    001/*
    002 * Copyright (c) 2007-2017 Xplenty, 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
    021package cascading.tap;
    022
    023import java.io.IOException;
    024
    025import cascading.flow.FlowProcess;
    026import cascading.scheme.Scheme;
    027import cascading.tuple.Fields;
    028import 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 */
    037public 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 prepareResourceForRead( Config conf ) throws IOException
    061    {
    062    throw new UnsupportedOperationException( "unable to prepare resource for read via a SinkTap instance" );
    063    }
    064
    065  @Override
    066  public boolean isSource()
    067    {
    068    return false;
    069    }
    070
    071  @Override
    072  public void sourceConfInit( FlowProcess<? extends Config> flowProcess, Config conf )
    073    {
    074    throw new UnsupportedOperationException( "unable to source tuple streams via a SinkTap instance" );
    075    }
    076
    077  @Override
    078  public TupleEntryIterator openForRead( FlowProcess<? extends Config> flowProcess, Void input ) throws IOException
    079    {
    080    throw new UnsupportedOperationException( "unable to open for read via a SinkTap instance" );
    081    }
    082  }