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.pipe.assembly;
023
024import java.beans.ConstructorProperties;
025
026import cascading.operation.Identity;
027import cascading.pipe.Each;
028import cascading.pipe.Pipe;
029import cascading.pipe.SubAssembly;
030import cascading.tuple.Fields;
031
032/**
033 * Class Rename is a {@link SubAssembly} that will rename the fromFields to the names in toFields.
034 * <p>
035 * Note that if any input field names are not given, they will retain their names.
036 */
037public class Rename extends SubAssembly
038  {
039  /**
040   * Rename the fromFields in the current Tuple to the given toFields.
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  }