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.component.seda.QueueReference;
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 
036     */
037    public class VmComponent extends SedaComponent {
038        protected static final Map<String, QueueReference> QUEUES = new HashMap<String, QueueReference>();
039        protected static final Map<String, SedaEndpoint> ENDPOINTS = new HashMap<String, SedaEndpoint>();
040        private static final AtomicInteger START_COUNTER = new AtomicInteger();
041    
042        @Override
043        public Map<String, QueueReference> getQueues() {
044            return QUEUES;
045        }
046        
047        @Override
048        public QueueReference getQueueReference(String key) {
049            return QUEUES.get(key);
050        }
051    
052        @Override
053        protected void doStart() throws Exception {
054            super.doStart();
055            START_COUNTER.incrementAndGet();
056        }
057    
058        @Override
059        protected void doStop() throws Exception {
060            if (START_COUNTER.decrementAndGet() <= 0) {
061                // clear queues when no more vm components in use
062                getQueues().clear();
063                // also clear endpoints
064                ENDPOINTS.clear();
065            }
066        }
067    
068        @Override
069        protected Endpoint createEndpoint(String uri, String remaining, Map<String, Object> parameters) throws Exception {
070            if (ENDPOINTS.containsKey(uri)) {
071                return ENDPOINTS.get(uri);
072            }
073    
074            SedaEndpoint answer = (SedaEndpoint) super.createEndpoint(uri, remaining, parameters);
075    
076            ENDPOINTS.put(uri, answer);
077            return answer;
078        }
079    }