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 package org.apache.camel.processor.idempotent;
018
019 import org.apache.camel.Exchange;
020 import org.apache.camel.Expression;
021 import org.apache.camel.Processor;
022 import org.apache.camel.impl.ServiceSupport;
023 import org.apache.camel.util.ExpressionHelper;
024 import org.apache.camel.util.ServiceHelper;
025 import org.apache.commons.logging.Log;
026 import org.apache.commons.logging.LogFactory;
027
028 /**
029 * An implementation of the <a
030 * href="http://activemq.apache.org/camel/idempotent-consumer.html">Idempotent
031 * Consumer</a> pattern.
032 *
033 * @version $Revision: 630568 $
034 */
035 public class IdempotentConsumer extends ServiceSupport implements Processor {
036 private static final transient Log LOG = LogFactory.getLog(IdempotentConsumer.class);
037 private Expression<Exchange> messageIdExpression;
038 private Processor nextProcessor;
039 private MessageIdRepository messageIdRepository;
040
041 public IdempotentConsumer(Expression<Exchange> messageIdExpression,
042 MessageIdRepository messageIdRepository, Processor nextProcessor) {
043 this.messageIdExpression = messageIdExpression;
044 this.messageIdRepository = messageIdRepository;
045 this.nextProcessor = nextProcessor;
046 }
047
048 @Override
049 public String toString() {
050 return "IdempotentConsumer[expression=" + messageIdExpression + ", repository=" + messageIdRepository
051 + ", processor=" + nextProcessor + "]";
052 }
053
054 public void process(Exchange exchange) throws Exception {
055 String messageId = ExpressionHelper.evaluateAsString(messageIdExpression, exchange);
056 if (messageId == null) {
057 throw new NoMessageIdException(exchange, messageIdExpression);
058 }
059 if (!messageIdRepository.contains(messageId)) {
060 nextProcessor.process(exchange);
061 } else {
062 onDuplicateMessage(exchange, messageId);
063 }
064 }
065
066 // Properties
067 // -------------------------------------------------------------------------
068 public Expression<Exchange> getMessageIdExpression() {
069 return messageIdExpression;
070 }
071
072 public MessageIdRepository getMessageIdRepository() {
073 return messageIdRepository;
074 }
075
076 public Processor getNextProcessor() {
077 return nextProcessor;
078 }
079
080 // Implementation methods
081 // -------------------------------------------------------------------------
082
083 protected void doStart() throws Exception {
084 ServiceHelper.startServices(nextProcessor);
085 }
086
087 protected void doStop() throws Exception {
088 ServiceHelper.stopServices(nextProcessor);
089 }
090
091 /**
092 * A strategy method to allow derived classes to overload the behaviour of
093 * processing a duplicate message
094 *
095 * @param exchange the exchange
096 * @param messageId the message ID of this exchange
097 */
098 protected void onDuplicateMessage(Exchange exchange, String messageId) {
099 if (LOG.isDebugEnabled()) {
100 LOG.debug("Ignoring duplicate message with id: " + messageId + " for exchange: " + exchange);
101 }
102 }
103 }