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
019 package listeners;
020
021
022 import javax.servlet.ServletContext;
023 import javax.servlet.ServletContextEvent;
024 import javax.servlet.ServletContextListener;
025 import javax.servlet.http.HttpSessionAttributeListener;
026 import javax.servlet.http.HttpSessionBindingEvent;
027 import javax.servlet.http.HttpSessionEvent;
028 import javax.servlet.http.HttpSessionListener;
029
030
031 /**
032 * Example listener for context-related application events, which were
033 * introduced in the 2.3 version of the Servlet API. This listener
034 * merely documents the occurrence of such events in the application log
035 * associated with our servlet context.
036 *
037 * @author Craig R. McClanahan
038 * @version $Revision: 664175 $ $Date: 2008-06-06 18:43:44 -0400 (Fri, 06 Jun 2008) $
039 */
040
041 public final class SessionListener
042 implements ServletContextListener,
043 HttpSessionAttributeListener, HttpSessionListener {
044
045 // ----------------------------------------------------- Instance Variables
046
047
048 /**
049 * The servlet context with which we are associated.
050 */
051 private ServletContext context = null;
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 // -------------------------------------------------------- Private Methods
145
146
147 /**
148 * Log a message to the servlet context application log.
149 *
150 * @param message Message to be logged
151 */
152 private void log(String message) {
153
154 if (context != null)
155 context.log("SessionListener: " + message);
156 else
157 System.out.println("SessionListener: " + message);
158
159 }
160
161
162 /**
163 * Log a message and associated exception to the servlet context
164 * application log.
165 *
166 * @param message Message to be logged
167 * @param throwable Exception to be logged
168 */
169 private void log(String message, Throwable throwable) {
170
171 if (context != null)
172 context.log("SessionListener: " + message, throwable);
173 else {
174 System.out.println("SessionListener: " + message);
175 throwable.printStackTrace(System.out);
176 }
177
178 }
179
180
181 }