001 /**
002 *
003 * Licensed to the Apache Software Foundation (ASF) under one or more
004 * contributor license agreements. See the NOTICE file distributed with
005 * this work for additional information regarding copyright ownership.
006 * The ASF licenses this file to You under the Apache License, Version 2.0
007 * (the "License"); you may not use this file except in compliance with
008 * the License. You may obtain a copy of the License at
009 *
010 * http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018 package org.apache.camel.processor.loadbalancer;
019
020 import org.apache.camel.Exchange;
021 import org.apache.camel.Processor;
022
023 import java.util.List;
024
025 /**
026 * A base class for {@link LoadBalancer} implementations which choose a single destination for each exchange
027 * (rather like JMS Queues)
028 *
029 * @version $Revision: 1.1 $
030 */
031 public abstract class QueueLoadBalancer extends LoadBalancerSupport {
032
033 public void process(Exchange exchange) throws Exception {
034 List<Processor> list = getProcessors();
035 if (list.isEmpty()) {
036 throw new IllegalStateException("No processors available to process " + exchange);
037 }
038 Processor processor = chooseProcessor(list, exchange);
039 if (processor == null) {
040 throw new IllegalStateException("No processors could be chosen to process " + exchange);
041 }
042 else {
043 processor.process(exchange);
044 }
045 }
046
047 protected abstract Processor chooseProcessor(List<Processor> processors, Exchange exchange);
048 }