001 /*
002 * Copyright (c) 2007-2014 Concurrent, 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
021 package cascading.pipe.assembly;
022
023 import java.beans.ConstructorProperties;
024
025 import cascading.operation.Identity;
026 import cascading.pipe.Each;
027 import cascading.pipe.Pipe;
028 import cascading.pipe.SubAssembly;
029 import cascading.tuple.Fields;
030
031 /**
032 * Class Coerce is a {@link SubAssembly} that will coerce all incoming {@link cascading.tuple.Tuple} values to
033 * the given types.
034 * <p/>
035 * If the given type is a primitive ({@code long}), and the tuple value is null, {@code 0} is returned.
036 * If the type is an Object ({@code java.lang.Long}), and the tuple value is {@code null}, {@code null} is returned.
037 * <p/>
038 * Coerce encapsulates the {@link Identity} function.
039 *
040 * @see cascading.pipe.SubAssembly
041 * @see cascading.operation.Identity
042 */
043 public class Coerce extends SubAssembly
044 {
045 /**
046 * Constructor Coerce creates a new Coerce instance that will coerce all input Tuple values.
047 *
048 * @param previous of type Pipe
049 * @param types of type Class...
050 */
051 @ConstructorProperties({"previous", "types"})
052 public Coerce( Pipe previous, Class... types )
053 {
054 super( previous );
055
056 if( types.length > 0 )
057 throw new IllegalArgumentException( "given types array may not be zero length" );
058
059 setTails( new Each( previous, new Identity( types ) ) );
060 }
061
062 /**
063 * Constructor Coerce creates a new Coerce instance that will only coerce the given coerceFields Tuple values.
064 * <p/>
065 * Note the resulting output Tuple will contain all the original incoming Fields.
066 *
067 * @param previous of type Pipe
068 * @param coerceFields of type Fields
069 * @param types of type Class...
070 */
071 @ConstructorProperties({"previous", "coerceFields", "types"})
072 public Coerce( Pipe previous, Fields coerceFields, Class... types )
073 {
074 super( previous );
075
076 if( coerceFields == null )
077 throw new IllegalArgumentException( "coerceFields may not be null" );
078
079 setTails( new Each( previous, coerceFields, new Identity( types ), Fields.REPLACE ) );
080 }
081
082 /**
083 * Constructor Coerce creates a new Coerce instance that will only coerce the given coerceFields Tuple values.
084 * <p/>
085 * The given {@code coerceFields} instance must contain field type information, otherwise an
086 * {@link IllegalArgumentException} will be thrown.
087 * <p/>
088 * Note the resulting output Tuple will contain all the original incoming Fields.
089 *
090 * @param previous of type Pipe
091 * @param coerceFields of type Fields
092 */
093 @ConstructorProperties({"previous", "coerceFields"})
094 public Coerce( Pipe previous, Fields coerceFields )
095 {
096 super( previous );
097
098 if( coerceFields == null )
099 throw new IllegalArgumentException( "coerceFields may not be null" );
100
101 if( !coerceFields.hasTypes() )
102 throw new IllegalArgumentException( "coerceFields must have field types declared" );
103
104 setTails( new Each( previous, coerceFields, new Identity( coerceFields ), Fields.REPLACE ) );
105
106 if( coerceFields.getTypes().length == 0 )
107 throw new IllegalArgumentException( "number of types must not be zero" );
108 }
109 }