001 /**
002 * Copyright 2005-2013 The Kuali Foundation
003 *
004 * Licensed under the Educational Community License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.opensource.org/licenses/ecl2.php
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016 package org.kuali.rice.krad.devtools.datadictionary;
017
018 import org.apache.commons.logging.Log;
019 import org.apache.commons.logging.LogFactory;
020
021 import java.io.IOException;
022 import java.net.URL;
023 import java.util.LinkedList;
024 import java.util.Map;
025 import java.util.concurrent.ConcurrentHashMap;
026 import java.util.concurrent.Executors;
027 import java.util.concurrent.ScheduledExecutorService;
028 import java.util.concurrent.TimeUnit;
029 import java.util.zip.CRC32;
030 import java.util.zip.CheckedInputStream;
031
032 /**
033 * This is a description of what this class does - gilesp don't forget to fill this in.
034 *
035 * @author Kuali Rice Team (rice.collab@kuali.org)
036 *
037 */
038 public class URLMonitor {
039 private static final Log LOG = LogFactory.getLog(URLMonitor.class);
040
041 private final LinkedList<URLContentChangedListener> listeners = new LinkedList<URLContentChangedListener>();
042 private final Map<URL, Long> resourceMap = new ConcurrentHashMap();
043 private final int reloadIntervalMilliseconds;
044 private final ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
045
046
047 public URLMonitor(int reloadIntervalMilliseconds) {
048 this.reloadIntervalMilliseconds = reloadIntervalMilliseconds;
049 }
050
051 public void shutdownScheduler() {
052 scheduler.shutdown();
053 }
054
055 public synchronized void addListener(URLContentChangedListener listener) {
056
057 listeners.add(listener);
058
059 if (listeners.size() == 1) {
060 scheduler.scheduleAtFixedRate(urlPoller,
061 reloadIntervalMilliseconds, reloadIntervalMilliseconds, TimeUnit.MILLISECONDS);
062 }
063 }
064
065 public void addURI(URL zipUrl) {
066
067 resourceMap.put(zipUrl, getCRC(zipUrl));
068 }
069
070 private Long getCRC(URL zipUrl) {
071 Long result = -1l;
072 try {
073 CRC32 crc = new CRC32();
074 CheckedInputStream cis = new CheckedInputStream(zipUrl.openStream(), crc);
075
076 byte[] buffer = new byte[1024];
077 int length;
078
079 //read the entry from zip file and extract it to disk
080 while( (length = cis.read(buffer)) > 0);
081
082 cis.close();
083
084 result = crc.getValue();
085 } catch (IOException e) {
086 LOG.warn("Unable to calculate CRC, resource doesn't exist?", e);
087 }
088 return result;
089 }
090
091 private final Runnable urlPoller = new Runnable() {
092
093 @Override
094 public void run() {
095 for (Map.Entry<URL, Long> entry : resourceMap.entrySet()) {
096 Long crc = getCRC(entry.getKey());
097
098 if (!entry.getValue().equals(crc)) {
099 entry.setValue(crc);
100 for (URLContentChangedListener listener : listeners) {
101 listener.urlContentChanged(entry.getKey());
102 }
103 }
104 }
105 }
106 };
107
108 public static interface URLContentChangedListener {
109 public void urlContentChanged(URL url);
110 }
111 }