feedservlet.java

dspace 用j2ee架构的一个数字图书馆.开源程序

/*
 * FeedServlet.java
 *
 * Version: $Revision: 1.2 $
 *
 * Date: $Date: 2005/11/04 04:43:05 $
 *
 * Copyright (c) 2002-2005, Hewlett-Packard Company and Massachusetts
 * Institute of Technology.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 * - Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 *
 * - Neither the name of the Hewlett-Packard Company nor the name of the
 * Massachusetts Institute of Technology nor the names of their
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
 * TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
 * USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 */

package org.dspace.app.webui.servlet;

import java.io.IOException;
import java.sql.SQLException;
import java.util.Date;
import java.util.Iterator;
import java.util.Map;
import java.util.HashMap;
import java.util.List;
import java.util.ArrayList;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.log4j.Logger;

import com.sun.syndication.feed.rss.Channel;
import com.sun.syndication.feed.rss.Description;
import com.sun.syndication.feed.rss.Image;
import com.sun.syndication.feed.rss.TextInput;
import com.sun.syndication.io.WireFeedOutput;
import com.sun.syndication.io.FeedException;

import org.dspace.app.webui.util.JSPManager;
import org.dspace.authorize.AuthorizeException;
import org.dspace.content.DSpaceObject;
import org.dspace.content.Collection;
import org.dspace.content.Community;
import org.dspace.content.Item;
import org.dspace.content.Bitstream;
import org.dspace.content.DCValue;
import org.dspace.content.DCDate;
import org.dspace.core.LogManager;
import org.dspace.core.ConfigurationManager;
import org.dspace.core.Constants;
import org.dspace.core.Context;
import org.dspace.browse.Browse;
import org.dspace.browse.BrowseScope;
import org.dspace.handle.HandleManager;
import org.dspace.search.Harvest;

/**
 * Servlet for handling requests for a syndication feed. The Handle of the collection
 * or community is extracted from the URL, e.g: <code>/feed/rss_1.0/1234/5678</code>.
 * Currently supports only RSS feed formats.
 * 
 * @author Ben Bosman, Richard Rodgers
 * @version $Revision: 1.2 $
 */
public class FeedServlet extends DSpaceServlet
{
	// one hour in milliseconds
	private static final long HOUR_MSECS = 60 * 60 * 1000;
    /** log4j category */
    private static Logger log = Logger.getLogger(FeedServlet.class);
    
    // are syndication feeds enabled?
    private static boolean enabled = false;
    // number of DSpace items per feed
    private static int itemCount = 0;
    // optional cache of feeds
    private static Map feedCache = null;
    // maximum size of cache - 0 means caching disabled
    private static int cacheSize = 0;
    // how many days to keep a feed in cache before checking currency
    private static int cacheAge = 0;
    // supported syndication formats
    private static List formats = null;
    
    static
    {
    	enabled = ConfigurationManager.getBooleanProperty("webui.feed.enable");
    }
    
    public void init()
    {
    	// read rest of config info if enabled
    	if (enabled)
    	{
    		String fmtsStr = ConfigurationManager.getProperty("webui.feed.formats");
    		if ( fmtsStr != null )
    		{
    			formats = new ArrayList();
    			String[] fmts = fmtsStr.split(",");
    			for (int i = 0; i < fmts.length; i++)
    			{
    				formats.add(fmts[i]);
    			}
    		}
    		itemCount = ConfigurationManager.getIntProperty("webui.feed.items");
    		cacheSize = ConfigurationManager.getIntProperty("webui.feed.cache.size");
    		if (cacheSize > 0)
    		{
    			feedCache = new HashMap();
    	   		cacheAge = ConfigurationManager.getIntProperty("webui.feed.cache.age");
    		}
    	}
    }

    protected void doDSGet(Context context, HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException,
            SQLException, AuthorizeException
	{
        String path = request.getPathInfo();
        String feedType = null;
        String handle = null;

        if (path != null)
        {
            // substring(1) is to remove initial '/'
            path = path.substring(1);
            int split = path.indexOf("/");
            if (split != -1)
            {
            	feedType = path.substring(0,split);
            	handle = path.substring(split+1);
            }
        }

