001 /** 002 * 003 * Licensed to the Apache Software Foundation (ASF) under one or more 004 * contributor license agreements. See the NOTICE file distributed with 005 * this work for additional information regarding copyright ownership. 006 * The ASF licenses this file to You under the Apache License, Version 2.0 007 * (the "License"); you may not use this file except in compliance with 008 * the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, software 013 * distributed under the License is distributed on an "AS IS" BASIS, 014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 015 * See the License for the specific language governing permissions and 016 * limitations under the License. 017 */ 018 package org.apache.camel.processor.idempotent; 019 020 import org.apache.camel.Exchange; 021 import org.apache.camel.Expression; 022 import org.apache.camel.Processor; 023 import org.apache.camel.impl.ServiceSupport; 024 import org.apache.camel.util.ExpressionHelper; 025 import org.apache.camel.util.ServiceHelper; 026 import org.apache.commons.logging.Log; 027 import org.apache.commons.logging.LogFactory; 028 029 /** 030 * An implementation of the 031 * <a href="http://activemq.apache.org/camel/idempotent-consumer.html">Idempotent Consumer</a> pattern. 032 * 033 * @version $Revision: 1.1 $ 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, MessageIdRepository messageIdRepository, Processor nextProcessor) { 042 this.messageIdExpression = messageIdExpression; 043 this.messageIdRepository = messageIdRepository; 044 this.nextProcessor = nextProcessor; 045 } 046 047 @Override 048 public String toString() { 049 return "IdempotentConsumer[expression=" + messageIdExpression + ", repository=" + messageIdRepository + ", processor=" + nextProcessor + "]"; 050 } 051 052 public void process(Exchange exchange) throws Exception { 053 String messageId = ExpressionHelper.evaluateAsString(messageIdExpression, exchange); 054 if (messageId == null) { 055 throw new NoMessageIdException(exchange, messageIdExpression); 056 } 057 if (!messageIdRepository.contains(messageId)) { 058 nextProcessor.process(exchange); 059 } 060 else { 061 onDuplicateMessage(exchange, messageId); 062 } 063 } 064 065 // Properties 066 //------------------------------------------------------------------------- 067 public Expression<Exchange> getMessageIdExpression() { 068 return messageIdExpression; 069 } 070 071 public MessageIdRepository getMessageIdRepository() { 072 return messageIdRepository; 073 } 074 075 public Processor getNextProcessor() { 076 return nextProcessor; 077 } 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 processing a duplicate message 093 * 094 * @param exchange the exchange 095 * @param messageId the message ID of this exchange 096 */ 097 protected void onDuplicateMessage(Exchange exchange, String messageId) { 098 if (log.isDebugEnabled()) { 099 log.debug("Ignoring duplicate message with id: " + messageId + " for exchange: " + exchange); 100 } 101 } 102 }