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; 025 026 /** 027 * A base class for {@link LoadBalancer} implementations which choose a single 028 * destination for each exchange (rather like JMS Queues) 029 * 030 * @version $Revision: 64146 $ 031 */ 032 public abstract class QueueLoadBalancer extends LoadBalancerSupport { 033 034 public void process(Exchange exchange) throws Exception { 035 List<Processor> list = getProcessors(); 036 if (list.isEmpty()) { 037 throw new IllegalStateException("No processors available to process " + exchange); 038 } 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 processor.process(exchange); 044 } 045 } 046 047 public boolean process(final Exchange exchange, final AsyncCallback callback) { 048 boolean sync = false; 049 List<Processor> list = getProcessors(); 050 if (list.isEmpty()) { 051 throw new IllegalStateException("No processors available to process " + exchange); 052 } 053 Processor processor = chooseProcessor(list, exchange); 054 if (processor == null) { 055 throw new IllegalStateException("No processors could be chosen to process " + exchange); 056 } else { 057 if (processor instanceof AsyncProcessor) { 058 AsyncProcessor asyncProcessor = (AsyncProcessor)processor; 059 sync = asyncProcessor.process(exchange, new AsyncCallback() { 060 public void done(boolean sync) { 061 // Only handle the async case... 062 if (sync) { 063 return; 064 } else { 065 callback.done(sync); 066 } 067 } 068 }); 069 } else { 070 try { 071 processor.process(exchange); 072 } catch (Exception ex) { 073 exchange.setException(ex); 074 } 075 callback.done(false); 076 } 077 } 078 return sync; 079 080 } 081 082 protected abstract Processor chooseProcessor(List<Processor> processors, Exchange exchange); 083 }