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1   /*
2   * Copyright 2004 The Apache Software Foundation
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 listeners;
18  
19  
20  import javax.servlet.ServletContext;
21  import javax.servlet.ServletContextEvent;
22  import javax.servlet.ServletContextListener;
23  import javax.servlet.http.HttpSessionAttributeListener;
24  import javax.servlet.http.HttpSessionBindingEvent;
25  import javax.servlet.http.HttpSessionEvent;
26  import javax.servlet.http.HttpSessionListener;
27  
28  
29  /**
30   * Example listener for context-related application events, which were
31   * introduced in the 2.3 version of the Servlet API.  This listener
32   * merely documents the occurrence of such events in the application log
33   * associated with our servlet context.
34   *
35   * @author Craig R. McClanahan
36   * @version $Revision: 267129 $ $Date: 2004-03-18 08:40:35 -0800 (Thu, 18 Mar 2004) $
37   */
38  
39  public final class SessionListener
40      implements ServletContextListener,
41  	       HttpSessionAttributeListener, HttpSessionListener {
42  
43  
44      // ----------------------------------------------------- Instance Variables
45  
46  
47      /**
48       * The servlet context with which we are associated.
49       */
50      private ServletContext context = null;
51  
52  
53      // --------------------------------------------------------- Public Methods
54  
55  
56      /**
57       * Record the fact that a servlet context attribute was added.
58       *
59       * @param event The session attribute event
60       */
61      public void attributeAdded(HttpSessionBindingEvent event) {
62  
63  	log("attributeAdded('" + event.getSession().getId() + "', '" +
64  	    event.getName() + "', '" + event.getValue() + "')");
65  
66      }
67  
68  
69      /**
70       * Record the fact that a servlet context attribute was removed.
71       *
72       * @param event The session attribute event
73       */
74      public void attributeRemoved(HttpSessionBindingEvent event) {
75  
76  	log("attributeRemoved('" + event.getSession().getId() + "', '" +
77  	    event.getName() + "', '" + event.getValue() + "')");
78  
79      }
80  
81  
82      /**
83       * Record the fact that a servlet context attribute was replaced.
84       *
85       * @param event The session attribute event
86       */
87      public void attributeReplaced(HttpSessionBindingEvent event) {
88  
89  	log("attributeReplaced('" + event.getSession().getId() + "', '" +
90  	    event.getName() + "', '" + event.getValue() + "')");
91  
92      }
93  
94  
95      /**
96       * Record the fact that this web application has been destroyed.
97       *
98       * @param event The servlet context event
99       */
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 }