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: 44674 $
036     */
037    public class SequenceSender extends Thread {
038    
039        private static final transient 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 the processor to send re-ordered {@link Exchange}s.
049         */
050        public SequenceSender(Processor processor) {
051            this.processor = processor;
052        }
053        
054        /**
055         * Sets the {@link BlockingQueue} to take messages from.
056         * 
057         * @param queue the {@link BlockingQueue} to take messages from.
058         */
059        public void setQueue(BlockingQueue<Exchange> queue) {
060            this.queue = queue;
061        }
062    
063        public void run() {
064            while (true) {
065                try {
066                    Exchange exchange = queue.take();
067                    if (exchange == STOP) {
068                        LOG.info("Exit processing loop after cancellation");
069                        return;
070                    }
071                    processor.process(exchange);
072                } catch (InterruptedException e) {
073                    LOG.info("Exit processing loop after interrupt");
074                    return;
075                } catch (Exception e) {
076                    LOG.warn("Exception during exchange processing: " + e.getMessage());
077                }
078            }
079        }
080        
081        /**
082         * Cancels this thread.
083         */
084        public void cancel() throws InterruptedException {
085            queue.put(STOP);
086        }
087        
088        private static Exchange createStopSignal() {
089            return (Exchange)Proxy.newProxyInstance(SequenceSender.class.getClassLoader(), 
090                    new Class[] {Exchange.class}, createStopHandler());
091        }
092        
093        private static InvocationHandler createStopHandler() {
094            return new InvocationHandler() {
095                public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
096                    throw new RuntimeException("Illegal method invocation on stop signal");
097                }
098            };
099        }
100        
101    }