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Java > Open Source Codes > org > springframework > web > util > WebAppRootListener


1 /*
2  * Copyright 2002-2005 the original author or authors.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16
17 package org.springframework.web.util;
18
19 import javax.servlet.ServletContextEvent JavaDoc;
20 import javax.servlet.ServletContextListener JavaDoc;
21
22 /**
23  * Listener that sets a system property to the web application root directory.
24  * The key of the system property can be defined with the "webAppRootKey" init
25  * parameter at the servlet context level (i.e. context-param in web.xml),
26  * the default key is "webapp.root".
27  *
28  * <p>Can be used for toolkits that support substition with system properties
29  * (i.e. System.getProperty values), like Log4J's "${key}" syntax within log
30  * file locations.
31  *
32  * <p>Note: This listener should be placed before ContextLoaderListener in web.xml,
33  * at least when used for Log4J. Log4jConfigListener sets the system property
34  * implicitly, so there's no need for this listener in addition to it.
35  *
36  * <p><b>WARNING</b>: Some containers like Tomcat do NOT keep system properties separate
37  * per web app. You have to use unique "webAppRootKey" context-params per web app
38  * then, to avoid clashes. Other containers like Resin do isolate each web app's
39  * system properties: Here you can use the default key (i.e. no "webAppRootKey"
40  * context-param at all) without worrying.
41  *
42  * <p><b>WARNING</b>: The WAR file containing the web application needs to be expanded
43  * to allow for setting the web app root system property. This is by default not
44  * the case when a WAR file gets deployed to WebLogic, for example. Do not use
45  * this listener in such an environment!
46  *
47  * @author Juergen Hoeller
48  * @since 18.04.2003
49  * @see WebUtils#setWebAppRootSystemProperty
50  * @see Log4jConfigListener
51  * @see java.lang.System#getProperty
52  */
53 public class WebAppRootListener implements ServletContextListener JavaDoc {
54
55     public void contextInitialized(ServletContextEvent JavaDoc event) {
56         WebUtils.setWebAppRootSystemProperty(event.getServletContext());
57     }
58
59     public void contextDestroyed(ServletContextEvent JavaDoc event) {
60         WebUtils.removeWebAppRootSystemProperty(event.getServletContext());
61     }
62
63 }
64
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