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 package listeners;
019
020
021 import javax.servlet.ServletContext;
022 import javax.servlet.ServletContextAttributeEvent;
023 import javax.servlet.ServletContextAttributeListener;
024 import javax.servlet.ServletContextEvent;
025 import javax.servlet.ServletContextListener;
026
027
028 /**
029 * Example listener for context-related application events, which were
030 * introduced in the 2.3 version of the Servlet API. This listener
031 * merely documents the occurrence of such events in the application log
032 * associated with our servlet context.
033 *
034 * @author Craig R. McClanahan
035 * @version $Revision: 664175 $ $Date: 2008-06-06 18:43:44 -0400 (Fri, 06 Jun 2008) $
036 */
037
038 public final class ContextListener
039 implements ServletContextAttributeListener, ServletContextListener {
040
041 // ----------------------------------------------------- Instance Variables
042
043
044 /**
045 * The servlet context with which we are associated.
046 */
047 private ServletContext context = null;
048
049 // --------------------------------------------------------- Public Methods
050
051
052 /**
053 * Record the fact that a servlet context attribute was added.
054 *
055 * @param event The servlet context attribute event
056 */
057 public void attributeAdded(ServletContextAttributeEvent event) {
058
059 log("attributeAdded('" + event.getName() + "', '" +
060 event.getValue() + "')");
061
062 }
063
064
065 /**
066 * Record the fact that a servlet context attribute was removed.
067 *
068 * @param event The servlet context attribute event
069 */
070 public void attributeRemoved(ServletContextAttributeEvent event) {
071
072 log("attributeRemoved('" + event.getName() + "', '" +
073 event.getValue() + "')");
074
075 }
076
077
078 /**
079 * Record the fact that a servlet context attribute was replaced.
080 *
081 * @param event The servlet context attribute event
082 */
083 public void attributeReplaced(ServletContextAttributeEvent event) {
084
085 log("attributeReplaced('" + event.getName() + "', '" +
086 event.getValue() + "')");
087
088 }
089
090
091 /**
092 * Record the fact that this web application has been destroyed.
093 *
094 * @param event The servlet context event
095 */
096 public void contextDestroyed(ServletContextEvent event) {
097
098 log("contextDestroyed()");
099 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 }