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: 41580 $
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            if (LOG.isDebugEnabled()) {
062                LOG.debug("Starting to poll: " + this.getEndpoint());
063            }
064            try {
065                poll();
066            } catch (Exception e) {
067                // TODO: We should not swallow this but handle it better. See CAMEL-501
068                LOG.warn("An exception occured while polling: " + this.getEndpoint() + ": " + e.getMessage(), e);
069            }
070        }
071    
072        // Properties
073        // -------------------------------------------------------------------------
074        public long getInitialDelay() {
075            return initialDelay;
076        }
077    
078        public void setInitialDelay(long initialDelay) {
079            this.initialDelay = initialDelay;
080        }
081    
082        public long getDelay() {
083            return delay;
084        }
085    
086        public void setDelay(long delay) {
087            this.delay = delay;
088        }
089    
090        public TimeUnit getTimeUnit() {
091            return timeUnit;
092        }
093    
094        public void setTimeUnit(TimeUnit timeUnit) {
095            this.timeUnit = timeUnit;
096        }
097    
098        public boolean isUseFixedDelay() {
099            return useFixedDelay;
100        }
101    
102        public void setUseFixedDelay(boolean useFixedDelay) {
103            this.useFixedDelay = useFixedDelay;
104        }
105    
106        // Implementation methods
107        // -------------------------------------------------------------------------
108    
109        /**
110         * The polling method which is invoked periodically to poll this consumer
111         * 
112         * @throws Exception can be thrown if an exception occured during polling
113         */
114        protected abstract void poll() throws Exception;
115    
116        @Override
117        protected void doStart() throws Exception {
118            super.doStart();
119            if (isUseFixedDelay()) {
120                future = executor.scheduleWithFixedDelay(this, getInitialDelay(), getDelay(), getTimeUnit());
121            } else {
122                future = executor.scheduleAtFixedRate(this, getInitialDelay(), getDelay(), getTimeUnit());
123            }
124        }
125    
126        @Override
127        protected void doStop() throws Exception {
128            if (future != null) {
129                future.cancel(false);
130            }
131            super.doStop();
132        }
133    }