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 org.apache.camel.Endpoint;
020    import org.apache.camel.Expression;
021    import org.apache.camel.Processor;
022    import org.apache.camel.processor.aggregate.AggregationCollection;
023    import org.apache.camel.processor.aggregate.AggregationStrategy;
024    
025    /**
026     * An implementation of the <a
027     * href="http://activemq.apache.org/camel/aggregator.html">Aggregator</a>
028     * pattern where a batch of messages are processed (up to a maximum amount or
029     * until some timeout is reached) and messages for the same correlation key are
030     * combined together using some kind of
031     * {@link AggregationStrategy ) (by default the latest message is used) to compress 
032     * many message exchanges * into a smaller number of exchanges. <p/> A good
033     * example of this is stock market data; you may be receiving 30,000
034     * messages/second and you may want to throttle it right down so that multiple
035     * messages for the same stock are combined (or just the latest message is used
036     * and older prices are discarded). Another idea is to combine line item
037     * messages together into a single invoice message.
038     * 
039     * @version $Revision: 1.1 $
040     * @param correlationExpression the expression used to calculate the correlation
041     *                key. For a JMS message this could be the expression
042     *                <code>header("JMSDestination")</code> or
043     *                <code>header("JMSCorrelationID")</code>
044     */
045    public class Aggregator extends BatchProcessor {
046        public Aggregator(Endpoint endpoint, Processor processor, Expression correlationExpression,
047                          AggregationStrategy aggregationStrategy) {
048            this(endpoint, processor, new AggregationCollection(correlationExpression, aggregationStrategy));
049        }
050    
051        public Aggregator(Endpoint endpoint, Processor processor, AggregationCollection collection) {
052            super(endpoint, processor, collection);
053        }
054    
055        @Override
056        public String toString() {
057            return "Aggregator[to: " + getProcessor() + "]";
058        }
059    }