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 Exception e = new IllegalStateException("No processors could be chosen to process " + exchange); 040 exchange.setException(e); 041 } else { 042 if (processor instanceof AsyncProcessor) { 043 AsyncProcessor async = (AsyncProcessor) processor; 044 return async.process(exchange, callback); 045 } else { 046 try { 047 processor.process(exchange); 048 } catch (Exception e) { 049 exchange.setException(e); 050 } 051 callback.done(true); 052 return true; 053 } 054 } 055 } 056 057 // no processors but indicate we are done 058 callback.done(true); 059 return true; 060 } 061 062 protected abstract Processor chooseProcessor(List<Processor> processors, Exchange exchange); 063}