001    /*
002     * JBoss, Home of Professional Open Source.
003     * Copyright 2008, Red Hat Middleware LLC, and individual contributors
004     * as indicated by the @author tags. See the copyright.txt file in the
005     * distribution for a full listing of individual contributors. 
006     *
007     * This is free software; you can redistribute it and/or modify it
008     * under the terms of the GNU Lesser General Public License as
009     * published by the Free Software Foundation; either version 2.1 of
010     * the License, or (at your option) any later version.
011     *
012     * This software is distributed in the hope that it will be useful,
013     * but WITHOUT ANY WARRANTY; without even the implied warranty of
014     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
015     * Lesser General Public License for more details.
016     *
017     * You should have received a copy of the GNU Lesser General Public
018     * License along with this software; if not, write to the Free
019     * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
020     * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
021     */
022    package org.jboss.dna.connector.federation.contribution;
023    
024    import net.jcip.annotations.Immutable;
025    import org.jboss.dna.graph.Location;
026    import org.jboss.dna.graph.properties.DateTime;
027    
028    /**
029     * A source contribution that is empty. In other words, the source has no contribution to make.
030     * <p>
031     * Note that this is different than an unknown contribution, which may occur when a source is added to a federated repository
032     * after the contributions have already been determined for nodes. In this case, the new source's contribution for a node is not
033     * known and must be determined.
034     * </p>
035     * 
036     * @author Randall Hauch
037     */
038    @Immutable
039    public class EmptyContribution extends Contribution {
040    
041        /**
042         * This is the first version of this class. See the documentation of MergePlan.serialVersionUID.
043         */
044        private static final long serialVersionUID = 1L;
045    
046        /**
047         * Create a contribution for the source with the supplied name.
048         * 
049         * @param sourceName the name of the source, which may not be null or blank
050         * @param expirationTime the time (in UTC) after which this contribution should be considered expired, or null if there is no
051         *        expiration time
052         */
053        public EmptyContribution( String sourceName,
054                                  DateTime expirationTime ) {
055            super(sourceName, expirationTime);
056            if (ContributionStatistics.RECORD) ContributionStatistics.record(0, 0);
057        }
058    
059        /**
060         * {@inheritDoc}
061         * 
062         * @see org.jboss.dna.connector.federation.contribution.Contribution#getLocationInSource()
063         */
064        @Override
065        public Location getLocationInSource() {
066            return null;
067        }
068    
069        /**
070         * {@inheritDoc}
071         * 
072         * @see org.jboss.dna.connector.federation.contribution.Contribution#isEmpty()
073         */
074        @Override
075        public boolean isEmpty() {
076            return true;
077        }
078    
079        /**
080         * {@inheritDoc}
081         */
082        @Override
083        public boolean equals( Object obj ) {
084            if (obj == this) return true;
085            if (obj instanceof EmptyContribution) {
086                EmptyContribution that = (EmptyContribution)obj;
087                if (!this.getSourceName().equals(that.getSourceName())) return false;
088                return true;
089            }
090            return false;
091        }
092    }