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.Iterator;
021    import java.util.LinkedHashMap;
022    import java.util.Map;
023    
024    import org.apache.camel.Exchange;
025    import org.apache.camel.Expression;
026    
027    /**
028     * A {@link Collection} which aggregates exchanges together using a correlation
029     * expression so that there is only a single message exchange sent for a single
030     * correlation key.
031     * 
032     * @version $Revision: 1.1 $
033     */
034    public class AggregationCollection extends AbstractCollection<Exchange> {
035        private final Expression<Exchange> correlationExpression;
036        private final AggregationStrategy aggregationStrategy;
037        private Map<Object, Exchange> map = new LinkedHashMap<Object, Exchange>();
038    
039        public AggregationCollection(Expression<Exchange> correlationExpression,
040                                     AggregationStrategy aggregationStrategy) {
041            this.correlationExpression = correlationExpression;
042            this.aggregationStrategy = aggregationStrategy;
043        }
044    
045        @Override
046        public boolean add(Exchange exchange) {
047            Object correlationKey = correlationExpression.evaluate(exchange);
048            Exchange oldExchange = map.get(correlationKey);
049            Exchange newExchange = exchange;
050            if (oldExchange != null) {
051                newExchange = aggregationStrategy.aggregate(oldExchange, newExchange);
052            }
053    
054            // the strategy may just update the old exchange and return it
055            if (newExchange != oldExchange) {
056                map.put(correlationKey, newExchange);
057            }
058            return true;
059        }
060    
061        public Iterator<Exchange> iterator() {
062            return map.values().iterator();
063        }
064    
065        public int size() {
066            return map.size();
067        }
068    }