001 /* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 package org.apache.commons.collections.functors; 018 019 import java.io.Serializable; 020 import java.util.Collection; 021 import java.util.Iterator; 022 023 import org.apache.commons.collections.Transformer; 024 025 /** 026 * Transformer implementation that chains the specified transformers together. 027 * <p> 028 * The input object is passed to the first transformer. The transformed result 029 * is passed to the second transformer and so on. 030 * 031 * @since Commons Collections 3.0 032 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $ 033 * 034 * @author Stephen Colebourne 035 */ 036 public class ChainedTransformer implements Transformer, Serializable { 037 038 /** Serial version UID */ 039 private static final long serialVersionUID = 3514945074733160196L; 040 041 /** The transformers to call in turn */ 042 private final Transformer[] iTransformers; 043 044 /** 045 * Factory method that performs validation and copies the parameter array. 046 * 047 * @param transformers the transformers to chain, copied, no nulls 048 * @return the <code>chained</code> transformer 049 * @throws IllegalArgumentException if the transformers array is null 050 * @throws IllegalArgumentException if any transformer in the array is null 051 */ 052 public static Transformer getInstance(Transformer[] transformers) { 053 FunctorUtils.validate(transformers); 054 if (transformers.length == 0) { 055 return NOPTransformer.INSTANCE; 056 } 057 transformers = FunctorUtils.copy(transformers); 058 return new ChainedTransformer(transformers); 059 } 060 061 /** 062 * Create a new Transformer that calls each transformer in turn, passing the 063 * result into the next transformer. The ordering is that of the iterator() 064 * method on the collection. 065 * 066 * @param transformers a collection of transformers to chain 067 * @return the <code>chained</code> transformer 068 * @throws IllegalArgumentException if the transformers collection is null 069 * @throws IllegalArgumentException if any transformer in the collection is null 070 */ 071 public static Transformer getInstance(Collection transformers) { 072 if (transformers == null) { 073 throw new IllegalArgumentException("Transformer collection must not be null"); 074 } 075 if (transformers.size() == 0) { 076 return NOPTransformer.INSTANCE; 077 } 078 // convert to array like this to guarantee iterator() ordering 079 Transformer[] cmds = new Transformer[transformers.size()]; 080 int i = 0; 081 for (Iterator it = transformers.iterator(); it.hasNext();) { 082 cmds[i++] = (Transformer) it.next(); 083 } 084 FunctorUtils.validate(cmds); 085 return new ChainedTransformer(cmds); 086 } 087 088 /** 089 * Factory method that performs validation. 090 * 091 * @param transformer1 the first transformer, not null 092 * @param transformer2 the second transformer, not null 093 * @return the <code>chained</code> transformer 094 * @throws IllegalArgumentException if either transformer is null 095 */ 096 public static Transformer getInstance(Transformer transformer1, Transformer transformer2) { 097 if (transformer1 == null || transformer2 == null) { 098 throw new IllegalArgumentException("Transformers must not be null"); 099 } 100 Transformer[] transformers = new Transformer[] { transformer1, transformer2 }; 101 return new ChainedTransformer(transformers); 102 } 103 104 /** 105 * Constructor that performs no validation. 106 * Use <code>getInstance</code> if you want that. 107 * 108 * @param transformers the transformers to chain, not copied, no nulls 109 */ 110 public ChainedTransformer(Transformer[] transformers) { 111 super(); 112 iTransformers = transformers; 113 } 114 115 /** 116 * Transforms the input to result via each decorated transformer 117 * 118 * @param object the input object passed to the first transformer 119 * @return the transformed result 120 */ 121 public Object transform(Object object) { 122 for (int i = 0; i < iTransformers.length; i++) { 123 object = iTransformers[i].transform(object); 124 } 125 return object; 126 } 127 128 /** 129 * Gets the transformers, do not modify the array. 130 * @return the transformers 131 * @since Commons Collections 3.1 132 */ 133 public Transformer[] getTransformers() { 134 return iTransformers; 135 } 136 137 }