1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.collections4.functors;
18
19 import java.io.Serializable;
20 import java.util.Collection;
21 import java.util.Objects;
22
23 import org.apache.commons.collections4.Transformer;
24
25 /**
26 * Transformer implementation that chains the specified transformers together.
27 * <p>
28 * The input object is passed to the first transformer. The transformed result
29 * is passed to the second transformer and so on.
30 * </p>
31 *
32 * @since 3.0
33 */
34 public class ChainedTransformer<T> implements Transformer<T, T>, Serializable {
35
36 private static final Transformer[] EMPTY_TRANSFORMER_ARRAY = {};
37
38 /** Serial version UID */
39 private static final long serialVersionUID = 3514945074733160196L;
40
41 /**
42 * Create a new Transformer that calls each transformer in turn, passing the
43 * result into the next transformer. The ordering is that of the iterator()
44 * method on the collection.
45 *
46 * @param <T> the object type
47 * @param transformers a collection of transformers to chain
48 * @return the {@code chained} transformer
49 * @throws NullPointerException if the transformers collection is null
50 * @throws NullPointerException if any transformer in the collection is null
51 */
52 public static <T> Transformer<T, T> chainedTransformer(
53 final Collection<? extends Transformer<? super T, ? extends T>> transformers) {
54 Objects.requireNonNull(transformers, "transformers");
55 if (transformers.isEmpty()) {
56 return NOPTransformer.<T>nopTransformer();
57 }
58 // convert to array like this to guarantee iterator() ordering
59 final Transformer<T, T>[] cmds = transformers.toArray(EMPTY_TRANSFORMER_ARRAY);
60 FunctorUtils.validate(cmds);
61 return new ChainedTransformer<>(false, cmds);
62 }
63
64 /**
65 * Factory method that performs validation and copies the parameter array.
66 *
67 * @param <T> the object type
68 * @param transformers the transformers to chain, copied, no nulls
69 * @return the {@code chained} transformer
70 * @throws NullPointerException if the transformers array is null
71 * @throws NullPointerException if any transformer in the array is null
72 */
73 public static <T> Transformer<T, T> chainedTransformer(final Transformer<? super T, ? extends T>... transformers) {
74 FunctorUtils.validate(transformers);
75 if (transformers.length == 0) {
76 return NOPTransformer.<T>nopTransformer();
77 }
78 return new ChainedTransformer<>(transformers);
79 }
80
81 /** The transformers to call in turn */
82 private final Transformer<? super T, ? extends T>[] iTransformers;
83
84 /**
85 * Hidden constructor for the use by the static factory methods.
86 *
87 * @param clone if {@code true} the input argument will be cloned
88 * @param transformers the transformers to chain, no nulls
89 */
90 private ChainedTransformer(final boolean clone, final Transformer<? super T, ? extends T>[] transformers) {
91 iTransformers = clone ? FunctorUtils.copy(transformers) : transformers;
92 }
93
94 /**
95 * Constructor that performs no validation.
96 * Use {@code chainedTransformer} if you want that.
97 *
98 * @param transformers the transformers to chain, copied, no nulls
99 */
100 public ChainedTransformer(final Transformer<? super T, ? extends T>... transformers) {
101 this(true, transformers);
102 }
103
104 /**
105 * Gets the transformers.
106 *
107 * @return a copy of the transformers
108 * @since 3.1
109 */
110 public Transformer<? super T, ? extends T>[] getTransformers() {
111 return FunctorUtils.<T, T>copy(iTransformers);
112 }
113
114 /**
115 * Transforms the input to result via each decorated transformer
116 *
117 * @param object the input object passed to the first transformer
118 * @return the transformed result
119 */
120 @Override
121 public T transform(T object) {
122 for (final Transformer<? super T, ? extends T> iTransformer : iTransformers) {
123 object = iTransformer.transform(object);
124 }
125 return object;
126 }
127
128 }