    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.tuple.hadoop.util;
    022
    023import java.io.IOException;
    024import java.util.Comparator;
    025
    026import cascading.CascadingException;
    027import cascading.tuple.StreamComparator;
    028import cascading.tuple.io.TupleInputStream;
    029
    030/**
    031 *
    032 */
    033public class TupleElementComparator implements StreamComparator<TupleInputStream>, Comparator<Object>
    034  {
    035  Comparator comparator = new Comparator<Comparable>()
    036  {
    037  @Override
    038  public int compare( Comparable lhs, Comparable rhs )
    039    {
    040    if( lhs == null && rhs == null )
    041      return 0;
    042
    043    if( lhs == null )
    044      return -1;
    045
    046    if( rhs == null )
    047      return 1;
    048
    049    return lhs.compareTo( rhs ); // guaranteed to not be null
    050    }
    051  };
    052
    053  public TupleElementComparator()
    054    {
    055    }
    056
    057  public TupleElementComparator( Comparator comparator )
    058    {
    059    if( comparator != null )
    060      this.comparator = comparator;
    061    }
    062
    063  @Override
    064  public int compare( Object lhs, Object rhs )
    065    {
    066    return comparator.compare( lhs, rhs );
    067    }
    068
    069  @Override
    070  public int compare( TupleInputStream lhsStream, TupleInputStream rhsStream )
    071    {
    072    Object lhs;
    073    Object rhs;
    074
    075    try
    076      {
    077      lhs = lhsStream.getNextElement();
    078      rhs = rhsStream.getNextElement();
    079      }
    080    catch( IOException exception )
    081      {
    082      throw new CascadingException( "unable to read element from underlying stream", exception );
    083      }
    084
    085    try
    086      {
    087      return comparator.compare( lhs, rhs );
    088      }
    089    catch( Exception exception )
    090      {
    091      throw new CascadingException( "unable to compare Tuples, likely a CoGroup is being attempted on fields of " +
    092        "different types or custom comparators are incorrectly set on Fields, lhs: '" + lhs + "' rhs: '" + rhs + "'", exception );
    093      }
    094    }
    095  }