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}