/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.collections4.splitmap;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.Map;
import org.apache.commons.collections4.Put;
import org.apache.commons.collections4.Transformer;
import org.apache.commons.collections4.map.LinkedMap;
/**
* Decorates another {@link Map} to transform objects that are added.
* <p>
* The Map put methods and Map.Entry setValue method are affected by this class.
* Thus objects must be removed or searched for using their transformed form.
* For example, if the transformation converts Strings to Integers, you must use
* the Integer form to remove objects.
* <p>
* <strong>Note that TransformedMap is not synchronized and is not
* thread-safe.</strong> If you wish to use this map from multiple threads
* concurrently, you must use appropriate synchronization. The simplest approach
* is to wrap this map using {@link java.util.Collections#synchronizedMap(Map)}.
* This class may throw exceptions when accessed by concurrent threads without
* synchronization.
* <p>
* The "put" and "get" type constraints of this class are mutually independent;
* contrast with {@link org.apache.commons.collections4.map.TransformedMap} which,
* by virtue of its implementing {@link Map}<K, V>, must be constructed in such
* a way that its read and write parameters are generalized to a common (super-)type.
* In practice this would often mean <code>>Object, Object></code>, defeating
* much of the usefulness of having parameterized types.
* <p>
* On the downside, this class is not drop-in compatible with {@link java.util.Map}
* but is intended to be worked with either directly or by {@link Put} and
* {@link org.apache.commons.collections4.Get Get} generalizations.
*
* @since 4.0
* @version $Id$
*
* @see org.apache.commons.collections4.SplitMapUtils#readableMap(org.apache.commons.collections4.Get)
* @see org.apache.commons.collections4.SplitMapUtils#writableMap(Put)
*/
public class TransformedSplitMap<J, K, U, V> extends AbstractIterableGetMapDecorator<K, V>
implements Put<J, U>, Serializable {
/** Serialization version */
private static final long serialVersionUID = 5966875321133456994L;
/** The transformer to use for the key */
private final Transformer<? super J, ? extends K> keyTransformer;
/** The transformer to use for the value */
private final Transformer<? super U, ? extends V> valueTransformer;
/**
* Factory method to create a transforming map.
* <p>
* If there are any elements already in the map being decorated, they are
* NOT transformed.
*
* @param <J> the input key type
* @param <K> the output key type
* @param <U> the input value type
* @param <V> the output value type
* @param map the map to decorate, must not be null
* @param keyTransformer the transformer to use for key conversion, must not be null
* @param valueTransformer the transformer to use for value conversion, must not be null
* @return a new transformed map
* @throws NullPointerException if map or either of the transformers is null
*/
public static <J, K, U, V> TransformedSplitMap<J, K, U, V> transformingMap(final Map<K, V> map,
final Transformer<? super J, ? extends K> keyTransformer,
final Transformer<? super U, ? extends V> valueTransformer) {
return new TransformedSplitMap<J, K, U, V>(map, keyTransformer, valueTransformer);
}
//-----------------------------------------------------------------------
/**
* Constructor that wraps (not copies).
* <p>
* If there are any elements already in the collection being decorated, they
* are NOT transformed.
*
* @param map the map to decorate, must not be null
* @param keyTransformer the transformer to use for key conversion, must not be null
* @param valueTransformer the transformer to use for value conversion, must not be null
* @throws NullPointerException if map or either of the transformers is null
*/
protected TransformedSplitMap(final Map<K, V> map, final Transformer<? super J, ? extends K> keyTransformer,
final Transformer<? super U, ? extends V> valueTransformer) {
super(map);
if (keyTransformer == null) {
throw new NullPointerException("KeyTransformer must not be null.");
}
this.keyTransformer = keyTransformer;
if (valueTransformer == null) {
throw new NullPointerException("ValueTransformer must not be null.");
}
this.valueTransformer = valueTransformer;
}
//-----------------------------------------------------------------------
/**
* Write the map out using a custom routine.
*
* @param out the output stream
* @throws IOException
*/
private void writeObject(final ObjectOutputStream out) throws IOException {
out.defaultWriteObject();
out.writeObject(decorated());
}
/**
* Read the map in using a custom routine.
*
* @param in the input stream
* @throws IOException
* @throws ClassNotFoundException
* @since 3.1
*/
@SuppressWarnings("unchecked") // (1) should only fail if input stream is incorrect
private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
in.defaultReadObject();
map = (Map<K, V>) in.readObject(); // (1)
}
//-----------------------------------------------------------------------
/**
* Transforms a key.
* <p>
* The transformer itself may throw an exception if necessary.
*
* @param object the object to transform
* @return the transformed object
*/
protected K transformKey(final J object) {
return keyTransformer.transform(object);
}
/**
* Transforms a value.
* <p>
* The transformer itself may throw an exception if necessary.
*
* @param object the object to transform
* @return the transformed object
*/
protected V transformValue(final U object) {
return valueTransformer.transform(object);
}
/**
* Transforms a map.
* <p>
* The transformer itself may throw an exception if necessary.
*
* @param map the map to transform
* @return the transformed object
*/
@SuppressWarnings("unchecked")
protected Map<K, V> transformMap(final Map<? extends J, ? extends U> map) {
if (map.isEmpty()) {
return (Map<K, V>) map;
}
final Map<K, V> result = new LinkedMap<K, V>(map.size());
for (final Map.Entry<? extends J, ? extends U> entry : map.entrySet()) {
result.put(transformKey(entry.getKey()), transformValue(entry.getValue()));
}
return result;
}
/**
* Override to transform the value when using <code>setValue</code>.
*
* @param value the value to transform
* @return the transformed value
*/
protected V checkSetValue(final U value) {
return valueTransformer.transform(value);
}
//-----------------------------------------------------------------------
@Override
public V put(final J key, final U value) {
return decorated().put(transformKey(key), transformValue(value));
}
@Override
public void putAll(final Map<? extends J, ? extends U> mapToCopy) {
decorated().putAll(transformMap(mapToCopy));
}
@Override
public void clear() {
decorated().clear();
}
}