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.loadbalancer;
018    
019    import java.util.List;
020    
021    import org.apache.camel.AsyncCallback;
022    import org.apache.camel.Exchange;
023    import org.apache.camel.Processor;
024    
025    /**
026     * A {@link LoadBalancer} implementations which sends to all destinations
027     * (rather like JMS Topics).
028     * <p/>
029     * The {@link org.apache.camel.processor.MulticastProcessor} is more powerful as it offers
030     * option to run in parallel and decide whether or not to stop on failure etc.
031     *
032     * @version 
033     */
034    public class TopicLoadBalancer extends LoadBalancerSupport {
035    
036        public boolean process(final Exchange exchange, final AsyncCallback callback) {
037            List<Processor> list = getProcessors();
038            // too hard to do multiple async, so we do it sync
039            for (Processor processor : list) {
040                try {
041                    Exchange copy = copyExchangeStrategy(processor, exchange);
042                    processor.process(copy);
043                } catch (Throwable e) {
044                    exchange.setException(e);
045                    // stop on failure
046                    break;
047                }
048            }
049            callback.done(true);
050            return true;
051        }
052    
053        /**
054         * Strategy method to copy the exchange before sending to another endpoint.
055         * Derived classes such as the {@link org.apache.camel.processor.Pipeline Pipeline}
056         * will not clone the exchange
057         *
058         * @param processor the processor that will send the exchange
059         * @param exchange  the exchange
060         * @return the current exchange if no copying is required such as for a
061         *         pipeline otherwise a new copy of the exchange is returned.
062         */
063        protected Exchange copyExchangeStrategy(Processor processor, Exchange exchange) {
064            return exchange.copy();
065        }
066    
067        public String toString() {
068            return "TopicLoadBalancer";
069        }
070    }