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 *      https://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;
024import java.util.Objects;
025
026import org.apache.commons.collections4.Get;
027import org.apache.commons.collections4.Put;
028import org.apache.commons.collections4.Transformer;
029import org.apache.commons.collections4.map.LinkedMap;
030import org.apache.commons.collections4.map.TransformedMap;
031
032/**
033 * Decorates another {@link Map} to transform objects that are added.
034 * <p>
035 * The Map put methods and Map.Entry setValue method are affected by this class.
036 * Thus objects must be removed or searched for using their transformed form.
037 * For example, if the transformation converts Strings to Integers, you must use
038 * the Integer form to remove objects.
039 * </p>
040 * <p>
041 * <strong>Note that TransformedMap is not synchronized and is not
042 * thread-safe.</strong> If you wish to use this map from multiple threads
043 * concurrently, you must use appropriate synchronization. The simplest approach
044 * is to wrap this map using {@link java.util.Collections#synchronizedMap(Map)}.
045 * This class may throw exceptions when accessed by concurrent threads without
046 * synchronization.
047 * </p>
048 * <p>
049 * The "put" and "get" type constraints of this class are mutually independent;
050 * contrast with {@link TransformedMap} which,
051 * by virtue of its implementing {@link Map}&lt;K, V&gt;, must be constructed in such
052 * a way that its read and write parameters are generalized to a common (super-)type.
053 * In practice this would often mean {@code &gt;Object, Object&gt;}, defeating
054 * much of the usefulness of having parameterized types.
055 * </p>
056 * <p>
057 * On the downside, this class is not drop-in compatible with {@link Map}
058 * but is intended to be worked with either directly or by {@link Put} and
059 * {@link Get Get} generalizations.
060 * </p>
061 *
062 * @param <J> The type of the keys to put in this map
063 * @param <K> The type of the keys to get in this map
064 * @param <U> The type of the values to put in this map
065 * @param <V> The type of the values to get in this map
066 * @since 4.0
067 * @see org.apache.commons.collections4.SplitMapUtils#readableMap(org.apache.commons.collections4.Get)
068 * @see org.apache.commons.collections4.SplitMapUtils#writableMap(Put)
069 */
070public class TransformedSplitMap<J, K, U, V> extends AbstractIterableGetMapDecorator<K, V>
071        implements Put<J, U>, Serializable {
072
073    /** Serialization version */
074    private static final long serialVersionUID = 5966875321133456994L;
075
076    /**
077     * Factory method to create a transforming map.
078     * <p>
079     * If there are any elements already in the map being decorated, they are
080     * NOT transformed.
081     *
082     * @param <J>  the input key type
083     * @param <K>  the output key type
084     * @param <U>  the input value type
085     * @param <V>  the output value type
086     * @param map The map to decorate, must not be null
087     * @param keyTransformer The transformer to use for key conversion, must not be null
088     * @param valueTransformer The transformer to use for value conversion, must not be null
089     * @return A new transformed map
090     * @throws NullPointerException if map or either of the transformers is null
091     */
092    public static <J, K, U, V> TransformedSplitMap<J, K, U, V> transformingMap(final Map<K, V> map,
093            final Transformer<? super J, ? extends K> keyTransformer,
094            final Transformer<? super U, ? extends V> valueTransformer) {
095        return new TransformedSplitMap<>(map, keyTransformer, valueTransformer);
096    }
097
098    /** The transformer to use for the key */
099    private final Transformer<? super J, ? extends K> keyTransformer;
100
101    /** The transformer to use for the value */
102    private final Transformer<? super U, ? extends V> valueTransformer;
103
104    /**
105     * Constructor that wraps (not copies).
106     * <p>
107     * If there are any elements already in the collection being decorated, they
108     * are NOT transformed.
109     *
110     * @param map The map to decorate, must not be null
111     * @param keyTransformer The transformer to use for key conversion, must not be null
112     * @param valueTransformer The transformer to use for value conversion, must not be null
113     * @throws NullPointerException if map or either of the transformers is null
114     */
115    protected TransformedSplitMap(final Map<K, V> map, final Transformer<? super J, ? extends K> keyTransformer,
116            final Transformer<? super U, ? extends V> valueTransformer) {
117        super(map);
118        this.keyTransformer = Objects.requireNonNull(keyTransformer, "keyTransformer");
119        this.valueTransformer = Objects.requireNonNull(valueTransformer, "valueTransformer");
120    }
121
122    /**
123     * Override to transform the value when using {@code setValue}.
124     *
125     * @param value The value to transform
126     * @return The transformed value
127     */
128    protected V checkSetValue(final U value) {
129        return valueTransformer.apply(value);
130    }
131
132    @Override
133    public void clear() {
134        decorated().clear();
135    }
136
137    @Override
138    public V put(final J key, final U value) {
139        return decorated().put(transformKey(key), transformValue(value));
140    }
141
142    @Override
143    public void putAll(final Map<? extends J, ? extends U> mapToCopy) {
144        decorated().putAll(transformMap(mapToCopy));
145    }
146
147    /**
148     * Deserializes the map in using a custom routine.
149     *
150     * @param in The input stream
151     * @throws IOException Thrown if an error occurs while reading from the stream
152     * @throws ClassNotFoundException if an object read from the stream cannot 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     * Transforms a key.
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 K transformKey(final J object) {
170        return keyTransformer.apply(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     * Transforms a value.
196     * <p>
197     * The transformer itself may throw an exception if necessary.
198     *
199     * @param object The object to transform
200     * @return The transformed object
201     */
202    protected V transformValue(final U object) {
203        return valueTransformer.apply(object);
204    }
205
206    /**
207     * Serializes this object to an ObjectOutputStream.
208     *
209     * @param out The target ObjectOutputStream.
210     * @throws IOException thrown when an I/O errors occur writing to the target stream.
211     */
212    private void writeObject(final ObjectOutputStream out) throws IOException {
213        out.defaultWriteObject();
214        out.writeObject(decorated());
215    }
216}