/*
 * Copyright 2002-2019 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
 *
 *      https://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.context;

import java.util.Enumeration;

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

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.beans.factory.DisposableBean;

Web application listener that cleans up remaining disposable attributes in the ServletContext, i.e. attributes which implement DisposableBean and haven't been removed before. This is typically used for destroying objects in "application" scope, for which the lifecycle implies destruction at the very end of the web application's shutdown phase. 
Author:
Juergen Hoeller
See Also:
ServletContextScope
ContextLoaderListener
Since:
3.0/**
 * Web application listener that cleans up remaining disposable attributes
 * in the ServletContext, i.e. attributes which implement {@link DisposableBean}
 * and haven't been removed before. This is typically used for destroying objects
 * in "application" scope, for which the lifecycle implies destruction at the
 * very end of the web application's shutdown phase.
 *
 * @author Juergen Hoeller
 * @since 3.0
 * @see org.springframework.web.context.support.ServletContextScope
 * @see ContextLoaderListener
 */
public class ContextCleanupListener implements ServletContextListener {

	private static final Log logger = LogFactory.getLog(ContextCleanupListener.class);


	@Override
	public void contextInitialized(ServletContextEvent event) {
	}

	@Override
	public void contextDestroyed(ServletContextEvent event) {
		cleanupAttributes(event.getServletContext());
	}


	
Find all Spring-internal ServletContext attributes which implement DisposableBean and invoke the destroy method on them. 
Params:
servletContext – the ServletContext to check
See Also:
DisposableBean.destroy()/**
	 * Find all Spring-internal ServletContext attributes which implement
	 * {@link DisposableBean} and invoke the destroy method on them.
	 * @param servletContext the ServletContext to check
	 * @see DisposableBean#destroy()
	 */
	static void cleanupAttributes(ServletContext servletContext) {
		Enumeration<String> attrNames = servletContext.getAttributeNames();
		while (attrNames.hasMoreElements()) {
			String attrName = attrNames.nextElement();
			if (attrName.startsWith("org.springframework.")) {
				Object attrValue = servletContext.getAttribute(attrName);
				if (attrValue instanceof DisposableBean) {
					try {
						((DisposableBean) attrValue).destroy();
					}
					catch (Throwable ex) {
						if (logger.isWarnEnabled()) {
							logger.warn("Invocation of destroy method failed on ServletContext " +
									"attribute with name '" + attrName + "'", ex);
						}
					}
				}
			}
		}
	}

}