    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.splitmap;
    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.Put;
    026import org.apache.commons.collections4.Transformer;
    027import org.apache.commons.collections4.map.LinkedMap;
    028
    029/**
    030 * Decorates another {@link Map} to transform objects that are added.
    031 * <p>
    032 * The Map put methods and Map.Entry setValue method are affected by this class.
    033 * Thus objects must be removed or searched for using their transformed form.
    034 * For example, if the transformation converts Strings to Integers, you must use
    035 * the Integer form to remove objects.
    036 * <p>
    037 * <strong>Note that TransformedMap is not synchronized and is not
    038 * thread-safe.</strong> If you wish to use this map from multiple threads
    039 * concurrently, you must use appropriate synchronization. The simplest approach
    040 * is to wrap this map using {@link java.util.Collections#synchronizedMap(Map)}.
    041 * This class may throw exceptions when accessed by concurrent threads without
    042 * synchronization.
    043 * <p>
    044 * The "put" and "get" type constraints of this class are mutually independent;
    045 * contrast with {@link org.apache.commons.collections4.map.TransformedMap} which,
    046 * by virtue of its implementing {@link Map}&lt;K, V&gt;, must be constructed in such
    047 * a way that its read and write parameters are generalized to a common (super-)type.
    048 * In practice this would often mean <code>&gt;Object, Object&gt;</code>, defeating
    049 * much of the usefulness of having parameterized types.
    050 * <p>
    051 * On the downside, this class is not drop-in compatible with {@link java.util.Map}
    052 * but is intended to be worked with either directly or by {@link Put} and
    053 * {@link org.apache.commons.collections4.Get Get} generalizations.
    054 *
    055 * @param <J> the type of the keys to put in this map
    056 * @param <K> the type of the keys to get in this map
    057 * @param <U> the type of the values to put in this map
    058 * @param <V> the type of the values to get in this map
    059 * @since 4.0
    060 *
    061 * @see org.apache.commons.collections4.SplitMapUtils#readableMap(org.apache.commons.collections4.Get)
    062 * @see org.apache.commons.collections4.SplitMapUtils#writableMap(Put)
    063 */
    064public class TransformedSplitMap<J, K, U, V> extends AbstractIterableGetMapDecorator<K, V>
    065        implements Put<J, U>, Serializable {
    066
    067    /** Serialization version */
    068    private static final long serialVersionUID = 5966875321133456994L;
    069
    070    /** The transformer to use for the key */
    071    private final Transformer<? super J, ? extends K> keyTransformer;
    072    /** The transformer to use for the value */
    073    private final Transformer<? super U, ? extends V> valueTransformer;
    074
    075    /**
    076     * Factory method to create a transforming map.
    077     * <p>
    078     * If there are any elements already in the map being decorated, they are
    079     * NOT transformed.
    080     *
    081     * @param <J>  the input key type
    082     * @param <K>  the output key type
    083     * @param <U>  the input value type
    084     * @param <V>  the output value type
    085     * @param map the map to decorate, must not be null
    086     * @param keyTransformer the transformer to use for key conversion, must not be null
    087     * @param valueTransformer the transformer to use for value conversion, must not be null
    088     * @return a new transformed map
    089     * @throws NullPointerException if map or either of the transformers is null
    090     */
    091    public static <J, K, U, V> TransformedSplitMap<J, K, U, V> transformingMap(final Map<K, V> map,
    092            final Transformer<? super J, ? extends K> keyTransformer,
    093            final Transformer<? super U, ? extends V> valueTransformer) {
    094        return new TransformedSplitMap<>(map, keyTransformer, valueTransformer);
    095    }
    096
    097    //-----------------------------------------------------------------------
    098    /**
    099     * Constructor that wraps (not copies).
    100     * <p>
    101     * If there are any elements already in the collection being decorated, they
    102     * are NOT transformed.
