    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.map;
    018
    019import java.io.IOException;
    020import java.io.ObjectInputStream;
    021import java.io.ObjectOutputStream;
    022import java.io.Serializable;
    023import java.util.Map;
    024
    025import org.apache.commons.collections4.Transformer;
    026
    027/**
    028 * Decorates another <code>Map</code> to transform objects that are added.
    029 * <p>
    030 * The Map put methods and Map.Entry setValue method are affected by this class.
    031 * Thus objects must be removed or searched for using their transformed form.
    032 * For example, if the transformation converts Strings to Integers, you must
    033 * use the Integer form to remove objects.
    034 * </p>
    035 * <p>
    036 * <strong>Note that TransformedMap is not synchronized and is not thread-safe.</strong>
    037 * If you wish to use this map from multiple threads concurrently, you must use
    038 * appropriate synchronization. The simplest approach is to wrap this map
    039 * using {@link java.util.Collections#synchronizedMap(Map)}. This class may throw
    040 * exceptions when accessed by concurrent threads without synchronization.
    041 * </p>
    042 * <p>
    043 * This class is Serializable from Commons Collections 3.1.
    044 * </p>
    045 *
    046 * @param <K> the type of the keys in this map
    047 * @param <V> the type of the values in this map
    048 *
    049 * @see org.apache.commons.collections4.splitmap.TransformedSplitMap
    050 * @since 3.0
    051 */
    052public class TransformedMap<K, V>
    053        extends AbstractInputCheckedMapDecorator<K, V>
    054        implements Serializable {
    055
    056    /** Serialization version */
    057    private static final long serialVersionUID = 7023152376788900464L;
    058
    059    /** The transformer to use for the key */
    060    protected final Transformer<? super K, ? extends K> keyTransformer;
    061    /** The transformer to use for the value */
    062    protected final Transformer<? super V, ? extends V> valueTransformer;
    063
    064    /**
    065     * Factory method to create a transforming map.
    066     * <p>
    067     * If there are any elements already in the map being decorated, they
    068     * are NOT transformed.
    069     * Contrast this with {@link #transformedMap(Map, Transformer, Transformer)}.
    070     *
    071     * @param <K>  the key type
    072     * @param <V>  the value type
    073     * @param map  the map to decorate, must not be null
    074     * @param keyTransformer  the transformer to use for key conversion, null means no transformation
    075     * @param valueTransformer  the transformer to use for value conversion, null means no transformation
    076     * @return a new transformed map
    077     * @throws NullPointerException if map is null
    078     * @since 4.0
    079     */
    080    public static <K, V> TransformedMap<K, V> transformingMap(final Map<K, V> map,
    081            final Transformer<? super K, ? extends K> keyTransformer,
    082            final Transformer<? super V, ? extends V> valueTransformer) {
    083        return new TransformedMap<>(map, keyTransformer, valueTransformer);
    084    }
    085
    086    /**
    087     * Factory method to create a transforming map that will transform
    088     * existing contents of the specified map.
    089     * <p>
    090     * If there are any elements already in the map being decorated, they
    091     * will be transformed by this method.
    092     * Contrast this with {@link #transformingMap(Map, Transformer, Transformer)}.
    093     *
    094     * @param <K>  the key type
    095     * @param <V>  the value type
    096     * @param map  the map to decorate, must not be null
    097     * @param keyTransformer  the transformer to use for key conversion, null means no transformation
    098     * @param valueTransformer  the transformer to use for value conversion, null means no transformation
    099     * @return a new transformed map
    100     * @throws NullPointerException if map is null
    101     * @since 4.0
    102     */
    103    public static <K, V> TransformedMap<K, V> transformedMap(final Map<K, V> map,
    104            final Transformer<? super K, ? extends K> keyTransformer,
    105            final Transformer<? super V, ? extends V> valueTransformer) {
    106        final TransformedMap<K, V> decorated = new TransformedMap<>(map, keyTransformer, valueTransformer);
    107        if (map.size() > 0) {
    108            final Map<K, V> transformed = decorated.transformMap(map);
    109            decorated.clear();
    110            decorated.decorated().putAll(transformed);  // avoids double transformation
    111        }
    112        return decorated;
    113    }
    114
    115    //-----------------------------------------------------------------------
    116    /**
    117     * Constructor that wraps (not copies).
