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;
018
019 import java.util.Collection;
020 import java.util.List;
021
022 import org.apache.camel.Exchange;
023 import org.apache.camel.Processor;
024 import org.apache.camel.Message;
025 import org.apache.commons.logging.Log;
026 import org.apache.commons.logging.LogFactory;
027
028 /**
029 * Creates a Pipeline pattern where the output of the previous step is sent as
030 * input to the next step, reusing the same message exchanges
031 *
032 * @version $Revision: 563931 $
033 */
034 public class Pipeline extends MulticastProcessor implements Processor {
035 private static final transient Log LOG = LogFactory.getLog(Pipeline.class);
036
037 public Pipeline(Collection<Processor> processors) {
038 super(processors);
039 }
040
041 public static Processor newInstance(List<Processor> processors) {
042 if (processors.isEmpty()) {
043 return null;
044 } else if (processors.size() == 1) {
045 return processors.get(0);
046 }
047 return new Pipeline(processors);
048 }
049
050 public void process(Exchange exchange) throws Exception {
051 Exchange nextExchange = exchange;
052 boolean first = true;
053 for (Processor producer : getProcessors()) {
054 if (first) {
055 first = false;
056 } else {
057 nextExchange = createNextExchange(producer, nextExchange);
058 }
059 producer.process(nextExchange);
060 }
061 }
062
063 /**
064 * Strategy method to create the next exchange from the
065 *
066 * @param producer the producer used to send to the endpoint
067 * @param previousExchange the previous exchange
068 * @return a new exchange
069 */
070 protected Exchange createNextExchange(Processor producer, Exchange previousExchange) {
071 Exchange answer = copyExchangeStrategy(previousExchange);
072
073 // now lets set the input of the next exchange to the output of the
074 // previous message if it is not null
075 Object output = previousExchange.getOut().getBody();
076 Message in = answer.getIn();
077 if (output != null) {
078 in.setBody(output);
079 }
080 else {
081 Object previousInBody = previousExchange.getIn().getBody();
082 if (in.getBody() == null && previousInBody != null) {
083 LOG.warn("Bad exchange implementation; the copy() method did not copy across the in body: " + previousExchange
084 + " of type: " + previousExchange.getClass());
085 in.setBody(previousInBody);
086 }
087 }
088 return answer;
089 }
090
091 /**
092 * Strategy method to copy the exchange before sending to another endpoint.
093 * Derived classes such as the {@link Pipeline} will not clone the exchange
094 *
095 * @param exchange
096 * @return the current exchange if no copying is required such as for a
097 * pipeline otherwise a new copy of the exchange is returned.
098 */
099 protected Exchange copyExchangeStrategy(Exchange exchange) {
100 return exchange.copy();
101 }
102
103 @Override
104 public String toString() {
105 return "Pipeline" + getProcessors();
106 }
107 }