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