    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.flow.planner.iso.transformer;
    022
    023import java.util.Set;
    024
    025import cascading.flow.FlowElement;
    026import cascading.flow.planner.graph.ElementGraph;
    027import cascading.flow.planner.graph.ElementGraphs;
    028import cascading.flow.planner.iso.expression.ElementCapture;
    029import cascading.flow.planner.iso.expression.ExpressionGraph;
    030import cascading.flow.planner.iso.finder.Match;
    031
    032/**
    033 * GraphTransformer that uses the supplied factory to generate the replacement FlowElement.
    034 * <p>
    035 * Note: This only works if exactly one FlowElement is being replaced.
    036 */
    037public class ReplaceGraphFactoryBasedTransformer extends MutateGraphTransformer
    038  {
    039  private final String factoryName;
    040
    041  public ReplaceGraphFactoryBasedTransformer( ExpressionGraph filter, String factoryName )
    042    {
    043    super( null, filter );
    044    this.factoryName = factoryName;
    045
    046    if( factoryName == null )
    047      throw new IllegalArgumentException( "factoryName may not be null" );
    048    }
    049
    050  public ReplaceGraphFactoryBasedTransformer( GraphTransformer graphTransformer, ExpressionGraph filter, String factoryName )
    051    {
    052    super( graphTransformer, filter );
    053    this.factoryName = factoryName;
    054
    055    if( factoryName == null )
    056      throw new IllegalArgumentException( "factoryName may not be null" );
    057    }
    058
    059  @Override
    060  protected boolean transformGraphInPlaceUsing( Transformed<ElementGraph> transformed, ElementGraph graph, Match match )
    061    {
    062    ElementFactory elementFactory = transformed.getPlannerContext().getElementFactoryFor( factoryName );
    063
    064    if( elementFactory == null )
    065      return false;
    066
    067    Set<FlowElement> captured = match.getCapturedElements( ElementCapture.Primary );
    068
    069    if( captured.isEmpty() )
    070      return false;
    071    else if( captured.size() != 1 )
    072      throw new IllegalStateException( "expected one, but found multiple flow elements in the match expression: " + captured );
    073
    074    FlowElement replace = captured.iterator().next();
    075    FlowElement replaceWith = elementFactory.create( graph, replace );
    076    ElementGraphs.replaceElementWith( graph, replace, replaceWith );
    077
    078    return true;
    079    }
    080  }