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 */
017package org.apache.camel.processor.loadbalancer;
018
019import java.util.ArrayList;
020import java.util.List;
021import java.util.concurrent.CopyOnWriteArrayList;
022
023import org.apache.camel.Exchange;
024import org.apache.camel.Navigate;
025import org.apache.camel.Processor;
026import org.apache.camel.support.ServiceSupport;
027import org.apache.camel.util.AsyncProcessorHelper;
028import org.apache.camel.util.ServiceHelper;
029import org.slf4j.Logger;
030import org.slf4j.LoggerFactory;
031
032/**
033 * A default base class for a {@link LoadBalancer} implementation.
034 * <p/>
035 * This implementation is dedicated for asynchronous load balancers.
036 * <p/>
037 * Consider using the {@link SimpleLoadBalancerSupport} if your load balancer does not by nature
038 * support asynchronous routing.
039 *
040 * @version 
041 */
042public abstract class LoadBalancerSupport extends ServiceSupport implements LoadBalancer, Navigate<Processor> {
043
044    protected final Logger log = LoggerFactory.getLogger(getClass());
045    private final List<Processor> processors = new CopyOnWriteArrayList<Processor>();
046
047    public void addProcessor(Processor processor) {
048        processors.add(processor);
049    }
050
051    public void removeProcessor(Processor processor) {
052        processors.remove(processor);
053    }
054
055    public List<Processor> getProcessors() {
056        return processors;
057    }
058
059    public List<Processor> next() {
060        if (!hasNext()) {
061            return null;
062        }
063        return new ArrayList<Processor>(processors);
064    }
065
066    public boolean hasNext() {
067        return processors.size() > 0;
068    }
069
070    protected void doStart() throws Exception {
071        ServiceHelper.startServices(processors);
072    }
073
074    protected void doStop() throws Exception {
075        ServiceHelper.stopServices(processors);
076    }
077
078    @Override
079    protected void doShutdown() throws Exception {
080        ServiceHelper.stopAndShutdownServices(processors);
081        for (Processor processor : processors) {
082            removeProcessor(processor);
083        }
084    }
085
086    public void process(Exchange exchange) throws Exception {
087        AsyncProcessorHelper.process(this, exchange);
088    }
089}