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 */
017package org.apache.commons.collections4.functors;
018
019import java.io.Serializable;
020import java.util.Collection;
021
022import org.apache.commons.collections4.Transformer;
023
024/**
025 * Transformer implementation that chains the specified transformers together.
026 * <p>
027 * The input object is passed to the first transformer. The transformed result
028 * is passed to the second transformer and so on.
029 *
030 * @since 3.0
031 * @version $Id: ChainedTransformer.html 972421 2015-11-14 20:00:04Z tn $
032 */
033public class ChainedTransformer<T> implements Transformer<T, T>, Serializable {
034
035    /** Serial version UID */
036    private static final long serialVersionUID = 3514945074733160196L;
037
038    /** The transformers to call in turn */
039    private final Transformer<? super T, ? extends T>[] iTransformers;
040
041    /**
042     * Factory method that performs validation and copies the parameter array.
043     *
044     * @param <T>  the object type
045     * @param transformers  the transformers to chain, copied, no nulls
046     * @return the <code>chained</code> transformer
047     * @throws IllegalArgumentException if the transformers array is null
048     * @throws IllegalArgumentException if any transformer in the array is null
049     */
050    public static <T> Transformer<T, T> chainedTransformer(final Transformer<? super T, ? extends T>... transformers) {
051        FunctorUtils.validate(transformers);
052        if (transformers.length == 0) {
053            return NOPTransformer.<T>nopTransformer();
054        }
055        return new ChainedTransformer<T>(transformers);
056    }
057
058    /**
059     * Create a new Transformer that calls each transformer in turn, passing the
060     * result into the next transformer. The ordering is that of the iterator()
061     * method on the collection.
062     *
063     * @param <T>  the object type
064     * @param transformers  a collection of transformers to chain
065     * @return the <code>chained</code> transformer
066     * @throws IllegalArgumentException if the transformers collection is null
067     * @throws IllegalArgumentException if any transformer in the collection is null
068     */
069    @SuppressWarnings("unchecked")
070    public static <T> Transformer<T, T> chainedTransformer(final Collection<? extends Transformer<T, T>> transformers) {
071        if (transformers == null) {
072            throw new IllegalArgumentException("Transformer collection must not be null");
073        }
074        if (transformers.size() == 0) {
075            return NOPTransformer.<T>nopTransformer();
076        }
077        // convert to array like this to guarantee iterator() ordering
078        final Transformer<T, T>[] cmds = transformers.toArray(new Transformer[transformers.size()]);
079        FunctorUtils.validate(cmds);
080        return new ChainedTransformer<T>(false, cmds);
081    }
082
083    /**
084     * Hidden constructor for the use by the static factory methods.
085     *
086     * @param clone  if {@code true} the input argument will be cloned
087     * @param transformers  the transformers to chain, no nulls
088     */
089    private ChainedTransformer(final boolean clone, final Transformer<? super T, ? extends T>[] transformers) {
090        super();
091        iTransformers = clone ? FunctorUtils.copy(transformers) : transformers;
092    }
093
094    /**
095     * Constructor that performs no validation.
096     * Use <code>chainedTransformer</code> if you want that.
097     *
098     * @param transformers  the transformers to chain, copied, no nulls
099     */
100    public ChainedTransformer(final Transformer<? super T, ? extends T>... transformers) {
101        this(true, transformers);
102    }
103
104    /**
105     * Transforms the input to result via each decorated transformer
106     *
107     * @param object  the input object passed to the first transformer
108     * @return the transformed result
109     */
110    public T transform(T object) {
111        for (final Transformer<? super T, ? extends T> iTransformer : iTransformers) {
112            object = iTransformer.transform(object);
113        }
114        return object;
115    }
116
117    /**
118     * Gets the transformers.
119     *
120     * @return a copy of the transformers
121     * @since 3.1
122     */
123    public Transformer<? super T, ? extends T>[] getTransformers() {
124        return FunctorUtils.<T, T>copy(iTransformers);
125    }
126
127}