $Revision: 1.1 $
 */
public class LRUTrackingModelPasser implements ModelPasser {
    private static final String MODEL_CACHE_KEY = LRUTrackingModelPasser.class.getName() + ".MODEL_CACHE_KEY";
    
    protected final Log logger = LogFactory.getLog(this.getClass());
    
    private int maxSize = 100;
    

    public int getMaxSize() {
        return this.maxSize;
    }
    /**
     * The maximum size of the key cache per user session. Defaults to 100.
     */
    public void setMaxSize(int maxSize) {
        this.maxSize = maxSize;
    }

    /* (non-Javadoc)
     * @see org.jasig.web.util.ModelPasser#getModelFromPortlet(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse, java.lang.String)
     */
    @SuppressWarnings("unchecked")
    public Map getModelFromPortlet(HttpServletRequest request, HttpServletResponse response, String key) {
        final HttpSession session = request.getSession(false);
        if (session == null) {
            this.logger.debug("No session available, returning null for key '" + key + "'");
            return null;
        }
        
        final Map> modelCache = (Map>)session.getAttribute(MODEL_CACHE_KEY);
        if (modelCache == null) {
            this.logger.debug("No model cache Map in session, returning null for key '" + key + "'");
            return null;
        }

        final Map model = modelCache.get(key);
        if (this.logger.isDebugEnabled()) {
            this.logger.debug("Found model '" + model + "' in HttpSession for key '" + key + "'");
        }

        return model;
    }

    /* (non-Javadoc)
     * @see org.jasig.web.util.ModelPasser#passModelToServlet(javax.portlet.ActionRequest, javax.portlet.ActionResponse, java.lang.String, java.util.Map)
     */
    public void passModelToServlet(ActionRequest request, ActionResponse response, String key, Map model) {
        final PortletSession portletSession = request.getPortletSession();
        
        final Map> modelCache = this.getModelCache(portletSession);
        modelCache.put(key, model);
        
        if (this.logger.isDebugEnabled()) {
            this.logger.debug("Stored model '" + model + "' in cache Map for key '" + key + "'");
        }
    }

    @SuppressWarnings("unchecked")
    protected Map> getModelCache(final PortletSession portletSession) {
        Map> modelCache;
        
        synchronized (PortletUtils.getSessionMutex(portletSession)) {
            modelCache = (Map>)portletSession.getAttribute(MODEL_CACHE_KEY, PortletSession.APPLICATION_SCOPE);
            if (modelCache == null) {
                modelCache = new LoggingLRUMap(this.maxSize);
            }

            //Call set on each access so the container can track session updates for replication
            portletSession.setAttribute(MODEL_CACHE_KEY, modelCache, PortletSession.APPLICATION_SCOPE);
        }
        
        return modelCache;
    }
}