001 /**
002 *
003 * Copyright 2004 Protique Ltd
004 *
005 * Licensed under the Apache License, Version 2.0 (the "License");
006 * you may not use this file except in compliance with the License.
007 * 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 org.activemq.advisories;
020
021 import java.util.Iterator;
022 import java.util.List;
023 import java.util.Map;
024 import java.util.Set;
025 import javax.jms.Connection;
026 import javax.jms.Destination;
027 import javax.jms.JMSException;
028 import javax.jms.Message;
029 import javax.jms.MessageConsumer;
030 import javax.jms.MessageListener;
031 import javax.jms.ObjectMessage;
032 import javax.jms.Session;
033 import org.apache.commons.logging.Log;
034 import org.apache.commons.logging.LogFactory;
035 import org.activemq.message.ActiveMQDestination;
036 import org.activemq.message.ProducerInfo;
037 import EDU.oswego.cs.dl.util.concurrent.ConcurrentHashMap;
038 import EDU.oswego.cs.dl.util.concurrent.CopyOnWriteArrayList;
039 import EDU.oswego.cs.dl.util.concurrent.CopyOnWriteArraySet;
040 import EDU.oswego.cs.dl.util.concurrent.SynchronizedBoolean;
041 /**
042 * A helper class for listening for MessageProducer advisories
043 *
044 * * @version $Revision: 1.1.1.1 $
045 */
046
047 public class ProducerAdvisor implements MessageListener {
048 private static final Log log = LogFactory.getLog(ProducerAdvisor.class);
049 private Connection connection;
050 private ActiveMQDestination destination;
051 private Session session;
052 private List listeners = new CopyOnWriteArrayList();
053 private SynchronizedBoolean started = new SynchronizedBoolean(false);
054 private Map activeProducers = new ConcurrentHashMap();
055
056 /**
057 * Construct a ProducerAdvisor
058 * @param connection
059 * @param destination the destination to listen for Producer events
060 * @throws JMSException
061 */
062 public ProducerAdvisor(Connection connection, Destination destination) throws JMSException{
063 this.connection = connection;
064 this.destination = ActiveMQDestination.transformDestination(destination);
065 }
066
067 /**
068 * start listening for advisories
069 * @throws JMSException
070 *
071 */
072 public void start() throws JMSException {
073 if (started.commit(false, true)) {
074 session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
075 MessageConsumer consumer = session.createConsumer(destination.getTopicForProducerAdvisory());
076 consumer.setMessageListener(this);
077 }
078 }
079
080 /**
081 * stop listening for advisories
082 * @throws JMSException
083 */
084 public void stop() throws JMSException{
085 if (started.commit(true,false)){
086 if (session != null){
087 session.close();
088 }
089 }
090 }
091
092 /**
093 * Add a listener
094 * @param l
095 */
096 public void addListener(ProducerAdvisoryEventListener l){
097 listeners.add(l);
098 }
099
100 /**
101 * Remove a listener
102 * @param l
103 */
104 public void removeListener(ProducerAdvisoryEventListener l){
105 listeners.remove(l);
106 }
107
108
109 /**
110 * returns true if there is an active producer for the destination
111 *
112 * @param destination
113 * @return true if a producer for the destination
114 */
115 public boolean isActive(Destination destination) {
116 return activeProducers.containsKey(destination);
117 }
118
119 /**
120 * return a set of active ProducerInfo's for a particular destination
121 * @param destination
122 * @return the set of ProducerInfo objects currently active
123 */
124 public Set activeProducers(Destination destination) {
125 Set set = (Set) activeProducers.get(destination);
126 return set != null ? set : new CopyOnWriteArraySet();
127 }
128
129
130
131
132 /**
133 * OnMessage() implementation
134 * @param msg
135 */
136 public void onMessage(Message msg){
137 if (msg instanceof ObjectMessage){
138 try {
139 ProducerInfo info = (ProducerInfo)((ObjectMessage)msg).getObject();
140 updateActiveProducers(info);
141 ProducerAdvisoryEvent event = new ProducerAdvisoryEvent(info);
142 fireEvent(event);
143 }
144 catch (JMSException e) {
145 log.error("Failed to process message: " + msg);
146 }
147 }
148 }
149
150 private void fireEvent(ProducerAdvisoryEvent event){
151 for (Iterator i = listeners.iterator(); i.hasNext(); ){
152 ProducerAdvisoryEventListener l = (ProducerAdvisoryEventListener)i.next();
153 l.onEvent(event);
154 }
155 }
156
157 private void updateActiveProducers(ProducerInfo info) {
158 Set set = (Set) activeProducers.get(info.getDestination());
159 if (info.isStarted()) {
160 if (set == null) {
161 set = new CopyOnWriteArraySet();
162 activeProducers.put(info.getDestination(), set);
163 }
164 set.add(info);
165 }
166 else {
167 if (set != null) {
168 set.remove(info);
169 if (set.isEmpty()) {
170 activeProducers.remove(set);
171 }
172 }
173 }
174 }
175
176
177 }