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.graph.sequencers;
023    
024    import java.io.InputStream;
025    import org.jboss.dna.common.monitor.ProgressMonitor;
026    
027    /**
028     * The interface for a DNA sequencer that processes a property as a stream to extract information from the content and store in
029     * the repository.
030     * <p>
031     * Implementations must provide a no-argument constructor.
032     * </p>
033     * 
034     * @author Randall Hauch
035     */
036    public interface StreamSequencer {
037    
038        /**
039         * Sequence the data found in the supplied stream, placing the output information into the supplied map.
040         * <p>
041         * JBoss DNA's SequencingService determines the sequencers that should be executed by monitoring the changes to one or more
042         * workspaces that it is monitoring. Changes in those workspaces are aggregated and used to determine which sequencers should
043         * be called. If the sequencer implements this interface, then this method is called with the property that is to be sequenced
044         * along with the interface used to register the output. The framework takes care of all the rest.
045         * </p>
046         * <p>
047         * This operation should report progress to the supplied {@link ProgressMonitor}. At the beginning of the operation, call
048         * {@link ProgressMonitor#beginTask(double, org.jboss.dna.common.i18n.I18n, Object...)} with a meaningful message describing
049         * the operation and a total for the amount of work that will be done by this sequencer. Then perform the sequencing work,
050         * periodically reporting work by specifying the {@link ProgressMonitor#worked(double) amount of work} that has was just
051         * completed or by {@link ProgressMonitor#createSubtask(double) creating a subtask} and reporting work against that subtask
052         * monitor.
053         * </p>
054         * <p>
055         * The implementation should also periodically check whether the operation has been
056         * {@link ProgressMonitor#isCancelled() cancelled}. If this method returns true, the implementation should abort all work as
057         * soon as possible and close any resources that were acquired or opened.
058         * </p>
059         * <p>
060         * Finally, the implementation should call {@link ProgressMonitor#done()} when the operation has finished.
061         * </p>
062         * 
063         * @param stream the stream with the data to be sequenced; never <code>null</code>
064         * @param output the output from the sequencing operation; never <code>null</code>
065         * @param context the context for the sequencing operation; never <code>null</code>
066         * @param progressMonitor the progress monitor that should be kept updated with the sequencer's progress and that should be
067         *        frequently consulted as to whether this operation has been {@link ProgressMonitor#isCancelled() cancelled}.
068         */
069        void sequence( InputStream stream,
070                       SequencerOutput output,
071                       SequencerContext context,
072                       ProgressMonitor progressMonitor );
073    }