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: 747062 $
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 callback.done(sync);
064 }
065 }
066 });
067 } else {
068 try {
069 processor.process(exchange);
070 } catch (Exception ex) {
071 exchange.setException(ex);
072 }
073 callback.done(false);
074 }
075 }
076 return sync;
077
078 }
079
080 protected abstract Processor chooseProcessor(List<Processor> processors, Exchange exchange);
081 }