001 /** 002 * 003 * Licensed to the Apache Software Foundation (ASF) under one or more 004 * contributor license agreements. See the NOTICE file distributed with 005 * this work for additional information regarding copyright ownership. 006 * The ASF licenses this file to You under the Apache License, Version 2.0 007 * (the "License"); you may not use this file except in compliance with 008 * the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, software 013 * distributed under the License is distributed on an "AS IS" BASIS, 014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 015 * See the License for the specific language governing permissions and 016 * limitations under the License. 017 */ 018 package org.apache.camel.processor.loadbalancer; 019 020 import org.apache.camel.Exchange; 021 import org.apache.camel.Processor; 022 023 import java.util.List; 024 025 /** 026 * A base class for {@link LoadBalancer} implementations which choose a single destination for each exchange 027 * (rather like JMS Queues) 028 * 029 * @version $Revision: 1.1 $ 030 */ 031 public abstract class QueueLoadBalancer extends LoadBalancerSupport { 032 033 public void process(Exchange exchange) throws Exception { 034 List<Processor> list = getProcessors(); 035 if (list.isEmpty()) { 036 throw new IllegalStateException("No processors available to process " + exchange); 037 } 038 Processor processor = chooseProcessor(list, exchange); 039 if (processor == null) { 040 throw new IllegalStateException("No processors could be chosen to process " + exchange); 041 } 042 else { 043 processor.process(exchange); 044 } 045 } 046 047 protected abstract Processor chooseProcessor(List<Processor> processors, Exchange exchange); 048 }