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.Exchange; 022 import org.apache.camel.Processor; 023 024 /** 025 * A base class for {@link LoadBalancer} implementations which choose a single 026 * destination for each exchange (rather like JMS Queues) 027 * 028 * @version $Revision: 35332 $ 029 */ 030 public abstract class QueueLoadBalancer extends LoadBalancerSupport { 031 032 public void process(Exchange exchange) throws Exception { 033 List<Processor> list = getProcessors(); 034 if (list.isEmpty()) { 035 throw new IllegalStateException("No processors available to process " + exchange); 036 } 037 Processor processor = chooseProcessor(list, exchange); 038 if (processor == null) { 039 throw new IllegalStateException("No processors could be chosen to process " + exchange); 040 } else { 041 processor.process(exchange); 042 } 043 } 044 045 protected abstract Processor chooseProcessor(List<Processor> processors, Exchange exchange); 046 }