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Spring Framework example source code file (HttpSessionMutexListener.java)

This example Spring Framework source code file (HttpSessionMutexListener.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Spring Framework tags/keywords

http, httpsessionlistener, httpsessionlistener, httpsessionmutexlistener, httpsessionmutexlistener, io, mutex, mutex, request, response, serializable, serializable, servlet

The Spring Framework HttpSessionMutexListener.java source code

/*
 * Copyright 2002-2007 the original author or authors.
 *
 * 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.springframework.web.util;

import java.io.Serializable;

import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

/**
 * Servlet 2.3 HttpSessionListener that automatically exposes the
 * session mutex when an HttpSession gets created.
 * To be registered as a listener in <code>web.xml.
 *
 * <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 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.
 *
 * @author Juergen Hoeller
 * @since 1.2.7
 * @see WebUtils#SESSION_MUTEX_ATTRIBUTE
 * @see WebUtils#getSessionMutex(javax.servlet.http.HttpSession)
 * @see org.springframework.web.servlet.mvc.AbstractController#setSynchronizeOnSession
 */
public class HttpSessionMutexListener implements HttpSessionListener {

	public void sessionCreated(HttpSessionEvent event) {
		event.getSession().setAttribute(WebUtils.SESSION_MUTEX_ATTRIBUTE, new Mutex());
	}

	public void sessionDestroyed(HttpSessionEvent event) {
		event.getSession().removeAttribute(WebUtils.SESSION_MUTEX_ATTRIBUTE);
	}


	/**
	 * The mutex to be registered.
	 * Doesn't need to be anything but a plain Object to synchronize on.
	 * Should be serializable to allow for HttpSession persistence.
	 */
	private static class Mutex implements Serializable {
	}

}

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