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;
024import java.util.Objects;
025
026import org.apache.commons.collections4.Put;
027import org.apache.commons.collections4.Transformer;
028import org.apache.commons.collections4.map.LinkedMap;
029
030/**
031 * Decorates another {@link Map} to transform objects that are added.
032 * <p>
033 * The Map put methods and Map.Entry setValue method are affected by this class.
034 * Thus objects must be removed or searched for using their transformed form.
035 * For example, if the transformation converts Strings to Integers, you must use
036 * the Integer form to remove objects.
037 * </p>
038 * <p>
039 * <strong>Note that TransformedMap is not synchronized and is not
040 * thread-safe.</strong> If you wish to use this map from multiple threads
041 * concurrently, you must use appropriate synchronization. The simplest approach
042 * is to wrap this map using {@link java.util.Collections#synchronizedMap(Map)}.
043 * This class may throw exceptions when accessed by concurrent threads without
044 * synchronization.
045 * </p>
046 * <p>
047 * The "put" and "get" type constraints of this class are mutually independent;
048 * contrast with {@link org.apache.commons.collections4.map.TransformedMap} which,
049 * by virtue of its implementing {@link Map}&lt;K, V&gt;, must be constructed in such
050 * a way that its read and write parameters are generalized to a common (super-)type.
051 * In practice this would often mean {@code &gt;Object, Object&gt;}, defeating
052 * much of the usefulness of having parameterized types.
053 * </p>
054 * <p>
055 * On the downside, this class is not drop-in compatible with {@link java.util.Map}
056 * but is intended to be worked with either directly or by {@link Put} and
057 * {@link org.apache.commons.collections4.Get Get} generalizations.
058 * </p>
059 *
060 * @param <J> the type of the keys to put in this map
061 * @param <K> the type of the keys to get in this map
062 * @param <U> the type of the values to put in this map
063 * @param <V> the type of the values to get in this map
064 * @since 4.0
065 *
066 * @see org.apache.commons.collections4.SplitMapUtils#readableMap(org.apache.commons.collections4.Get)
067 * @see org.apache.commons.collections4.SplitMapUtils#writableMap(Put)
068 */
069public class TransformedSplitMap<J, K, U, V> extends AbstractIterableGetMapDecorator<K, V>
070        implements Put<J, U>, Serializable {
071
072    /** Serialization version */
073    private static final long serialVersionUID = 5966875321133456994L;
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    /** The transformer to use for the key */
097    private final Transformer<? super J, ? extends K> keyTransformer;
098
099    /** The transformer to use for the value */
100    private final Transformer<? super U, ? extends V> valueTransformer;
101
102    /**
103     * Constructor that wraps (not copies).
104     * <p>
105     * If there are any elements already in the collection being decorated, they
106     * are NOT transformed.
107     *
108     * @param map the map to decorate, must not be null
109     * @param keyTransformer the transformer to use for key conversion, must not be null
110     * @param valueTransformer the transformer to use for value conversion, must not be null
111     * @throws NullPointerException if map or either of the transformers is null
112     */
113    protected TransformedSplitMap(final Map<K, V> map, final Transformer<? super J, ? extends K> keyTransformer,
114            final Transformer<? super U, ? extends V> valueTransformer) {
115        super(map);
116        this.keyTransformer = Objects.requireNonNull(keyTransformer, "keyTransformer");
117        this.valueTransformer = Objects.requireNonNull(valueTransformer, "valueTransformer");
118    }
119
120    /**
121     * Override to transform the value when using {@code setValue}.
122     *
123     * @param value the value to transform
124     * @return the transformed value
125     */
126    protected V checkSetValue(final U value) {
127        return valueTransformer.transform(value);
128    }
129
130    @Override
131    public void clear() {
132        decorated().clear();
133    }
134
135    @Override
136    public V put(final J key, final U value) {
137        return decorated().put(transformKey(key), transformValue(value));
138    }
139
140    @Override
141    public void putAll(final Map<? extends J, ? extends U> mapToCopy) {
142        decorated().putAll(transformMap(mapToCopy));
143    }
144
145    /**
146     * Read the map in using a custom routine.
147     *
148     * @param in the input stream
149     * @throws IOException if an error occurs while reading from the stream
150     * @throws ClassNotFoundException if an object read from the stream can not be loaded
151     * @since 3.1
152     */
153    @SuppressWarnings("unchecked") // (1) should only fail if input stream is incorrect
154    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
155        in.defaultReadObject();
156        map = (Map<K, V>) in.readObject(); // (1)
157    }
158
159    /**
160     * Transforms a key.
161     * <p>
162     * The transformer itself may throw an exception if necessary.
163     *
164     * @param object the object to transform
165     * @return the transformed object
166     */
167    protected K transformKey(final J object) {
168        return keyTransformer.transform(object);
169    }
170
171    /**
172     * Transforms a map.
173     * <p>
174     * The transformer itself may throw an exception if necessary.
175     *
176     * @param map the map to transform
177     * @return the transformed object
178     */
179    @SuppressWarnings("unchecked")
180    protected Map<K, V> transformMap(final Map<? extends J, ? extends U> map) {
181        if (map.isEmpty()) {
182            return (Map<K, V>) map;
183        }
184        final Map<K, V> result = new LinkedMap<>(map.size());
185
186        for (final Map.Entry<? extends J, ? extends U> entry : map.entrySet()) {
187            result.put(transformKey(entry.getKey()), transformValue(entry.getValue()));
188        }
189        return result;
190    }
191
192    /**
193     * Transforms a value.
194     * <p>
195     * The transformer itself may throw an exception if necessary.
196     *
197     * @param object the object to transform
198     * @return the transformed object
199     */
200    protected V transformValue(final U object) {
201        return valueTransformer.transform(object);
202    }
203
204    /**
205     * Write the map out using a custom routine.
206     *
207     * @param out the output stream
208     * @throws IOException if an error occurs while writing to the stream
209     */
210    private void writeObject(final ObjectOutputStream out) throws IOException {
211        out.defaultWriteObject();
212        out.writeObject(decorated());
213    }
214}