    118     * <p>
    119     * If there are any elements already in the collection being decorated, they
    120     * are NOT transformed.
    121     *
    122     * @param map  the map to decorate, must not be null
    123     * @param keyTransformer  the transformer to use for key conversion, null means no conversion
    124     * @param valueTransformer  the transformer to use for value conversion, null means no conversion
    125     * @throws NullPointerException if map is null
    126     */
    127    protected TransformedMap(final Map<K, V> map, final Transformer<? super K, ? extends K> keyTransformer,
    128            final Transformer<? super V, ? extends V> valueTransformer) {
    129        super(map);
    130        this.keyTransformer = keyTransformer;
    131        this.valueTransformer = valueTransformer;
    132    }
    133
    134    //-----------------------------------------------------------------------
    135    /**
    136     * Write the map out using a custom routine.
    137     *
    138     * @param out  the output stream
    139     * @throws IOException if an error occurs while writing to the stream
    140     * @since 3.1
    141     */
    142    private void writeObject(final ObjectOutputStream out) throws IOException {
    143        out.defaultWriteObject();
    144        out.writeObject(map);
    145    }
    146
    147    /**
    148     * Read the map in using a custom routine.
    149     *
    150     * @param in  the input stream
    151     * @throws IOException if an error occurs while reading from the stream
    152     * @throws ClassNotFoundException if an object read from the stream can not be loaded
    153     * @since 3.1
    154     */
    155    @SuppressWarnings("unchecked") // (1) should only fail if input stream is incorrect
    156    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
    157        in.defaultReadObject();
    158        map = (Map<K, V>) in.readObject(); // (1)
    159    }
    160
    161    //-----------------------------------------------------------------------
    162    /**
    163     * Transforms a key.
    164     * <p>
    165     * The transformer itself may throw an exception if necessary.
    166     *
    167     * @param object  the object to transform
    168     * @return the transformed object
    169     */
    170    protected K transformKey(final K object) {
    171        if (keyTransformer == null) {
    172            return object;
    173        }
    174        return keyTransformer.transform(object);
    175    }
    176
    177    /**
    178     * Transforms a value.
    179     * <p>
    180     * The transformer itself may throw an exception if necessary.
    181     *
    182     * @param object  the object to transform
    183     * @return the transformed object
    184     */
    185    protected V transformValue(final V object) {
    186        if (valueTransformer == null) {
    187            return object;
    188        }
    189        return valueTransformer.transform(object);
    190    }
    191
    192    /**
    193     * Transforms a map.
    194     * <p>
    195     * The transformer itself may throw an exception if necessary.
    196     *
    197     * @param map  the map to transform
    198     * @return the transformed object
    199     */
    200    @SuppressWarnings("unchecked")
    201    protected Map<K, V> transformMap(final Map<? extends K, ? extends V> map) {
    202        if (map.isEmpty()) {
    203            return (Map<K, V>) map;
    204        }
    205        final Map<K, V> result = new LinkedMap<>(map.size());
    206
    207        for (final Map.Entry<? extends K, ? extends V> entry : map.entrySet()) {
    208            result.put(transformKey(entry.getKey()), transformValue(entry.getValue()));
    209        }
    210        return result;
    211    }
    212
    213    /**
    214     * Override to transform the value when using <code>setValue</code>.
    215     *
    216     * @param value  the value to transform
    217     * @return the transformed value
    218     * @since 3.1
    219     */
    220    @Override
    221    protected V checkSetValue(final V value) {
    222        return valueTransformer.transform(value);
    223    }
    224
    225    /**
    226     * Override to only return true when there is a value transformer.
    227     *
    228     * @return true if a value transformer is in use
    229     * @since 3.1
    230     */
    231    @Override
    232    protected boolean isSetValueChecking() {
    233        return valueTransformer != null;
    234    }
    235
    236    //-----------------------------------------------------------------------
    237    @Override
    238    public V put(K key, V value) {
    239        key = transformKey(key);
    240        value = transformValue(value);
    241        return decorated().put(key, value);
    242    }
    243
    244    @Override
    245    public void putAll(Map<? extends K, ? extends V> mapToCopy) {
    246        mapToCopy = transformMap(mapToCopy);
    247        decorated().putAll(mapToCopy);
    248    }
    249
    250}