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 java.util.ArrayList; 020 import java.util.List; 021 022 import org.apache.camel.Exchange; 023 import org.apache.camel.Expression; 024 import org.apache.camel.Navigate; 025 import org.apache.camel.Processor; 026 import org.apache.camel.impl.ServiceSupport; 027 import org.apache.camel.spi.IdempotentRepository; 028 import org.apache.camel.util.ServiceHelper; 029 import org.apache.commons.logging.Log; 030 import org.apache.commons.logging.LogFactory; 031 032 /** 033 * An implementation of the <a 034 * href="http://camel.apache.org/idempotent-consumer.html">Idempotent Consumer</a> pattern. 035 * 036 * @version $Revision: 782534 $ 037 */ 038 public class IdempotentConsumer extends ServiceSupport implements Processor, Navigate<Processor> { 039 private static final transient Log LOG = LogFactory.getLog(IdempotentConsumer.class); 040 private final Expression messageIdExpression; 041 private final Processor processor; 042 private final IdempotentRepository idempotentRepository; 043 private final boolean eager; 044 045 public IdempotentConsumer(Expression messageIdExpression, IdempotentRepository idempotentRepository, 046 boolean eager, Processor processor) { 047 this.messageIdExpression = messageIdExpression; 048 this.idempotentRepository = idempotentRepository; 049 this.eager = eager; 050 this.processor = processor; 051 } 052 053 @Override 054 public String toString() { 055 return "IdempotentConsumer[" + messageIdExpression + " -> " + processor + "]"; 056 } 057 058 @SuppressWarnings("unchecked") 059 public void process(Exchange exchange) throws Exception { 060 final String messageId = messageIdExpression.evaluate(exchange, String.class); 061 if (messageId == null) { 062 throw new NoMessageIdException(exchange, messageIdExpression); 063 } 064 065 boolean newKey; 066 if (eager) { 067 // add the key to the repository 068 newKey = idempotentRepository.add(messageId); 069 } else { 070 // check if we alrady have the key 071 newKey = !idempotentRepository.contains(messageId); 072 } 073 074 if (!newKey) { 075 // we already have this key so its a duplicate message 076 onDuplicateMessage(exchange, messageId); 077 return; 078 } 079 080 // register our on completion callback 081 exchange.addOnCompletion(new IdempotentOnCompletion(idempotentRepository, messageId, eager)); 082 083 // process the exchange 084 processor.process(exchange); 085 } 086 087 public List<Processor> next() { 088 if (!hasNext()) { 089 return null; 090 } 091 List<Processor> answer = new ArrayList<Processor>(1); 092 answer.add(processor); 093 return answer; 094 } 095 096 public boolean hasNext() { 097 return processor != null; 098 } 099 100 // Properties 101 // ------------------------------------------------------------------------- 102 public Expression getMessageIdExpression() { 103 return messageIdExpression; 104 } 105 106 public IdempotentRepository getIdempotentRepository() { 107 return idempotentRepository; 108 } 109 110 public Processor getProcessor() { 111 return processor; 112 } 113 114 // Implementation methods 115 // ------------------------------------------------------------------------- 116 117 protected void doStart() throws Exception { 118 ServiceHelper.startServices(processor); 119 } 120 121 protected void doStop() throws Exception { 122 ServiceHelper.stopServices(processor); 123 } 124 125 /** 126 * A strategy method to allow derived classes to overload the behaviour of 127 * processing a duplicate message 128 * 129 * @param exchange the exchange 130 * @param messageId the message ID of this exchange 131 */ 132 protected void onDuplicateMessage(Exchange exchange, String messageId) { 133 if (LOG.isDebugEnabled()) { 134 LOG.debug("Ignoring duplicate message with id: " + messageId + " for exchange: " + exchange); 135 } 136 } 137 138 }