BrowseConsumer.java

/*
 * BrowseConsumer.java
 *
 * Version: $Revision: 3736 $
 *
 * Date: $Date: 2009-04-24 04:16:22 +0000 (Fri, 24 Apr 2009) $
 *
 * Copyright (c) 2002-2009, The DSpace Foundation.  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 DSpace Foundation nor the names of its
 * 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.browse;

import java.util.HashSet;
import java.util.Set;

import org.apache.log4j.Logger;
import org.dspace.content.DSpaceObject;
import org.dspace.content.Item;
import org.dspace.core.Constants;
import org.dspace.core.Context;
import org.dspace.event.Consumer;
import org.dspace.event.Event;

/**
 * Class for updating browse system from content events.
 * Prototype: only Item events recognized.
 *
 * XXX FIXME NOTE:  The Browse Consumer is INCOMPLETE because the
 * deletion of an Item CANNOT be implemented as an event consumer:
 * When an Item is deleted, the browse tables must be updated
 * immediately, within the same transaction, to maintain referential
 * consistency.  It cannot be handled in an Event consumer since by
 * definition that runs after the transaction is committed.
 * Perhaps this can be addressed if the Browse system is replaced.
 *
 * To handle create/modify events:  accumulate Sets of Items to be added
 * and updated out of the event stream.  Process them in endEvents()
 * filter out update requests for Items that were just created.
 *
 * Recommended filter:  Item+Create|Modify|Modify_Metadata:Collection+Add|Remove
 *
 * @version $Revision: 3736 $
 */
public class BrowseConsumer implements Consumer
{
    /** log4j logger */
    private static Logger log = Logger.getLogger(BrowseConsumer.class);

    // items to be updated in browse index
    private Set<Item> toUpdate = null;

    public void initialize()
        throws Exception
    {
       
    }

    public void consume(Context ctx, Event event)
        throws Exception
    {
        if(toUpdate == null)
        {
            toUpdate = new HashSet<Item>();
        }
        
        log.debug("consume() evaluating event: " + event.toString());
        
        
        int st = event.getSubjectType();
        int et = event.getEventType();
        
        switch (st)
        {

        // If an Item is created or its metadata is modified..
        case Constants.ITEM:
            if(et == Event.MODIFY_METADATA || et == Event.CREATE)
            {
                DSpaceObject subj = event.getSubject(ctx);
                if (subj != null)
                {
                    log.debug("consume() adding event to update queue: " + event.toString());
                    toUpdate.add((Item)subj);
                }
            }
            break;
        // track ADD and REMOVE from collections, that changes browse index.
        case Constants.COLLECTION:
            if (event.getObjectType() == Constants.ITEM
                    && (et == Event.ADD || et == Event.REMOVE))
            {
                Item obj = (Item)event.getObject(ctx);
                if (obj != null)
                {
                    log.debug("consume() adding event to update queue: " + event.toString());
                    toUpdate.add(obj);
                }
            }
            break;
        default:
            log.debug("consume() ingnoring event: " + event.toString());
        }
        
    }

    public void end(Context ctx)
        throws Exception
    {
        
        if (toUpdate != null)
        {

            // Update/Add items
            for (Item i : toUpdate)
            {
                // FIXME: there is an exception handling problem here
                try
                {
                    // Update browse indices
                    ctx.turnOffAuthorisationSystem();
                    IndexBrowse ib = new IndexBrowse(ctx);
                    ib.indexItem(i);
                    ctx.restoreAuthSystemState();
                }
                catch (BrowseException e)
                {
                    log.error("caught exception: ", e);
                    //throw new SQLException(e.getMessage());
                }

                if (log.isDebugEnabled())
                    log.debug("Updated browse indices for Item id="
                            + String.valueOf(i.getID()) + ", hdl="
                            + i.getHandle());
            }

            // NOTE: Removed items are necessarily handled inline (ugh).

            // browse updates wrote to the DB, so we have to commit.
            ctx.getDBConnection().commit();

        }
        
        // clean out toUpdate
        toUpdate = null;
    }
    
    public void finish(Context ctx) {
    	
    }
}