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.component.seda.SedaComponent;
025    
026    /**
027     * An implementation of the <a href="http://camel.apache.org/vm.html">VM components</a>
028     * for asynchronous SEDA exchanges on a {@link BlockingQueue} within the classloader tree containing
029     * the camel-core.jar. i.e. to handle communicating across CamelContext instances and possibly across
030     * web application contexts, providing that camel-core.jar is on the system classpath.
031     *
032     * @version 
033     */
034    public class VmComponent extends SedaComponent {
035        protected static final Map<String, QueueReference> QUEUES = new HashMap<String, QueueReference>();
036        private static final AtomicInteger START_COUNTER = new AtomicInteger();
037    
038        @Override
039        public Map<String, QueueReference> getQueues() {
040            return QUEUES;
041        }
042    
043        @Override
044        protected void doStart() throws Exception {
045            super.doStart();
046            START_COUNTER.incrementAndGet();
047        }
048    
049        @Override
050        protected void doStop() throws Exception {
051            if (START_COUNTER.decrementAndGet() <= 0) {
052                // clear queues when no more vm components in use
053                getQueues().clear();
054            }
055        }
056    }