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 */ 017package org.apache.camel.processor.aggregate; 018 019import org.apache.camel.Exchange; 020 021import static org.apache.camel.util.ExchangeHelper.hasExceptionBeenHandledByErrorHandler; 022 023/** 024 * An {@link AggregationStrategy} which just uses the latest exchange which is useful 025 * for status messages where old status messages have no real value. Another example is things 026 * like market data prices, where old stock prices are not that relevant, only the current price is. 027 * 028 * @version 029 */ 030public class UseLatestAggregationStrategy implements AggregationStrategy { 031 032 public Exchange aggregate(Exchange oldExchange, Exchange newExchange) { 033 if (newExchange == null) { 034 return oldExchange; 035 } 036 if (oldExchange == null) { 037 return newExchange; 038 } 039 040 Exchange answer = null; 041 042 // propagate exception first 043 propagateException(oldExchange, newExchange); 044 if (newExchange.getException() != null) { 045 answer = newExchange; 046 } 047 048 if (answer == null) { 049 // the propagate failures 050 answer = propagateFailure(oldExchange, newExchange); 051 } 052 053 return answer; 054 } 055 056 protected void propagateException(Exchange oldExchange, Exchange newExchange) { 057 if (oldExchange == null) { 058 return; 059 } 060 061 // propagate exception from old exchange if there isn't already an exception 062 if (newExchange.getException() == null) { 063 newExchange.setException(oldExchange.getException()); 064 newExchange.setProperty(Exchange.FAILURE_ENDPOINT, oldExchange.getProperty(Exchange.FAILURE_ENDPOINT)); 065 } 066 } 067 068 protected Exchange propagateFailure(Exchange oldExchange, Exchange newExchange) { 069 if (oldExchange == null) { 070 return newExchange; 071 } 072 073 // propagate exception from old exchange if there isn't already an exception 074 boolean exceptionHandled = hasExceptionBeenHandledByErrorHandler(oldExchange); 075 if (oldExchange.isFailed() || oldExchange.isRollbackOnly() || exceptionHandled) { 076 // propagate failure by using old exchange as the answer 077 return oldExchange; 078 } 079 080 return newExchange; 081 } 082 083 @Override 084 public String toString() { 085 return "UseLatestAggregationStrategy"; 086 } 087}