rssreader.java

OpenCMS内容管理入门指南

/*
 * This library is part of the code for the book: OpenCms for Developers
 *
 * Copyright (c) 2007, 2008 Dan Liliedahl
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
package com.deepthoughts.rss;

import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.util.Iterator;
import java.util.List;

import com.sun.syndication.feed.synd.SyndEntry;
import com.sun.syndication.feed.synd.SyndFeed;
import com.sun.syndication.io.FeedException;
import com.sun.syndication.io.SyndFeedInput;
import com.sun.syndication.io.XmlReader;

/**
 * A simple bean which reads an RSS Feed using ROME.
 */
public class RSSReader {

	/** The URL of the RSS Feed */
	protected String m_strFeed;
	
	/** SyndFeedInput instance */
	protected SyndFeedInput m_input;
	
	/** SyndFeed instance */
	protected SyndFeed m_feed;
	
	/** This contains the list of RSS Items */
	protected List m_lstItems;

	/** This is an iterator for the items */
	protected Iterator m_iItems;

	/** Error message */
	protected String m_strError = "";
	
	/**
	 * Constructor
	 * 
	 * @param Feed the RSS feed to be read
	 */
	public RSSReader(String Feed) {
		m_strFeed = Feed;
		m_input = new SyndFeedInput();
		m_feed = null;
		m_lstItems = null;
		m_iItems = null;
	}

	/**
	 * Reads all items from the given feed.  If an error occurs then nothing will be read but the
	 * error message will be set and may be retrieved using the <code>{@link #getError()}</code> method
	 */
	public boolean readAll() {
		try {
			// Create the URL connection
			URLConnection conn = new URL(m_strFeed).openConnection();
			// some feeds require User-Agent identification
			conn.setRequestProperty("User-Agent", "DeepThoughts RSS Reader");
			// build the feed and read all the entries
			m_feed = m_input.build(new XmlReader(conn));
			m_lstItems = m_feed.getEntries();
			return true;
		} catch (IllegalArgumentException e) {
			m_strError = e.getMessage();
		} catch (MalformedURLException e) {
			m_strError = e.getMessage();
		} catch (FeedException e) {
			m_strError = e.getMessage();
		} catch (IOException e) {
			m_strError = e.getMessage();
		}
		return false;
	}

	/**
	 * Returns the error string.
	 * 
	 * @return String containing any error resulting from attempting to read the feeds
	 */
	public String getError() {
		return m_strError;
	}
	
	/**
	 * Determine if more feed items are in the read feed
	 * 
	 * @return true if more items, else false
	 */
	public boolean hasMore() {
		if (null != m_lstItems) {
			if (null == m_iItems) {
				m_iItems = m_lstItems.iterator();
			}
			return m_iItems.hasNext();
		}
		return false;
	}

	/**
	 * Returns the next feed item.
	 * 
	 * @return SyndEntry for the next feed item
	 */
	public SyndEntry getNext() {
		if (hasMore()) {
			return (SyndEntry) m_iItems.next();
		}
		return null;
	}
}