001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018 package listeners;
019
020
021 import javax.servlet.ServletContext;
022 import javax.servlet.ServletContextEvent;
023 import javax.servlet.ServletContextListener;
024 import javax.servlet.http.HttpSessionAttributeListener;
025 import javax.servlet.http.HttpSessionBindingEvent;
026 import javax.servlet.http.HttpSessionEvent;
027 import javax.servlet.http.HttpSessionListener;
028
029
030 /**
031 * Example listener for context-related application events, which were
032 * introduced in the 2.3 version of the Servlet API. This listener
033 * merely documents the occurrence of such events in the application log
034 * associated with our servlet context.
035 *
036 * @author Craig R. McClanahan
037 * @version $Revision: 664175 $ $Date: 2008-06-06 18:43:44 -0400 (Fri, 06 Jun 2008) $
038 */
039
040 public final class SessionListener
041 implements ServletContextListener,
042 HttpSessionAttributeListener, HttpSessionListener {
043
044 // ----------------------------------------------------- Instance Variables
045
046
047 /**
048 * The servlet context with which we are associated.
049 */
050 private ServletContext context = null;
051
052 // --------------------------------------------------------- Public Methods
053
054
055 /**
056 * Record the fact that a servlet context attribute was added.
057 *
058 * @param event The session attribute event
059 */
060 public void attributeAdded(HttpSessionBindingEvent event) {
061
062 log("attributeAdded('" + event.getSession().getId() + "', '" +
063 event.getName() + "', '" + event.getValue() + "')");
064
065 }
066
067
068 /**
069 * Record the fact that a servlet context attribute was removed.
070 *
071 * @param event The session attribute event
072 */
073 public void attributeRemoved(HttpSessionBindingEvent event) {
074
075 log("attributeRemoved('" + event.getSession().getId() + "', '" +
076 event.getName() + "', '" + event.getValue() + "')");
077
078 }
079
080
081 /**
082 * Record the fact that a servlet context attribute was replaced.
083 *
084 * @param event The session attribute event
085 */
086 public void attributeReplaced(HttpSessionBindingEvent event) {
087
088 log("attributeReplaced('" + event.getSession().getId() + "', '" +
089 event.getName() + "', '" + event.getValue() + "')");
090
091 }
092
093
094 /**
095 * Record the fact that this web application has been destroyed.
096 *
097 * @param event The servlet context event
098 */
099 public void contextDestroyed(ServletContextEvent event) {
100
101 log("contextDestroyed()");
102 this.context = null;
103
104 }
105
106
107 /**
108 * Record the fact that this web application has been initialized.
109 *
110 * @param event The servlet context event
111 */
112 public void contextInitialized(ServletContextEvent event) {
113
114 this.context = event.getServletContext();
115 log("contextInitialized()");
116
117 }
118
119
120 /**
121 * Record the fact that a session has been created.
122 *
123 * @param event The session event
124 */
125 public void sessionCreated(HttpSessionEvent event) {
126
127 log("sessionCreated('" + event.getSession().getId() + "')");
128
129 }
130
131
132 /**
133 * Record the fact that a session has been destroyed.
134 *
135 * @param event The session event
136 */
137 public void sessionDestroyed(HttpSessionEvent event) {
138
139 log("sessionDestroyed('" + event.getSession().getId() + "')");
140
141 }
142
143 // -------------------------------------------------------- Private Methods
144
145
146 /**
147 * Log a message to the servlet context application log.
148 *
149 * @param message Message to be logged
150 */
151 private void log(String message) {
152
153 if (context != null)
154 context.log("SessionListener: " + message);
155 else
156 System.out.println("SessionListener: " + message);
157
158 }
159
160
161 /**
162 * Log a message and associated exception to the servlet context
163 * application log.
164 *
165 * @param message Message to be logged
166 * @param throwable Exception to be logged
167 */
168 private void log(String message, Throwable throwable) {
169
170 if (context != null)
171 context.log("SessionListener: " + message, throwable);
172 else {
173 System.out.println("SessionListener: " + message);
174 throwable.printStackTrace(System.out);
175 }
176
177 }
178
179
180 }