/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 * 
 * Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
 * 
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License. You can obtain
 * a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
 * or glassfish/bootstrap/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 * 
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
 * Sun designates this particular file as subject to the "Classpath" exception
 * as provided by Sun in the GPL Version 2 section of the License file that
 * accompanied this code.  If applicable, add the following below the License
 * Header, with the fields enclosed by brackets [] replaced by your own
 * identifying information: "Portions Copyrighted [year]
 * [name of copyright owner]"
 * 
 * Contributor(s):
 * 
 * If you wish your version of this file to be governed by only the CDDL or
 * only the GPL Version 2, indicate your decision by adding "[Contributor]
 * elects to include this software in this distribution under the [CDDL or GPL
 * Version 2] license."  If you don't indicate a single choice of license, a
 * recipient has the option to distribute your version of this file under
 * either the CDDL, the GPL Version 2 or to extend the choice of license to
 * its licensees as provided above.  However, if you add GPL Version 2 code
 * and therefore, elected the GPL Version 2 license, then the option applies
 * only if the new code is made subject to such option by the copyright
 * holder.
 */
 
package com.sun.appserv.web.taglibs.cache;

import javax.servlet.ServletContext;
import javax.servlet.ServletRequest;
import javax.servlet.ServletRequestEvent;
import javax.servlet.ServletRequestListener;

import com.sun.appserv.util.cache.Cache;
import com.sun.appserv.web.cache.CacheManager;

/** 
 * ServletRequestListener which creates a cache for JSP tag body invocations
 * and adds it as a request attribute in response to requestInitialized
 * events, and clears the cache in response to requestDestroyed events.
 */
public class CacheRequestListener implements ServletRequestListener {

    /**
     * No-arg constructor
     */
    public CacheRequestListener() {}


    /** 
     * Receives notification that the request is about to enter the scope
     * of the web application, and adds newly created cache for JSP tag
     * body invocations as a request attribute.
     *
     * @param sre the notification event
     */
    public void requestInitialized(ServletRequestEvent sre) {

        ServletContext context = sre.getServletContext();

        // Check if a cache manager has already been created and set in the
        // context
        CacheManager cm = (CacheManager)
            context.getAttribute(CacheManager.CACHE_MANAGER_ATTR_NAME);

        // Create a new cache manager if one is not present and use it
        // to create a new cache
        if (cm == null) {
            cm = new CacheManager();
        }

        Cache cache = null;
        try {
            cache = cm.createCache();
        } catch (Exception ex) {}

        // Set the cache as a request attribute
        if (cache != null) {
            ServletRequest req = sre.getServletRequest();
            req.setAttribute(Constants.JSPTAG_CACHE_KEY, cache);
        }
    }


    /**
     * Receives notification that the request is about to go out of scope
     * of the web application, and clears the request's cache of JSP tag
     * body invocations (if present).
     *
     * @param sre the notification event
     */
    public void requestDestroyed(ServletRequestEvent sre) {

        // Clear the cache
        ServletRequest req = sre.getServletRequest();
        Cache cache = (Cache) req.getAttribute(Constants.JSPTAG_CACHE_KEY);
        if (cache != null) {
            cache.clear();
        }
    }
}
