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
19 package listeners;
20
21
22 import javax.servlet.ServletContext;
23 import javax.servlet.ServletContextAttributeEvent;
24 import javax.servlet.ServletContextAttributeListener;
25 import javax.servlet.ServletContextEvent;
26 import javax.servlet.ServletContextListener;
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: 664175 $ $Date: 2008-06-06 18:43:44 -0400 (Fri, 06 Jun 2008) $
37 */
38
39 public final class ContextListener
40 implements ServletContextAttributeListener, ServletContextListener {
41
42 // ----------------------------------------------------- Instance Variables
43
44
45 /**
46 * The servlet context with which we are associated.
47 */
48 private ServletContext context = null;
49
50 // --------------------------------------------------------- Public Methods
51
52
53 /**
54 * Record the fact that a servlet context attribute was added.
55 *
56 * @param event The servlet context attribute event
57 */
58 public void attributeAdded(ServletContextAttributeEvent event) {
59
60 log("attributeAdded('" + event.getName() + "', '" +
61 event.getValue() + "')");
62
63 }
64
65
66 /**
67 * Record the fact that a servlet context attribute was removed.
68 *
69 * @param event The servlet context attribute event
70 */
71 public void attributeRemoved(ServletContextAttributeEvent event) {
72
73 log("attributeRemoved('" + event.getName() + "', '" +
74 event.getValue() + "')");
75
76 }
77
78
79 /**
80 * Record the fact that a servlet context attribute was replaced.
81 *
82 * @param event The servlet context attribute event
83 */
84 public void attributeReplaced(ServletContextAttributeEvent event) {
85
86 log("attributeReplaced('" + event.getName() + "', '" +
87 event.getValue() + "')");
88
89 }
90
91
92 /**
93 * Record the fact that this web application has been destroyed.
94 *
95 * @param event The servlet context event
96 */
97 public void contextDestroyed(ServletContextEvent event) {
98
99 log("contextDestroyed()");
100 this.context = null;
101
102 }
103
104
105 /**
106 * Record the fact that this web application has been initialized.
107 *
108 * @param event The servlet context event
109 */
110 public void contextInitialized(ServletContextEvent event) {
111
112 this.context = event.getServletContext();
113 log("contextInitialized()");
114
115 }
116
117 // -------------------------------------------------------- Private Methods
118
119
120 /**
121 * Log a message to the servlet context application log.
122 *
123 * @param message Message to be logged
124 */
125 private void log(String message) {
126
127 if (context != null)
128 context.log("ContextListener: " + message);
129 else
130 System.out.println("ContextListener: " + message);
131
132 }
133
134
135 /**
136 * Log a message and associated exception to the servlet context
137 * application log.
138 *
139 * @param message Message to be logged
140 * @param throwable Exception to be logged
141 */
142 private void log(String message, Throwable throwable) {
143
144 if (context != null)
145 context.log("ContextListener: " + message, throwable);
146 else {
147 System.out.println("ContextListener: " + message);
148 throwable.printStackTrace(System.out);
149 }
150
151 }
152
153
154 }