001/* 002 * Copyright (c) 2016-2017 Chris K Wensel <chris@wensel.net>. All Rights Reserved. 003 * Copyright (c) 2007-2017 Xplenty, Inc. All Rights Reserved. 004 * 005 * Project and contact information: http://www.cascading.org/ 006 * 007 * This file is part of the Cascading project. 008 * 009 * Licensed under the Apache License, Version 2.0 (the "License"); 010 * you may not use this file except in compliance with the License. 011 * You may obtain a copy of the License at 012 * 013 * http://www.apache.org/licenses/LICENSE-2.0 014 * 015 * Unless required by applicable law or agreed to in writing, software 016 * distributed under the License is distributed on an "AS IS" BASIS, 017 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 018 * See the License for the specific language governing permissions and 019 * limitations under the License. 020 */ 021 022package cascading.scheme; 023 024import java.io.IOException; 025 026import cascading.flow.FlowProcess; 027import cascading.tap.Tap; 028import cascading.tuple.Fields; 029 030/** 031 * Class NullScheme is a {@link Scheme} that neither reads or writes any values. 032 * <p> 033 * It is typically used as a placeholder where a Scheme instance is needed but generally ignored. 034 */ 035public class NullScheme<Config, Input, Output, SourceContext, SinkContext> extends Scheme<Config, Input, Output, SourceContext, SinkContext> 036 { 037 public NullScheme() 038 { 039 } 040 041 public NullScheme( Fields sourceFields, Fields sinkFields ) 042 { 043 super( sourceFields, sinkFields ); 044 } 045 046 @Override 047 public void sourceConfInit( FlowProcess<? extends Config> flowProcess, Tap<Config, Input, Output> tap, Config conf ) 048 { 049 } 050 051 @Override 052 public void sinkConfInit( FlowProcess<? extends Config> flowProcess, Tap<Config, Input, Output> tap, Config conf ) 053 { 054 } 055 056 @Override 057 public boolean source( FlowProcess<? extends Config> flowProcess, SourceCall<SourceContext, Input> sourceCall ) throws IOException 058 { 059 return false; 060 } 061 062 @Override 063 public void sink( FlowProcess<? extends Config> flowProcess, SinkCall<SinkContext, Output> sinkCall ) throws IOException 064 { 065 066 } 067 068 @Override 069 public String toString() 070 { 071 return getClass().getSimpleName(); 072 } 073 }