Java tutorial
/*************************************************************** * This file is part of the [fleXive](R) project. * * Copyright (c) 1999-2014 * UCS - unique computing solutions gmbh (http://www.ucs.at) * All rights reserved * * The [fleXive](R) project 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. * * The GNU General Public License can be found at * http://www.gnu.org/copyleft/gpl.html. * A copy is found in the textfile GPL.txt and important notices to the * license from the author are found in LICENSE.txt distributed with * these libraries. * * This library 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. * * For further information about UCS - unique computing solutions gmbh, * please see the company website: http://www.ucs.at * * For further information about [fleXive](R), please see the * project website: http://www.flexive.org * * * This copyright notice MUST APPEAR in all copies of the file! ***************************************************************/ package com.flexive.war.beans.admin; import com.flexive.shared.FxSharedUtils; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.w3c.dom.Document; import org.w3c.dom.Node; import org.w3c.dom.NodeList; import org.xml.sax.InputSource; import org.xml.sax.SAXException; import javax.xml.parsers.DocumentBuilder; import javax.xml.parsers.DocumentBuilderFactory; import javax.xml.parsers.ParserConfigurationException; import java.io.IOException; import java.io.InputStream; import java.io.Serializable; import java.net.HttpURLConnection; import java.net.URL; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; import java.util.concurrent.ConcurrentHashMap; /** * Basic RSS provider bean (used on the start page). Feeds are cached in the session. * <p/> * <h3>Usage:</h3> * {@code #{rssProviderBean.feed['http://blog.flexive.org/feed/']}} * * @author Daniel Lichtenberger, UCS * @version $Rev$ * @since 3.0.2 */ public class RssProviderBean implements Serializable { private static final long serialVersionUID = -1235304053736133239L; private static final Log LOG = LogFactory.getLog(RssProviderBean.class); /** * Maximum number of items of a blog feed */ private static final int MAX_ITEMS = 5; public static class RssEntry implements Serializable { private static final long serialVersionUID = 1122438657219678458L; private final String title; private final String link; public RssEntry(String title, String link) { this.title = title; this.link = link; } public String getTitle() { return title; } public String getLink() { return link; } } // cached feeds private final ConcurrentHashMap<String, List<RssEntry>> feeds = new ConcurrentHashMap<String, List<RssEntry>>(); // Map function that returns RssEntries for String URLs private final Map<String, List<RssEntry>> feedMapper = FxSharedUtils .getMappedFunction(new FxSharedUtils.ParameterMapper<String, List<RssEntry>>() { private static final long serialVersionUID = -3824115213705113244L; @Override public List<RssEntry> get(Object key) { if (key == null) { return null; } final String url = key.toString(); List<RssEntry> list = feeds.get(url); if (list == null) { List<RssEntry> cachedList = feeds.putIfAbsent(url, list = fetchFeed(url, MAX_ITEMS)); if (cachedList != null) { list = cachedList; } } return list; } }); private final Map<String, Boolean> feedAvailableMapper = new HashMap<String, Boolean>() { private static final long serialVersionUID = 6292859461365973501L; @SuppressWarnings({ "SuspiciousMethodCalls" }) @Override public Boolean get(Object key) { return feeds.containsKey(key); } }; /** * Return a map that returns the items for a given feed URL, e.g.: * <p> * {@code #{rssProviderBean.feed['http://blog.flexive.org/feed/']}} * </p> * * @return a map that returns the items for a given feed URL. */ public Map<String, List<RssEntry>> getFeed() { return feedMapper; } /** * Return a map that returns a boolean flag if the given feed URL has already been fetched, e.g.:. * <p/> * <p> * {@code #{rssProviderBean.feedAvailable['http://blog.flexive.org/feed']}} * </p> * * @return a map that returns a boolean flag if the given feed URL has already been fetched. */ public Map<String, Boolean> getFeedAvailable() { return feedAvailableMapper; } /** * Fetch and parse a news feed (currently only tested with blog.flexive.org). * * @param url the feed URL * @param maxItems the maximum number of items returned * @return the news items */ private List<RssEntry> fetchFeed(String url, int maxItems) { HttpURLConnection urlConnection = null; InputStream in = null; try { // open url urlConnection = (HttpURLConnection) new URL(url).openConnection(); urlConnection.setConnectTimeout(2000); in = urlConnection.getInputStream(); // parse RSS feed final DocumentBuilder domBuilder = DocumentBuilderFactory.newInstance().newDocumentBuilder(); final Document doc = domBuilder.parse(new InputSource(in)); // iterate over items final NodeList items = doc.getElementsByTagName("item"); final int numItems = Math.min(items.getLength(), maxItems); final List<RssEntry> result = new ArrayList<RssEntry>(numItems); for (int i = 0; i < numItems; i++) { final NodeList childNodes = items.item(i).getChildNodes(); String title = null; String link = null; // find title and link children for (int j = 0; j < childNodes.getLength(); j++) { final Node child = childNodes.item(j); if ("title".equals(child.getNodeName())) { title = child.getTextContent(); if (link != null) { break; } } else if ("link".equals(child.getNodeName())) { link = child.getTextContent(); if (title != null) { break; } } } if (title != null && link != null) { result.add(new RssEntry(title, link)); } } return result; } catch (IOException e) { LOG.error("Failed to fetch stream from " + url + ": " + e.getMessage(), e); return new ArrayList<RssEntry>(0); } catch (SAXException e) { LOG.error("Failed to parse XML stream: " + url + ": " + e.getMessage(), e); return new ArrayList<RssEntry>(0); } catch (ParserConfigurationException e) { LOG.error("Failed to create parser: " + url + ": " + e.getMessage(), e); return new ArrayList<RssEntry>(0); } finally { if (in != null) { try { in.close(); } catch (IOException e) { LOG.warn("Failed to close input stream: " + e.getMessage(), e); } } if (urlConnection != null) { urlConnection.disconnect(); } } } }