1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18 package listeners;
19
20
21 import javax.servlet.ServletContext;
22 import javax.servlet.ServletContextAttributeEvent;
23 import javax.servlet.ServletContextAttributeListener;
24 import javax.servlet.ServletContextEvent;
25 import javax.servlet.ServletContextListener;
26
27
28 /**
29 * Example listener for context-related application events, which were
30 * introduced in the 2.3 version of the Servlet API. This listener
31 * merely documents the occurrence of such events in the application log
32 * associated with our servlet context.
33 *
34 * @author Craig R. McClanahan
35 * @version $Revision: 664175 $ $Date: 2008-06-06 18:43:44 -0400 (Fri, 06 Jun 2008) $
36 */
37
38 public final class ContextListener
39 implements ServletContextAttributeListener, ServletContextListener {
40
41 // ----------------------------------------------------- Instance Variables
42
43
44 /**
45 * The servlet context with which we are associated.
46 */
47 private ServletContext context = null;
48
49 // --------------------------------------------------------- Public Methods
50
51
52 /**
53 * Record the fact that a servlet context attribute was added.
54 *
55 * @param event The servlet context attribute event
56 */
57 public void attributeAdded(ServletContextAttributeEvent event) {
58
59 log("attributeAdded('" + event.getName() + "', '" +
60 event.getValue() + "')");
61
62 }
63
64
65 /**
66 * Record the fact that a servlet context attribute was removed.
67 *
68 * @param event The servlet context attribute event
69 */
70 public void attributeRemoved(ServletContextAttributeEvent event) {
71
72 log("attributeRemoved('" + event.getName() + "', '" +
73 event.getValue() + "')");
74
75 }
76
77
78 /**
79 * Record the fact that a servlet context attribute was replaced.
80 *
81 * @param event The servlet context attribute event
82 */
83 public void attributeReplaced(ServletContextAttributeEvent event) {
84
85 log("attributeReplaced('" + event.getName() + "', '" +
86 event.getValue() + "')");
87
88 }
89
90
91 /**
92 * Record the fact that this web application has been destroyed.
93 *
94 * @param event The servlet context event
95 */
96 public void contextDestroyed(ServletContextEvent event) {
97
98 log("contextDestroyed()");
99 this.context = null;
100
101 }
102
103
104 /**
105 * Record the fact that this web application has been initialized.
106 *
107 * @param event The servlet context event
108 */
109 public void contextInitialized(ServletContextEvent event) {
110
111 this.context = event.getServletContext();
112 log("contextInitialized()");
113
114 }
115
116 // -------------------------------------------------------- Private Methods
117
118
119 /**
120 * Log a message to the servlet context application log.
121 *
122 * @param message Message to be logged
123 */
124 private void log(String message) {
125
126 if (context != null)
127 context.log("ContextListener: " + message);
128 else
129 System.out.println("ContextListener: " + message);
130
131 }
132
133
134 /**
135 * Log a message and associated exception to the servlet context
136 * application log.
137 *
138 * @param message Message to be logged
139 * @param throwable Exception to be logged
140 */
141 private void log(String message, Throwable throwable) {
142
143 if (context != null)
144 context.log("ContextListener: " + message, throwable);
145 else {
146 System.out.println("ContextListener: " + message);
147 throwable.printStackTrace(System.out);
148 }
149
150 }
151
152
153 }