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 TypedTupleElementComparator implements StreamComparator<TupleInputStream>, Comparator<Object>
034  {
035  private Class type;
036
037  Comparator comparator = new Comparator<Comparable>()
038  {
039  @Override
040  public int compare( Comparable lhs, Comparable rhs )
041    {
042    if( lhs == null && rhs == null )
043      return 0;
044
045    if( lhs == null )
046      return -1;
047
048    if( rhs == null )
049      return 1;
050
051    return lhs.compareTo( rhs ); // guaranteed to not be null
052    }
053  };
054
055  public TypedTupleElementComparator()
056    {
057    }
058
059  public TypedTupleElementComparator( Class type, Comparator comparator )
060    {
061    this.type = type;
062
063    if( comparator != null )
064      this.comparator = comparator;
065    }
066
067  @Override
068  public int compare( Object lhs, Object rhs )
069    {
070    return comparator.compare( lhs, rhs );
071    }
072
073  @Override
074  public int compare( TupleInputStream lhsStream, TupleInputStream rhsStream )
075    {
076    Object lhs;
077    Object rhs;
078
079    try
080      {
081      lhs = lhsStream.readType( type );
082      rhs = rhsStream.readType( type );
083      }
084    catch( IOException exception )
085      {
086      throw new CascadingException( "unable to read element from underlying stream", exception );
087      }
088
089    try
090      {
091      return comparator.compare( lhs, rhs );
092      }
093    catch( Exception exception )
094      {
095      throw new CascadingException( "unable to compare Tuples, likely a CoGroup is being attempted on fields of " +
096        "different types or custom comparators are incorrectly set on Fields, lhs: '" + lhs + "' rhs: '" + rhs + "'", exception );
097      }
098    }
099  }