/*
* Copyright (c) 2007-2014 Concurrent, Inc. All Rights Reserved.
*
* Project and contact information: http://www.cascading.org/
*
* This file is part of the Cascading project.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package cascading.pipe.assembly;
import java.beans.ConstructorProperties;
import cascading.operation.Identity;
import cascading.pipe.Each;
import cascading.pipe.Pipe;
import cascading.pipe.SubAssembly;
import cascading.tuple.Fields;
/**
* Class Rename is a {@link SubAssembly} that will rename the fromFields to the names in toFields.
* <p/>
* Note that if any input field names are not given, they will retain their names.
*/
public class Rename extends SubAssembly
{
/**
* Rename the fromFields in the current Tuple to the given toFields.
* <p/>
* <pre>
* incoming: {"first", "middle", "last"} -> from:{"middle"} to:{"initial"} -> outgoing:{"first", "last", "initial"}
* </pre>
*
* @param previous of type Pipe
* @param fromFields of type Fields
* @param toFields of type Fields
*/
@ConstructorProperties({"previous", "fromFields", "toFields"})
public Rename( Pipe previous, Fields fromFields, Fields toFields )
{
super( previous );
if( fromFields == null )
throw new IllegalArgumentException( "fromFields may not be null" );
if( toFields == null )
throw new IllegalArgumentException( "toFields may not be null" );
if( fromFields.isDefined() && fromFields.size() != toFields.size() )
throw new IllegalArgumentException( "fields arguments must be same size, from: " + fromFields.printVerbose() + " to: " + toFields.printVerbose() );
if( !toFields.isDefined() )
throw new IllegalArgumentException( "toFields must define field names: " + toFields.printVerbose() );
setTails( new Each( previous, fromFields, new Identity( toFields ), Fields.SWAP ) );
}
}