001/**
002 * Copyright 2005-2015 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 */
016package org.kuali.rice.krad.devtools.datadictionary;
017
018import org.apache.commons.logging.Log;
019import org.apache.commons.logging.LogFactory;
020
021import java.io.IOException;
022import java.net.URL;
023import java.util.LinkedList;
024import java.util.Map;
025import java.util.concurrent.ConcurrentHashMap;
026import java.util.concurrent.Executors;
027import java.util.concurrent.ScheduledExecutorService;
028import java.util.concurrent.TimeUnit;
029import java.util.zip.CRC32;
030import 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 */
038public 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}