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.AsyncProcessor; 023 import org.apache.camel.Exchange; 024 import org.apache.camel.Processor; 025 import org.apache.camel.util.AsyncProcessorConverterHelper; 026 import org.apache.camel.util.AsyncProcessorHelper; 027 028 /** 029 * A base class for {@link LoadBalancer} implementations which choose a single 030 * destination for each exchange (rather like JMS Queues) 031 * 032 * @version 033 */ 034 public abstract class QueueLoadBalancer extends LoadBalancerSupport { 035 036 public boolean process(final Exchange exchange, final AsyncCallback callback) { 037 List<Processor> list = getProcessors(); 038 if (!list.isEmpty()) { 039 Processor processor = chooseProcessor(list, exchange); 040 if (processor == null) { 041 throw new IllegalStateException("No processors could be chosen to process " + exchange); 042 } else { 043 AsyncProcessor albp = AsyncProcessorConverterHelper.convert(processor); 044 boolean sync = AsyncProcessorHelper.process(albp, exchange, new AsyncCallback() { 045 public void done(boolean doneSync) { 046 // only handle the async case 047 if (doneSync) { 048 return; 049 } 050 051 callback.done(false); 052 } 053 }); 054 055 if (!sync) { 056 // will continue routing asynchronously 057 return false; 058 } 059 060 callback.done(true); 061 return true; 062 } 063 } 064 065 // no processors but indicate we are done 066 callback.done(true); 067 return true; 068 } 069 070 public void process(Exchange exchange) throws Exception { 071 AsyncProcessorHelper.process(this, exchange); 072 } 073 074 protected abstract Processor chooseProcessor(List<Processor> processors, Exchange exchange); 075 }