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.aggregate;
018
019 import java.util.AbstractCollection;
020 import java.util.Collection;
021 import java.util.Iterator;
022 import java.util.LinkedHashMap;
023 import java.util.Map;
024
025 import org.apache.camel.Exchange;
026 import org.apache.camel.Expression;
027 import org.apache.commons.logging.Log;
028 import org.apache.commons.logging.LogFactory;
029
030 /**
031 * A {@link Collection} which aggregates exchanges together using a correlation
032 * expression so that there is only a single message exchange sent for a single
033 * correlation key.
034 *
035 * @version $Revision: 640438 $
036 */
037 public class AggregationCollection extends AbstractCollection<Exchange> {
038 private static final transient Log LOG = LogFactory.getLog(AggregationCollection.class);
039 private final Expression<Exchange> correlationExpression;
040 private final AggregationStrategy aggregationStrategy;
041 private Map<Object, Exchange> map = new LinkedHashMap<Object, Exchange>();
042
043 public AggregationCollection(Expression<Exchange> correlationExpression,
044 AggregationStrategy aggregationStrategy) {
045 this.correlationExpression = correlationExpression;
046 this.aggregationStrategy = aggregationStrategy;
047 }
048
049 protected Map<Object, Exchange> getMap() {
050 return map;
051 }
052
053 @Override
054 public boolean add(Exchange exchange) {
055 Object correlationKey = correlationExpression.evaluate(exchange);
056 Exchange oldExchange = map.get(correlationKey);
057 Exchange newExchange = exchange;
058 if (oldExchange != null) {
059 newExchange = aggregationStrategy.aggregate(oldExchange, newExchange);
060 }
061
062 // the strategy may just update the old exchange and return it
063 if (newExchange != oldExchange) {
064 LOG.debug("put exchange:" + newExchange + " for key:" + correlationKey);
065 map.put(correlationKey, newExchange);
066 }
067 onAggregation(correlationKey, newExchange);
068 return true;
069 }
070
071 public Iterator<Exchange> iterator() {
072 return map.values().iterator();
073 }
074
075 public int size() {
076 return map.size();
077 }
078
079 @Override
080 public void clear() {
081 map.clear();
082 }
083
084 /**
085 * A strategy method allowing derived classes such as {@link PredicateAggregationCollection}
086 * to check to see if the aggregation has completed
087 */
088 protected void onAggregation(Object correlationKey, Exchange newExchange) {
089 }
090 }