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.pipe.assembly;
022
023import java.beans.ConstructorProperties;
024
025import cascading.operation.Identity;
026import cascading.pipe.Each;
027import cascading.pipe.Pipe;
028import cascading.pipe.SubAssembly;
029import cascading.tuple.Fields;
030
031/**
032 * Class Rename is a {@link SubAssembly} that will rename the fromFields to the names in toFields.
033 * <p/>
034 * Note that if any input field names are not given, they will retain their names.
035 */
036public class Rename extends SubAssembly
037  {
038  /**
039   * Rename the fromFields in the current Tuple to the given toFields.
040   * <p/>
041   * <pre>
042   * incoming: {"first", "middle", "last"} -> from:{"middle"} to:{"initial"} -> outgoing:{"first", "last", "initial"}
043   * </pre>
044   *
045   * @param previous   of type Pipe
046   * @param fromFields of type Fields
047   * @param toFields   of type Fields
048   */
049  @ConstructorProperties({"previous", "fromFields", "toFields"})
050  public Rename( Pipe previous, Fields fromFields, Fields toFields )
051    {
052    super( previous );
053
054    if( fromFields == null )
055      throw new IllegalArgumentException( "fromFields may not be null" );
056
057    if( toFields == null )
058      throw new IllegalArgumentException( "toFields may not be null" );
059
060    if( fromFields.isDefined() && fromFields.size() != toFields.size() )
061      throw new IllegalArgumentException( "fields arguments must be same size, from: " + fromFields.printVerbose() + " to: " + toFields.printVerbose() );
062
063    if( !toFields.isDefined() )
064      throw new IllegalArgumentException( "toFields must define field names: " + toFields.printVerbose() );
065
066    setTails( new Each( previous, fromFields, new Identity( toFields ), Fields.SWAP ) );
067    }
068  }