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.loadbalancer; 018 019import java.util.List; 020 021import org.apache.camel.AsyncCallback; 022import org.apache.camel.AsyncProcessor; 023import org.apache.camel.Exchange; 024import org.apache.camel.Processor; 025 026/** 027 * A base class for {@link LoadBalancer} implementations which choose a single 028 * destination for each exchange (rather like JMS Queues) 029 * 030 * @version 031 */ 032public abstract class QueueLoadBalancer extends LoadBalancerSupport { 033 034 public boolean process(final Exchange exchange, final AsyncCallback callback) { 035 List<Processor> list = getProcessors(); 036 if (!list.isEmpty()) { 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 if (processor instanceof AsyncProcessor) { 042 AsyncProcessor async = (AsyncProcessor) processor; 043 return async.process(exchange, callback); 044 } else { 045 try { 046 processor.process(exchange); 047 } catch (Exception e) { 048 exchange.setException(e); 049 } 050 callback.done(true); 051 return true; 052 } 053 } 054 } 055 056 // no processors but indicate we are done 057 callback.done(true); 058 return true; 059 } 060 061 protected abstract Processor chooseProcessor(List<Processor> processors, Exchange exchange); 062}