contextlistener.java

的方式呵呵呵呵呵呵呵呵呵呵呵呵呵呵呵分人人人人人人人人人人人人人人人人

/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements.  See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 listeners;


import javax.servlet.ServletContext;
import javax.servlet.ServletContextAttributeEvent;
import javax.servlet.ServletContextAttributeListener;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;


/**
 * Example listener for context-related application events, which were
 * introduced in the 2.3 version of the Servlet API.  This listener
 * merely documents the occurrence of such events in the application log
 * associated with our servlet context.
 *
 * @author Craig R. McClanahan
 * @version $Revision: 500674 $ $Date: 2007-01-28 00:15:00 +0100 (Sun, 28 Jan 2007) $
 */

public final class ContextListener
    implements ServletContextAttributeListener, ServletContextListener {


    // ----------------------------------------------------- Instance Variables


    /**
     * The servlet context with which we are associated.
     */
    private ServletContext context = null;


    // --------------------------------------------------------- Public Methods


    /**
     * Record the fact that a servlet context attribute was added.
     *
     * @param event The servlet context attribute event
     */
    public void attributeAdded(ServletContextAttributeEvent event) {

	log("attributeAdded('" + event.getName() + "', '" +
	    event.getValue() + "')");

    }


    /**
     * Record the fact that a servlet context attribute was removed.
     *
     * @param event The servlet context attribute event
     */
    public void attributeRemoved(ServletContextAttributeEvent event) {

	log("attributeRemoved('" + event.getName() + "', '" +
	    event.getValue() + "')");

    }


    /**
     * Record the fact that a servlet context attribute was replaced.
     *
     * @param event The servlet context attribute event
     */
    public void attributeReplaced(ServletContextAttributeEvent event) {

	log("attributeReplaced('" + event.getName() + "', '" +
	    event.getValue() + "')");

    }


    /**
     * Record the fact that this web application has been destroyed.
     *
     * @param event The servlet context event
     */
    public void contextDestroyed(ServletContextEvent event) {

	log("contextDestroyed()");
	this.context = null;

    }


    /**
     * Record the fact that this web application has been initialized.
     *
     * @param event The servlet context event
     */
    public void contextInitialized(ServletContextEvent event) {

	this.context = event.getServletContext();
	log("contextInitialized()");

    }


    // -------------------------------------------------------- Private Methods


    /**
     * Log a message to the servlet context application log.
     *
     * @param message Message to be logged
     */
    private void log(String message) {

	if (context != null)
	    context.log("ContextListener: " + message);
	else
	    System.out.println("ContextListener: " + message);

    }

}