001/**
002 * Copyright 2015 DuraSpace, Inc.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *     http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016package org.fcrepo.camel.processor;
017
018import static java.net.URLEncoder.encode;
019
020import java.io.IOException;
021
022import org.apache.camel.Exchange;
023import org.apache.camel.Message;
024import org.apache.camel.Processor;
025import org.fcrepo.camel.FcrepoHeaders;
026
027/**
028 * Represends a message processor that deletes objects from an
029 * external triplestore.
030 *
031 * @author Aaron Coburn
032 * @since Nov 8, 2014
033 */
034public class SparqlDeleteProcessor implements Processor {
035    /**
036     * Define how the message should be processed.
037     *
038     * @param exchange the current camel message exchange
039     */
040    public void process(final Exchange exchange) throws IOException {
041
042        final Message in = exchange.getIn();
043        final String namedGraph = in.getHeader(FcrepoHeaders.FCREPO_NAMED_GRAPH, String.class);
044        final String subject = ProcessorUtils.getSubjectUri(in);
045
046        /*
047         * N.B. The Sparql update command below deletes all triples with
048         * the defined subject uri (coming from the FCREPO_IDENTIFIER
049         * and FCREPO_BASE_URL headers). It also deletes triples that
050         * have a subject corresponding to that Fcrepo URI plus the
051         * "/fcr:export?format=jcr/xml" string appended to it. This
052         * makes it possible to more completely remove any triples
053         * for a given resource that were added earlier. If fcrepo
054         * ever stops producing triples that are appended with
055         * /fcr:export?format..., then that extra line can be removed.
056         * It would also be possible to recursively delete triples
057         * (by removing any triple whose subject is also an object of
058         * the starting (or context) URI, but that approach tends to delete
059         * too many triples from the triplestore. This command does
060         * not remove blank nodes.
061         */
062        final StringBuilder query = new StringBuilder();
063
064        query.append(ProcessorUtils.deleteWhere(subject, namedGraph));
065        query.append(";\n");
066        query.append(ProcessorUtils.deleteWhere(subject + "/fcr:export?format=jcr/xml", namedGraph));
067
068        in.setBody("update=" + encode(query.toString(), "UTF-8"));
069        in.setHeader(Exchange.HTTP_METHOD, "POST");
070        in.setHeader(Exchange.CONTENT_TYPE, "application/x-www-form-urlencoded");
071   }
072
073}