    103     *
    104     * @param map the map to decorate, must not be null
    105     * @param keyTransformer the transformer to use for key conversion, must not be null
    106     * @param valueTransformer the transformer to use for value conversion, must not be null
    107     * @throws NullPointerException if map or either of the transformers is null
    108     */
    109    protected TransformedSplitMap(final Map<K, V> map, final Transformer<? super J, ? extends K> keyTransformer,
    110            final Transformer<? super U, ? extends V> valueTransformer) {
    111        super(map);
    112        if (keyTransformer == null) {
    113            throw new NullPointerException("KeyTransformer must not be null.");
    114        }
    115        this.keyTransformer = keyTransformer;
    116        if (valueTransformer == null) {
    117            throw new NullPointerException("ValueTransformer must not be null.");
    118        }
    119        this.valueTransformer = valueTransformer;
    120    }
    121
    122    //-----------------------------------------------------------------------
    123    /**
    124     * Write the map out using a custom routine.
    125     *
    126     * @param out the output stream
    127     * @throws IOException if an error occurs while writing to the stream
    128     */
    129    private void writeObject(final ObjectOutputStream out) throws IOException {
    130        out.defaultWriteObject();
    131        out.writeObject(decorated());
    132    }
    133
    134    /**
    135     * Read the map in using a custom routine.
    136     *
    137     * @param in the input stream
    138     * @throws IOException if an error occurs while reading from the stream
    139     * @throws ClassNotFoundException if an object read from the stream can not be loaded
    140     * @since 3.1
    141     */
    142    @SuppressWarnings("unchecked") // (1) should only fail if input stream is incorrect
    143    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
    144        in.defaultReadObject();
    145        map = (Map<K, V>) in.readObject(); // (1)
    146    }
    147
    148    //-----------------------------------------------------------------------
    149    /**
    150     * Transforms a key.
    151     * <p>
    152     * The transformer itself may throw an exception if necessary.
    153     *
    154     * @param object the object to transform
    155     * @return the transformed object
    156     */
    157    protected K transformKey(final J object) {
    158        return keyTransformer.transform(object);
    159    }
    160
    161    /**
    162     * Transforms a value.
    163     * <p>
    164     * The transformer itself may throw an exception if necessary.
    165     *
    166     * @param object the object to transform
    167     * @return the transformed object
    168     */
    169    protected V transformValue(final U object) {
    170        return valueTransformer.transform(object);
    171    }
    172
    173    /**
    174     * Transforms a map.
    175     * <p>
    176     * The transformer itself may throw an exception if necessary.
    177     *
    178     * @param map the map to transform
    179     * @return the transformed object
    180     */
    181    @SuppressWarnings("unchecked")
    182    protected Map<K, V> transformMap(final Map<? extends J, ? extends U> map) {
    183        if (map.isEmpty()) {
    184            return (Map<K, V>) map;
    185        }
    186        final Map<K, V> result = new LinkedMap<>(map.size());
    187
    188        for (final Map.Entry<? extends J, ? extends U> entry : map.entrySet()) {
    189            result.put(transformKey(entry.getKey()), transformValue(entry.getValue()));
    190        }
    191        return result;
    192    }
    193
    194    /**
    195     * Override to transform the value when using <code>setValue</code>.
    196     *
    197     * @param value the value to transform
    198     * @return the transformed value
    199     */
    200    protected V checkSetValue(final U value) {
    201        return valueTransformer.transform(value);
    202    }
    203
    204    //-----------------------------------------------------------------------
    205    @Override
    206    public V put(final J key, final U value) {
    207        return decorated().put(transformKey(key), transformValue(value));
    208    }
    209
    210    @Override
    211    public void putAll(final Map<? extends J, ? extends U> mapToCopy) {
    212        decorated().putAll(transformMap(mapToCopy));
    213    }
    214
    215    @Override
    216    public void clear() {
    217        decorated().clear();
    218    }
    219}