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.component.vm;
018    
019    import java.util.HashMap;
020    import java.util.Map;
021    import java.util.concurrent.BlockingQueue;
022    import java.util.concurrent.atomic.AtomicInteger;
023    
024    import org.apache.camel.Endpoint;
025    import org.apache.camel.Exchange;
026    import org.apache.camel.component.seda.SedaComponent;
027    import org.apache.camel.component.seda.SedaEndpoint;
028    
029    /**
030     * An implementation of the <a href="http://activemq.apache.org/camel/vm.html">VM components</a>
031     * for asynchronous SEDA exchanges on a {@link BlockingQueue} within the classloader tree containing
032     * the camel-core.jar. i.e. to handle communicating across CamelContext instances and possibly across
033     * web application contexts, providing that camel-core.jar is on the system classpath.
034     *
035     * @version $Revision: 36321 $
036     */
037    public class VmComponent extends SedaComponent {
038        protected static Map<String, BlockingQueue> queues = new HashMap<String, BlockingQueue>();
039        private static final AtomicInteger START_COUNTER = new AtomicInteger();
040    
041    
042        @Override
043        protected Endpoint createEndpoint(String uri, String remaining, Map parameters) throws Exception {
044            BlockingQueue<Exchange> blockingQueue = getBlockingQueue(uri, parameters);
045            return new SedaEndpoint(uri, this, blockingQueue);
046        }
047    
048        protected BlockingQueue<Exchange> getBlockingQueue(String uri, Map parameters) {
049            synchronized (queues) {
050                BlockingQueue<Exchange> answer = queues.get(uri);
051                if (answer == null) {
052                    answer = createQueue(uri, parameters);
053                    queues.put(uri, answer);
054                }
055                return answer;
056            }
057        }
058    
059        @Override
060        protected void doStart() throws Exception {
061            super.doStart();
062            START_COUNTER.incrementAndGet();
063        }
064    
065        @Override
066        protected void doStop() throws Exception {
067            super.doStop();
068            if (START_COUNTER.decrementAndGet() == 0) {
069                synchronized (queues) {
070                    for (BlockingQueue q : queues.values()) {
071                        q.clear();
072                    }
073                    queues.clear();
074                }
075            }
076        }
077    
078    }