    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 * </p>
    030 *
    031 * @since 3.0
    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 NullPointerException if the transformers array is null
    048     * @throws NullPointerException 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<>(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 NullPointerException if the transformers collection is null
    067     * @throws NullPointerException if any transformer in the collection is null
    068     */
    069    public static <T> Transformer<T, T> chainedTransformer(
    070            final Collection<? extends Transformer<? super T, ? extends T>> transformers) {
    071        if (transformers == null) {
    072            throw new NullPointerException("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<>(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    @Override
    111    public T transform(T object) {
    112        for (final Transformer<? super T, ? extends T> iTransformer : iTransformers) {
    113            object = iTransformer.transform(object);
    114        }
    115        return object;
    116    }
    117
    118    /**
    119     * Gets the transformers.
    120     *
    121     * @return a copy of the transformers
    122     * @since 3.1
    123     */
    124    public Transformer<? super T, ? extends T>[] getTransformers() {
    125        return FunctorUtils.<T, T>copy(iTransformers);
    126    }
    127
    128}