        // Determine if handle is a valid reference
        DSpaceObject dso = HandleManager.resolveToObject(context, handle);
        if (! enabled || dso == null || 
        	(dso.getType() != Constants.COLLECTION && dso.getType() != Constants.COMMUNITY) )
        {
            log.info(LogManager.getHeader(context, "invalid_id", "path=" + path));
            JSPManager.showInvalidIDError(request, response, path, -1);
            return;
        }
        
        // Determine if requested format is supported
        if( feedType == null || ! formats.contains( feedType ) )
        {
            log.info(LogManager.getHeader(context, "invalid_syndformat", "path=" + path));
            JSPManager.showInvalidIDError(request, response, path, -1);
            return;
        }
        
        // Lookup or generate the feed
        Channel channel = null;
        if (feedCache != null)
        {
            // Cache key is handle
        	CacheFeed cFeed = (CacheFeed)feedCache.get(handle);
        	if (cFeed != null)  // cache hit, but...
        	{
        		// Is the feed current?
        		boolean cacheFeedCurrent = false;
        		if (cFeed.timeStamp + (cacheAge * HOUR_MSECS) < System.currentTimeMillis())
        		{
        			cacheFeedCurrent = true;
        		}
        		// Not current, but have any items changed since feed was created/last checked?
        		else if ( ! itemsChanged(context, dso, cFeed.timeStamp))
        		{
        			// no items have changed, re-stamp feed and use it
          			cFeed.timeStamp = System.currentTimeMillis();
          			cacheFeedCurrent = true;
        		}
        		if (cacheFeedCurrent)
        		{
        			channel = cFeed.access();		
        		}
        	}
        }
        
        // either not caching, not found in cache, or feed in cache not current
        if (channel == null)
        {
        	channel = generateFeed(context, dso);
        	if (feedCache != null)
        	{
        		cache(handle, new CacheFeed(channel));
        	}
        }
        
        // set the feed to the requested type & return it
        channel.setFeedType(feedType);
        WireFeedOutput feedWriter = new WireFeedOutput();
        try
        {
        	feedWriter.output(channel, response.getWriter());
        }
        catch( FeedException fex )
        {
        	throw new IOException(fex.getMessage());
        }
    }
       
    private boolean itemsChanged(Context context, DSpaceObject dso, long timeStamp)
            throws SQLException
    {
        // construct start and end dates
        DCDate dcStartDate = new DCDate( new Date(timeStamp) );
        DCDate dcEndDate = new DCDate( new Date(System.currentTimeMillis()) );

        // convert dates to ISO 8601, stripping the time
        String startDate = dcStartDate.toString().substring(0, 10);
        String endDate = dcEndDate.toString().substring(0, 10);
        
        // this invocation should return a non-empty list if even 1 item has changed
        return (Harvest.harvest(context, dso, startDate, endDate,
        		                0, 1, false, false, false).size() > 0);
    }
    
    /**
     * Generate a syndication feed for a collection or community
     * or community
     * 
     * @param context	the DSpace context object
     * 
     * @param dso		DSpace object - collection or community
     * 
     * @return		an object representing the feed
     */
    private Channel generateFeed(Context context, DSpaceObject dso)
    		throws IOException, SQLException
    {
    	// container-level elements
    	String objectUrl = ConfigurationManager.getBooleanProperty("webui.feed.localresolve")
    		? HandleManager.resolveToURL(context, dso.getHandle())
    		: HandleManager.getCanonicalForm(dso.getHandle());   	
    	String dspaceUrl = ConfigurationManager.getProperty("dspace.url");
    	String type = null;
    	String description = null;
    	String title = null;
    	Bitstream logo = null;
    	// browse scope
    	BrowseScope scope = new BrowseScope(context);