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://camel.apache.org/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: 835186 $
036     */
037    public class VmComponent extends SedaComponent {
038        protected static final Map<String, BlockingQueue<Exchange>> QUEUES = new HashMap<String, BlockingQueue<Exchange>>();
039        private static final AtomicInteger START_COUNTER = new AtomicInteger();
040    
041        @Override
042        protected Endpoint createEndpoint(String uri, String remaining, Map<String, Object> parameters) throws Exception {
043            BlockingQueue<Exchange> blockingQueue = getBlockingQueue(uri, parameters);
044            SedaEndpoint answer = new SedaEndpoint(uri, this, blockingQueue);
045            answer.configureProperties(parameters);
046            return answer;
047        }
048    
049        protected BlockingQueue<Exchange> getBlockingQueue(String uri, Map<String, Object> parameters) {
050            synchronized (QUEUES) {
051                BlockingQueue<Exchange> answer = QUEUES.get(uri);
052                if (answer == null) {
053                    answer = createQueue(uri, parameters);
054                    QUEUES.put(uri, answer);
055                }
056                return answer;
057            }
058        }
059    
060        @Override
061        protected void doStart() throws Exception {
062            super.doStart();
063            START_COUNTER.incrementAndGet();
064        }
065    
066        @Override
067        protected void doStop() throws Exception {
068            super.doStop();
069            if (START_COUNTER.decrementAndGet() == 0) {
070                synchronized (QUEUES) {
071                    for (BlockingQueue<Exchange> q : QUEUES.values()) {
072                        q.clear();
073                    }
074                    QUEUES.clear();
075                }
076            }
077        }
078    }