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 package listeners;
018
019
020 import javax.servlet.ServletContext;
021 import javax.servlet.ServletContextEvent;
022 import javax.servlet.ServletContextListener;
023 import javax.servlet.http.HttpSessionAttributeListener;
024 import javax.servlet.http.HttpSessionBindingEvent;
025 import javax.servlet.http.HttpSessionEvent;
026 import javax.servlet.http.HttpSessionListener;
027
028
029 /**
030 * Example listener for context-related application events, which were
031 * introduced in the 2.3 version of the Servlet API. This listener
032 * merely documents the occurrence of such events in the application log
033 * associated with our servlet context.
034 *
035 * @author Craig R. McClanahan
036 * @version $Revision: 267129 $ $Date: 2004-03-18 08:40:35 -0800 (Thu, 18 Mar 2004) $
037 */
038
039 public final class SessionListener
040 implements ServletContextListener,
041 HttpSessionAttributeListener, HttpSessionListener {
042
043
044 // ----------------------------------------------------- Instance Variables
045
046
047 /**
048 * The servlet context with which we are associated.
049 */
050 private ServletContext context = null;
051
052
053 // --------------------------------------------------------- Public Methods
054
055
056 /**
057 * Record the fact that a servlet context attribute was added.
058 *
059 * @param event The session attribute event
060 */
061 public void attributeAdded(HttpSessionBindingEvent event) {
062
063 log("attributeAdded('" + event.getSession().getId() + "', '" +
064 event.getName() + "', '" + event.getValue() + "')");
065
066 }
067
068
069 /**
070 * Record the fact that a servlet context attribute was removed.
071 *
072 * @param event The session attribute event
073 */
074 public void attributeRemoved(HttpSessionBindingEvent event) {
075
076 log("attributeRemoved('" + event.getSession().getId() + "', '" +
077 event.getName() + "', '" + event.getValue() + "')");
078
079 }
080
081
082 /**
083 * Record the fact that a servlet context attribute was replaced.
084 *
085 * @param event The session attribute event
086 */
087 public void attributeReplaced(HttpSessionBindingEvent event) {
088
089 log("attributeReplaced('" + event.getSession().getId() + "', '" +
090 event.getName() + "', '" + event.getValue() + "')");
091
092 }
093
094
095 /**
096 * Record the fact that this web application has been destroyed.
097 *
098 * @param event The servlet context event
099 */
100 public void contextDestroyed(ServletContextEvent event) {
101
102 log("contextDestroyed()");
103 this.context = null;
104
105 }
106
107
108 /**
109 * Record the fact that this web application has been initialized.
110 *
111 * @param event The servlet context event
112 */
113 public void contextInitialized(ServletContextEvent event) {
114
115 this.context = event.getServletContext();
116 log("contextInitialized()");
117
118 }
119
120
121 /**
122 * Record the fact that a session has been created.
123 *
124 * @param event The session event
125 */
126 public void sessionCreated(HttpSessionEvent event) {
127
128 log("sessionCreated('" + event.getSession().getId() + "')");
129
130 }
131
132
133 /**
134 * Record the fact that a session has been destroyed.
135 *
136 * @param event The session event
137 */
138 public void sessionDestroyed(HttpSessionEvent event) {
139
140 log("sessionDestroyed('" + event.getSession().getId() + "')");
141
142 }
143
144
145 // -------------------------------------------------------- Private Methods
146
147
148 /**
149 * Log a message to the servlet context application log.
150 *
151 * @param message Message to be logged
152 */
153 private void log(String message) {
154
155 if (context != null)
156 context.log("SessionListener: " + message);
157 else
158 System.out.println("SessionListener: " + message);
159
160 }
161
162
163 /**
164 * Log a message and associated exception to the servlet context
165 * application log.
166 *
167 * @param message Message to be logged
168 * @param throwable Exception to be logged
169 */
170 private void log(String message, Throwable throwable) {
171
172 if (context != null)
173 context.log("SessionListener: " + message, throwable);
174 else {
175 System.out.println("SessionListener: " + message);
176 throwable.printStackTrace(System.out);
177 }
178
179 }
180
181
182 }