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: 731505 $
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 private Exception firstExceptionThrown;
045
046 public ScheduledPollConsumer(DefaultEndpoint<E> endpoint, Processor processor) {
047 this(endpoint, processor, endpoint.getExecutorService());
048 }
049
050 public ScheduledPollConsumer(Endpoint<E> endpoint, Processor processor, ScheduledExecutorService executor) {
051 super(endpoint, processor);
052 this.executor = executor;
053 if (executor == null) {
054 throw new IllegalArgumentException("A non null ScheduledExecutorService must be provided.");
055 }
056 }
057
058 /**
059 * Invoked whenever we should be polled
060 */
061 public void run() {
062 if (LOG.isTraceEnabled()) {
063 LOG.trace("Starting to poll: " + this.getEndpoint());
064 }
065 try {
066 poll();
067 } catch (Exception e) {
068 LOG.warn("An exception occured while polling: " + this.getEndpoint() + ": " + e.getMessage(), e);
069 if (firstExceptionThrown == null) {
070 firstExceptionThrown = e;
071 }
072 }
073 }
074
075 // Properties
076 // -------------------------------------------------------------------------
077 public long getInitialDelay() {
078 return initialDelay;
079 }
080
081 public void setInitialDelay(long initialDelay) {
082 this.initialDelay = initialDelay;
083 }
084
085 public long getDelay() {
086 return delay;
087 }
088
089 public void setDelay(long delay) {
090 this.delay = delay;
091 }
092
093 public TimeUnit getTimeUnit() {
094 return timeUnit;
095 }
096
097 public void setTimeUnit(TimeUnit timeUnit) {
098 this.timeUnit = timeUnit;
099 }
100
101 public boolean isUseFixedDelay() {
102 return useFixedDelay;
103 }
104
105 public void setUseFixedDelay(boolean useFixedDelay) {
106 this.useFixedDelay = useFixedDelay;
107 }
108
109 // Implementation methods
110 // -------------------------------------------------------------------------
111
112 /**
113 * The polling method which is invoked periodically to poll this consumer
114 *
115 * @throws Exception can be thrown if an exception occurred during polling
116 */
117 protected abstract void poll() throws Exception;
118
119 @Override
120 protected void doStart() throws Exception {
121 firstExceptionThrown = null;
122 super.doStart();
123 if (isUseFixedDelay()) {
124 future = executor.scheduleWithFixedDelay(this, getInitialDelay(), getDelay(), getTimeUnit());
125 } else {
126 future = executor.scheduleAtFixedRate(this, getInitialDelay(), getDelay(), getTimeUnit());
127 }
128 }
129
130 @Override
131 protected void doStop() throws Exception {
132 if (future != null) {
133 future.cancel(false);
134 }
135 super.doStop();
136
137 if (firstExceptionThrown != null) {
138 throw firstExceptionThrown;
139 }
140 }
141 }