001/*
002 * Copyright 2002-2012 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.web.util;
018
019import javax.servlet.ServletContextEvent;
020import javax.servlet.ServletContextListener;
021
022/**
023 * Listener that sets a system property to the web application root directory.
024 * The key of the system property can be defined with the "webAppRootKey" init
025 * parameter at the servlet context level (i.e. context-param in web.xml),
026 * the default key is "webapp.root".
027 *
028 * <p>Can be used for toolkits that support substitution with system properties
029 * (i.e. System.getProperty values), like log4j's "${key}" syntax within log
030 * file locations.
031 *
032 * <p>Note: This listener should be placed before ContextLoaderListener in {@code web.xml},
033 * at least when used for log4j. Log4jConfigListener sets the system property
034 * implicitly, so there's no need for this listener in addition to it.
035 *
036 * <p><b>WARNING</b>: Some containers, e.g. Tomcat, do NOT keep system properties separate
037 * per web app. You have to use unique "webAppRootKey" context-params per web app
038 * then, to avoid clashes. Other containers like Resin do isolate each web app's
039 * system properties: Here you can use the default key (i.e. no "webAppRootKey"
040 * context-param at all) without worrying.
041 *
042 * <p><b>WARNING</b>: The WAR file containing the web application needs to be expanded
043 * to allow for setting the web app root system property. This is by default not
044 * the case when a WAR file gets deployed to WebLogic, for example. Do not use
045 * this listener in such an environment!
046 *
047 * @author Juergen Hoeller
048 * @since 18.04.2003
049 * @see WebUtils#setWebAppRootSystemProperty
050 * @see Log4jConfigListener
051 * @see System#getProperty
052 */
053public class WebAppRootListener implements ServletContextListener {
054
055        @Override
056        public void contextInitialized(ServletContextEvent event) {
057                WebUtils.setWebAppRootSystemProperty(event.getServletContext());
058        }
059
060        @Override
061        public void contextDestroyed(ServletContextEvent event) {
062                WebUtils.removeWebAppRootSystemProperty(event.getServletContext());
063        }
064
065}