    001    /*
    002     * Copyright (c) 2007-2014 Concurrent, Inc. All Rights Reserved.
    003     *
    004     * Project and contact information: http://www.cascading.org/
    005     *
    006     * This file is part of the Cascading project.
    007     *
    008     * Licensed under the Apache License, Version 2.0 (the "License");
    009     * you may not use this file except in compliance with the License.
    010     * You may obtain a copy of the License at
    011     *
    012     *     http://www.apache.org/licenses/LICENSE-2.0
    013     *
    014     * Unless required by applicable law or agreed to in writing, software
    015     * distributed under the License is distributed on an "AS IS" BASIS,
    016     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    017     * See the License for the specific language governing permissions and
    018     * limitations under the License.
    019     */
    020
    021    package cascading.tap;
    022
    023    import java.io.IOException;
    024
    025    import cascading.flow.FlowProcess;
    026    import cascading.scheme.Scheme;
    027    import cascading.tuple.Fields;
    028    import cascading.tuple.TupleEntryIterator;
    029
    030    /**
    031     * Class SinkTap is an optional base class for sink only Taps.
    032     * <p/>
    033     * Some {@link cascading.tap.Tap} instances may only be sinks (as opposed
    034     * to being a source). These types may subclass SinkTap for convenience or
    035     * set {@link #isSource()} to {@code false} in a custom Tap sub-class.
    036     */
    037    public abstract class SinkTap<Config, Output> extends Tap<Config, Void, Output>
    038      {
    039      protected SinkTap()
    040        {
    041        }
    042
    043      protected SinkTap( Scheme<Config, ?, Output, ?, ?> scheme )
    044        {
    045        super( (Scheme<Config, Void, Output, ?, ?>) scheme );
    046        }
    047
    048      protected SinkTap( Scheme<Config, ?, Output, ?, ?> scheme, SinkMode sinkMode )
    049        {
    050        super( (Scheme<Config, Void, Output, ?, ?>) scheme, sinkMode );
    051        }
    052
    053      @Override
    054      public Fields getSourceFields()
    055        {
    056        throw new UnsupportedOperationException( "unable to source tuple streams via a SinkTap instance" );
    057        }
    058
    059      @Override
    060      public boolean isSource()
    061        {
    062        return false;
    063        }
    064
    065      @Override
    066      public void sourceConfInit( FlowProcess<Config> flowProcess, Config conf )
    067        {
    068        throw new UnsupportedOperationException( "unable to source tuple streams via a SinkTap instance" );
    069        }
    070
    071      @Override
    072      public TupleEntryIterator openForRead( FlowProcess<Config> flowProcess, Void input ) throws IOException
    073        {
    074        throw new UnsupportedOperationException( "unable to open for read via a SinkTap instance" );
    075        }
    076      }