/*
 *  Copyright 2008 biaoping.yin
 *
 *  Licensed under the Apache 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.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package org.frameworkset.web.servlet.mvc;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import javax.servlet.jsp.PageContext;

import org.frameworkset.web.servlet.Controller;
import org.frameworkset.web.servlet.ModelAndView;
import org.frameworkset.web.servlet.support.WebContentGenerator;
import org.frameworkset.web.util.WebUtils;

/**
 * <p>Title: AbstractController.java</p> 
 * <p>Description: </p>
 * <p>bboss workgroup</p>
 * <p>Copyright (c) 2008</p>
 * @Date 2010-10-6
 * @author biaoping.yin
 * @version 1.0
 */
public abstract class AbstractController  extends WebContentGenerator implements Controller{

	private boolean synchronizeOnSession = false;
	
	


	/**
	 * Set if controller execution should be synchronized on the session,
	 * to serialize parallel invocations from the same client.
	 * <p>More specifically, the execution of the <code>handleRequestInternal</code>
	 * method will get synchronized if this flag is "true". The best available
	 * session mutex will be used for the synchronization; ideally, this will
	 * be a mutex exposed by HttpSessionMutexListener.
	 * <p>The session mutex is guaranteed to be the same object during
	 * the entire lifetime of the session, available under the key defined
	 * by the <code>SESSION_MUTEX_ATTRIBUTE</code> constant. It serves as a
	 * safe reference to synchronize on for locking on the current session.
	 * <p>In many cases, the HttpSession reference itself is a safe mutex
	 * as well, since it will always be the same object reference for the
	 * same active logical session. However, this is not guaranteed across
	 * different servlet containers; the only 100% safe way is a session mutex.

	 */
	public final void setSynchronizeOnSession(boolean synchronizeOnSession) {
		this.synchronizeOnSession = synchronizeOnSession;
	}

	/**
	 * Return whether controller execution should be synchronized on the session.
	 */
	public final boolean isSynchronizeOnSession() {
		return this.synchronizeOnSession;
	}


	public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response,PageContext pageContext)
			throws Exception {

		// Delegate to WebContentGenerator for checking and preparing.
		checkAndPrepare(request, response, this instanceof LastModified);

		// Execute handleRequestInternal in synchronized block if required.
		if (this.synchronizeOnSession) {
			HttpSession session = request.getSession(false);
			if (session != null) {
				Object mutex = WebUtils.getSessionMutex(session);
				synchronized (mutex) {
					return handleRequestInternal(request, response,pageContext);
				}
			}
		}
		
		return handleRequestInternal(request, response,pageContext);
	}

	/**
	 * Template method. Subclasses must implement this.
	 * The contract is the same as for <code>handleRequest</code>.
	 * @see #handleRequest
	 */
	protected abstract ModelAndView handleRequestInternal(HttpServletRequest request, HttpServletResponse response,PageContext pageContext)
	    throws Exception;

}