001/*
002 * Licensed to DuraSpace under one or more contributor license agreements.
003 * See the NOTICE file distributed with this work for additional information
004 * regarding copyright ownership.
005 *
006 * DuraSpace licenses this file to you under the Apache License,
007 * Version 2.0 (the "License"); you may not use this file except in
008 * compliance with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.fcrepo.kernel.modeshape.utils;
019
020import java.util.concurrent.atomic.AtomicBoolean;
021
022import org.apache.jena.rdf.listeners.StatementListener;
023import org.apache.jena.rdf.model.Resource;
024import org.apache.jena.rdf.model.Statement;
025
026/**
027 * Listen to Jena statement events to see whether a certain
028 * property was added or removed.
029 *
030 * @author acoburn
031 */
032public class PropertyChangedListener extends StatementListener {
033
034    private final Resource property;
035
036    private final AtomicBoolean changed;
037
038    /**
039     * Create a listener for a particular RDF predicate.
040     *
041     * @param property the predicate for which to watch
042     * @param changed a value to keep track of whether the value changed
043     */
044    public PropertyChangedListener(final Resource property, final AtomicBoolean changed) {
045        this.property = property;
046        this.changed = changed;
047    }
048
049    @Override
050    public void addedStatement(final Statement s) {
051        if (property.equals(s.getPredicate())) {
052            changed.set(true);
053        }
054    }
055
056    @Override
057    public void removedStatement(final Statement s) {
058        if (property.equals(s.getPredicate())) {
059            changed.set(true);
060        }
061    }
062}