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 org.apache.camel.Exchange;
020    
021    /**
022     * An {@link AggregationStrategy} which just uses the latest exchange which is useful
023     * for status messages where old status messages have no real value. Another example is things
024     * like market data prices, where old stock prices are not that relevant, only the current price is.
025     *
026     * @version $Revision: 885364 $
027     */
028    public class UseLatestAggregationStrategy implements AggregationStrategy {
029    
030        public Exchange aggregate(Exchange oldExchange, Exchange newExchange) {
031            if (newExchange == null) {
032                return oldExchange;
033            }
034            newExchange.setException(checkException(oldExchange, newExchange));
035            return newExchange;
036        }
037        
038        protected Exception checkException(Exchange oldExchange, Exchange newExchange) {
039            if (oldExchange == null) {
040                return newExchange.getException();
041            } else {
042                return (newExchange != null && newExchange.getException() != null)
043                    ? newExchange.getException()
044                    : oldExchange.getException();
045            }
046        }
047    
048        @Override
049        public String toString() {
050            return "UseLatestAggregationStrategy";
051        }
052    }