001 /*
002 * Copyright 2004 The Apache Software Foundation
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 * http://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
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: 267129 $ $Date: 2004-03-18 08:40:35 -0800 (Thu, 18 Mar 2004) $
038 */
039
040 public final class SessionListener
041 implements ServletContextListener,
042 HttpSessionAttributeListener, HttpSessionListener {
043
044
045 // ----------------------------------------------------- Instance Variables
046
047
048 /**
049 * The servlet context with which we are associated.
050 */
051 private ServletContext context = null;
052
053
054 // --------------------------------------------------------- Public Methods
055
056
057 /**
058 * Record the fact that a servlet context attribute was added.
059 *
060 * @param event The session attribute event
061 */
062 public void attributeAdded(HttpSessionBindingEvent event) {
063
064 log("attributeAdded('" + event.getSession().getId() + "', '" +
065 event.getName() + "', '" + event.getValue() + "')");
066
067 }
068
069
070 /**
071 * Record the fact that a servlet context attribute was removed.
072 *
073 * @param event The session attribute event
074 */
075 public void attributeRemoved(HttpSessionBindingEvent event) {
076
077 log("attributeRemoved('" + event.getSession().getId() + "', '" +
078 event.getName() + "', '" + event.getValue() + "')");
079
080 }
081
082
083 /**
084 * Record the fact that a servlet context attribute was replaced.
085 *
086 * @param event The session attribute event
087 */
088 public void attributeReplaced(HttpSessionBindingEvent event) {
089
090 log("attributeReplaced('" + event.getSession().getId() + "', '" +
091 event.getName() + "', '" + event.getValue() + "')");
092
093 }
094
095
096 /**
097 * Record the fact that this web application has been destroyed.
098 *
099 * @param event The servlet context event
100 */
101 public void contextDestroyed(ServletContextEvent event) {
102
103 log("contextDestroyed()");
104 this.context = null;
105
106 }
107
108
109 /**
110 * Record the fact that this web application has been initialized.
111 *
112 * @param event The servlet context event
113 */
114 public void contextInitialized(ServletContextEvent event) {
115
116 this.context = event.getServletContext();
117 log("contextInitialized()");
118
119 }
120
121
122 /**
123 * Record the fact that a session has been created.
124 *
125 * @param event The session event
126 */
127 public void sessionCreated(HttpSessionEvent event) {
128
129 log("sessionCreated('" + event.getSession().getId() + "')");
130
131 }
132
133
134 /**
135 * Record the fact that a session has been destroyed.
136 *
137 * @param event The session event
138 */
139 public void sessionDestroyed(HttpSessionEvent event) {
140
141 log("sessionDestroyed('" + event.getSession().getId() + "')");
142
143 }
144
145
146 // -------------------------------------------------------- Private Methods
147
148
149 /**
150 * Log a message to the servlet context application log.
151 *
152 * @param message Message to be logged
153 */
154 private void log(String message) {
155
156 if (context != null)
157 context.log("SessionListener: " + message);
158 else
159 System.out.println("SessionListener: " + message);
160
161 }
162
163
164 /**
165 * Log a message and associated exception to the servlet context
166 * application log.
167 *
168 * @param message Message to be logged
169 * @param throwable Exception to be logged
170 */
171 private void log(String message, Throwable throwable) {
172
173 if (context != null)
174 context.log("SessionListener: " + message, throwable);
175 else {
176 System.out.println("SessionListener: " + message);
177 throwable.printStackTrace(System.out);
178 }
179
180 }
181
182
183 }