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.Exchange;
022 import org.apache.camel.Processor;
023
024 /**
025 * A base class for {@link LoadBalancer} implementations which choose a single
026 * destination for each exchange (rather like JMS Queues)
027 *
028 * @version $Revision: 770599 $
029 */
030 public abstract class QueueLoadBalancer extends LoadBalancerSupport {
031
032 public void process(Exchange exchange) throws Exception {
033 List<Processor> list = getProcessors();
034 if (list.isEmpty()) {
035 throw new IllegalStateException("No processors available to process " + exchange);
036 }
037 Processor processor = chooseProcessor(list, exchange);
038 if (processor == null) {
039 throw new IllegalStateException("No processors could be chosen to process " + exchange);
040 } else {
041 processor.process(exchange);
042 }
043 }
044
045 protected abstract Processor chooseProcessor(List<Processor> processors, Exchange exchange);
046 }