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.processor.resequencer;
018    
019    import java.lang.reflect.InvocationHandler;
020    import java.lang.reflect.Method;
021    import java.lang.reflect.Proxy;
022    import java.util.concurrent.BlockingQueue;
023    
024    import org.apache.camel.Exchange;
025    import org.apache.camel.Processor;
026    import org.apache.commons.logging.Log;
027    import org.apache.commons.logging.LogFactory;
028    
029    /**
030     * A thread that takes re-ordered {@link Exchange}s from a blocking queue and
031     * send them to the linked processor.  
032     * 
033     * @author Martin Krasser
034     * 
035     * @version $Revision
036     */
037    public class SequenceSender extends Thread {
038    
039        private static final Log LOG = LogFactory.getLog(SequenceSender.class);
040        private static final Exchange STOP = createStopSignal();
041        
042        private BlockingQueue<Exchange> queue;
043        private Processor processor;
044        
045        /**
046         * Creates a new {@link SequenceSender} thread.
047         * 
048         * @param processor
049         *            the processor to send re-ordered {@link Exchange}s.
050         */
051        public SequenceSender(Processor processor) {
052            this.processor = processor;
053        }
054        
055        /**
056         * Sets the {@link BlockingQueue} to take messages from.
057         * 
058         * @param queue
059         *            the {@link BlockingQueue} to take messages from.
060         */
061        public void setQueue(BlockingQueue<Exchange> queue) {
062            this.queue = queue;
063        }
064    
065        public void run() {
066            while (true) {
067                try {
068                    Exchange exchange = queue.take();
069                    if (exchange == STOP) {
070                        LOG.info("exit processing loop after cancellation");
071                        return;
072                    }
073                    processor.process(exchange);
074                } catch (InterruptedException e) {
075                    LOG.info("exit processing loop after interrupt");
076                    return;
077                } catch (Exception e) {
078                    LOG.warn("exception during exchange processing");
079                }
080            }
081        }
082        
083        /**
084         * Cancels this thread.
085         */
086        public void cancel() throws InterruptedException {
087            queue.put(STOP);
088        }
089        
090        private static Exchange createStopSignal() {
091            return (Exchange)Proxy.newProxyInstance(SequenceSender.class.getClassLoader(), 
092                    new Class[] {Exchange.class}, createStopHandler());
093        }
094        
095        private static InvocationHandler createStopHandler() {
096            return new InvocationHandler() {
097                public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
098                    throw new RuntimeException("illegal method invocation on stop signal");
099                }
100            };
101        }
102        
103    }