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.impl;
018    
019    import java.util.concurrent.ScheduledExecutorService;
020    import java.util.concurrent.ScheduledFuture;
021    import java.util.concurrent.TimeUnit;
022    
023    import org.apache.camel.Endpoint;
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 useful base class for any consumer which is polling based
031     * 
032     * @version $Revision: 35332 $
033     */
034    public abstract class ScheduledPollConsumer<E extends Exchange> extends DefaultConsumer<E> implements
035        Runnable {
036        private static final transient Log LOG = LogFactory.getLog(ScheduledPollConsumer.class);
037    
038        private final ScheduledExecutorService executor;
039        private long initialDelay = 1000;
040        private long delay = 500;
041        private TimeUnit timeUnit = TimeUnit.MILLISECONDS;
042        private boolean useFixedDelay;
043        private ScheduledFuture<?> future;
044    
045        public ScheduledPollConsumer(DefaultEndpoint<E> endpoint, Processor processor) {
046            this(endpoint, processor, endpoint.getExecutorService());
047        }
048    
049        public ScheduledPollConsumer(Endpoint<E> endpoint, Processor processor, ScheduledExecutorService executor) {
050            super(endpoint, processor);
051            this.executor = executor;
052            if (executor == null) {
053                throw new IllegalArgumentException("A non null ScheduledExecutorService must be provided.");
054            }
055        }
056    
057        /**
058         * Invoked whenever we should be polled
059         */
060        public void run() {
061            LOG.debug("Starting to poll");
062            try {
063                poll();
064            } catch (Exception e) {
065                LOG.warn("Caught: " + e, e);
066            }
067        }
068    
069        // Properties
070        // -------------------------------------------------------------------------
071        public long getInitialDelay() {
072            return initialDelay;
073        }
074    
075        public void setInitialDelay(long initialDelay) {
076            this.initialDelay = initialDelay;
077        }
078    
079        public long getDelay() {
080            return delay;
081        }
082    
083        public void setDelay(long delay) {
084            this.delay = delay;
085        }
086    
087        public TimeUnit getTimeUnit() {
088            return timeUnit;
089        }
090    
091        public void setTimeUnit(TimeUnit timeUnit) {
092            this.timeUnit = timeUnit;
093        }
094    
095        public boolean isUseFixedDelay() {
096            return useFixedDelay;
097        }
098    
099        public void setUseFixedDelay(boolean useFixedDelay) {
100            this.useFixedDelay = useFixedDelay;
101        }
102    
103        // Implementation methods
104        // -------------------------------------------------------------------------
105    
106        /**
107         * The polling method which is invoked periodically to poll this consumer
108         * 
109         * @throws Exception
110         */
111        protected abstract void poll() throws Exception;
112    
113        @Override
114        protected void doStart() throws Exception {
115            super.doStart();
116            if (isUseFixedDelay()) {
117                future = executor.scheduleWithFixedDelay(this, getInitialDelay(), getDelay(), getTimeUnit());
118            } else {
119                future = executor.scheduleAtFixedRate(this, getInitialDelay(), getDelay(), getTimeUnit());
120            }
121        }
122    
123        @Override
124        protected void doStop() throws Exception {
125            if (future != null) {
126                future.cancel(false);
127            }
128            super.doStop();
129        }
130    }