001/*
002 * Copyright (c) 2007-2016 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
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  }