Java tutorial
/* * SSL-Explorer * * Copyright (C) 2003-2006 3SP LTD. All Rights Reserved * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version 2 of * the License, or (at your option) any later version. * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public * License along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ package com.sslexplorer.rss; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.net.MalformedURLException; import java.net.URL; import java.net.URLConnection; import java.text.DateFormat; import java.util.ArrayList; import java.util.Collection; import java.util.Date; import java.util.HashMap; import java.util.List; import java.util.Map; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import com.sslexplorer.boot.SystemProperties; import com.sslexplorer.boot.Util; import com.sun.syndication.io.SyndFeedInput; /** * Manages RSS feeds used for context sensitive online help. */ public final class FeedManager implements Runnable { /** * Feed connect timeout */ public static final int CONNECT_TIMEOUT = 30000; /** * Feed read timeout */ public static final int READ_TIMEOUT = 30000; private static final Log log = LogFactory.getLog(FeedManager.class); private static final int ONE_DAY_MILLIS = 1000 * 60 * 60 * 24; private static final int FOUR_HOURS_MILLIS = 1000 * 60 * 60 * 4; private static final String HOME_URL = "http://download.3sp.com/"; private static final String FEED_3SP_URL = HOME_URL + "feeds/"; private Map<String, Feed> feeds; private List<String> availableFeeds; private boolean running = false; private Thread thread; private int interval = ONE_DAY_MILLIS; private URL baseLocation; private static FeedManager instance; /** * Default consuctor * * @param baseLocation base feed location */ protected FeedManager(URL baseLocation) { this.baseLocation = baseLocation; feeds = new HashMap<String, Feed>(); availableFeeds = new ArrayList<String>(); } /** * Get an instance of the feed manager * * @return feed manager */ public static FeedManager getInstance() { if (instance == null) { try { URL baseLocation = new URL(SystemProperties.get("sslexplorer.rssFeeds.baseLocation", FEED_3SP_URL)); instance = new FeedManager(baseLocation); } catch (MalformedURLException murle) { try { URL baseLocation = new URL(FEED_3SP_URL); instance = new FeedManager(baseLocation); } catch (MalformedURLException murle2) { // Should not happen throw new Error("Invalid default feed location."); } } } return instance; } /** * Get if the feed manager is currently checking for updates * * @return checking for updates */ public boolean isUpdating() { return running; } /** * Start checking for feed updates * * @throws IllegalStateException if already updating */ public void startUpdating() { if (running) { throw new IllegalStateException("Already updating."); } try { loadAvailable(); } catch (Exception e) { log.error("Failed to get initial feeds. Next update attempt will occur in 4 hours", e); interval = FOUR_HOURS_MILLIS; } thread = new Thread(this, "FeedManager"); thread.setPriority(Thread.MIN_PRIORITY); running = true; if (!isTestMode()) { thread.start(); } } private boolean isTestMode() { return Boolean.valueOf(SystemProperties.get("sslexplorer.testing", "false")); } public void run() { try { while (running) { if (!running) break; if (log.isInfoEnabled()) log.info("Checking for feed updates"); try { retrieveFeeds(); interval = ONE_DAY_MILLIS; } catch (Exception e) { log.error("Failed to check for updated feeds. Will check again in 4 hours"); interval = FOUR_HOURS_MILLIS; } sleep(interval); } } catch (InterruptedException ie) { } finally { running = false; if (log.isInfoEnabled()) { log.info("Stopped checking for RSS updates"); } } } /** * Stop checking for feed updates * * @throws IllegalStateException if not updating */ public void stopUpdating() { if (running) { running = false; synchronized (this) { thread.interrupt(); } } else { if (!isTestMode()) { throw new IllegalStateException("Not updating."); } } } /** * Get a list of available RSS feeds as {@link Feed} objects. * * @param feedName * @return list of feeds */ public Feed getFeed(String feedName) { /** * LDP - If the feed server is down this causes problems with logging into the system * until the server has attempted to obtain all the feeds. If the download server is * causing connection timeouts the server wont be usable for a good while. We should * not care so much about feeds being available so I've removed the synchronization * on the feeds hashtable. */ // synchronized (feeds) { // if (!feeds.containsKey(feedName) && !feedName.equals("${rssFeed}") && // availableFeeds.contains(feedName)) { // try { // Feed feed = new Feed(feedName, new SyndFeedInput(), new URL(baseLocation, feedName + ".xml")); // feeds.put(feedName, feed); // feed.load(); // return feed; // } catch (Exception ex) { // log.error("Failed to load feed.", ex); // } // } return (Feed) feeds.get(feedName); // } } protected Collection<String> getAvailableFeedNames() { return availableFeeds; } private static void sleep(int checkAgainIn) throws InterruptedException { if (log.isInfoEnabled()) log.info("Finished checking for updates / feeds, next check will occur at " + getDateAsString(checkAgainIn)); Thread.sleep(checkAgainIn); } private static String getDateAsString(int checkAgainIn) { return DateFormat.getDateTimeInstance().format(new Date(System.currentTimeMillis() + checkAgainIn)); } protected void retrieveFeeds() throws IOException { if (log.isInfoEnabled()) log.info("Retrieving RSS feeds"); Map<String, Feed> updatedFeeds = new HashMap<String, Feed>(); synchronized (feeds) { for (String feedName : availableFeeds) { try { Feed feed = new Feed(feedName, new SyndFeedInput(), new URL(baseLocation, feedName + ".xml")); updatedFeeds.put(feedName, feed); feed.load(); } catch (Exception ex) { log.error("Failed to load feed.", ex); } } feeds = updatedFeeds; } } protected void loadAvailable() throws IOException { URL location = new URL(baseLocation, "index.txt"); availableFeeds.clear(); URLConnection conx = location.openConnection(); conx.setConnectTimeout(CONNECT_TIMEOUT); conx.setReadTimeout(READ_TIMEOUT); if (log.isInfoEnabled()) { log.info("Retrieving RSS feeds index from " + location); } InputStream inputStream = null; try { inputStream = conx.getInputStream(); BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream)); String line; while ((line = reader.readLine()) != null) { availableFeeds.add(line); } } finally { Util.closeStream(inputStream); } if (log.isInfoEnabled()) log.info("There are " + availableFeeds.size() + " available feeds"); } }