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/*
* 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.map;
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.Transformer;
/**
* Decorates another Map to transform objects that are added.
*
* 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.
*
*
* Note that TransformedMap is not synchronized and is not thread-safe.
* 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.
*
*
* This class is Serializable from Commons Collections 3.1.
*
*
* @param the type of the keys in this map
* @param the type of the values in this map
*
* @see org.apache.commons.collections4.splitmap.TransformedSplitMap
* @since 3.0
*/
public class TransformedMap
extends AbstractInputCheckedMapDecorator
implements Serializable {
/** Serialization version */
private static final long serialVersionUID = 7023152376788900464L;
/** The transformer to use for the key */
protected final Transformer keyTransformer;
/** The transformer to use for the value */
protected final Transformer valueTransformer;
/**
* Factory method to create a transforming map.
*
* If there are any elements already in the map being decorated, they
* are NOT transformed.
* Contrast this with {@link #transformedMap(Map, Transformer, Transformer)}.
*
* @param the key type
* @param the value type
* @param map the map to decorate, must not be null
* @param keyTransformer the transformer to use for key conversion, null means no transformation
* @param valueTransformer the transformer to use for value conversion, null means no transformation
* @return a new transformed map
* @throws NullPointerException if map is null
* @since 4.0
*/
public static TransformedMap transformingMap(final Map map,
final Transformer keyTransformer,
final Transformer valueTransformer) {
return new TransformedMap<>(map, keyTransformer, valueTransformer);
}
/**
* Factory method to create a transforming map that will transform
* existing contents of the specified map.
*
* If there are any elements already in the map being decorated, they
* will be transformed by this method.
* Contrast this with {@link #transformingMap(Map, Transformer, Transformer)}.
*
* @param the key type
* @param the value type
* @param map the map to decorate, must not be null
* @param keyTransformer the transformer to use for key conversion, null means no transformation
* @param valueTransformer the transformer to use for value conversion, null means no transformation
* @return a new transformed map
* @throws NullPointerException if map is null
* @since 4.0
*/
public static TransformedMap transformedMap(final Map map,
final Transformer keyTransformer,
final Transformer valueTransformer) {
final TransformedMap decorated = new TransformedMap<>(map, keyTransformer, valueTransformer);
if (map.size() > 0) {
final Map transformed = decorated.transformMap(map);
decorated.clear();
decorated.decorated().putAll(transformed); // avoids double transformation
}
return decorated;
}
//-----------------------------------------------------------------------
/**
* Constructor that wraps (not copies).
*
* 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, null means no conversion
* @param valueTransformer the transformer to use for value conversion, null means no conversion
* @throws NullPointerException if map is null
*/
protected TransformedMap(final Map map, final Transformer keyTransformer,
final Transformer valueTransformer) {
super(map);
this.keyTransformer = keyTransformer;
this.valueTransformer = valueTransformer;
}
//-----------------------------------------------------------------------
/**
* Write the map out using a custom routine.
*
* @param out the output stream
* @throws IOException if an error occurs while writing to the stream
* @since 3.1
*/
private void writeObject(final ObjectOutputStream out) throws IOException {
out.defaultWriteObject();
out.writeObject(map);
}
/**
* Read the map in using a custom routine.
*
* @param in the input stream
* @throws IOException if an error occurs while reading from the stream
* @throws ClassNotFoundException if an object read from the stream can not be loaded
* @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) in.readObject(); // (1)
}
//-----------------------------------------------------------------------
/**
* Transforms a key.
*
* The transformer itself may throw an exception if necessary.
*
* @param object the object to transform
* @return the transformed object
*/
protected K transformKey(final K object) {
if (keyTransformer == null) {
return object;
}
return keyTransformer.transform(object);
}
/**
* Transforms a value.
*
* The transformer itself may throw an exception if necessary.
*
* @param object the object to transform
* @return the transformed object
*/
protected V transformValue(final V object) {
if (valueTransformer == null) {
return object;
}
return valueTransformer.transform(object);
}
/**
* Transforms a map.
*
* The transformer itself may throw an exception if necessary.
*
* @param map the map to transform
* @return the transformed object
*/
@SuppressWarnings("unchecked")
protected Map transformMap(final Map map) {
if (map.isEmpty()) {
return (Map) map;
}
final Map result = new LinkedMap<>(map.size());
for (final Map.Entry entry : map.entrySet()) {
result.put(transformKey(entry.getKey()), transformValue(entry.getValue()));
}
return result;
}
/**
* Override to transform the value when using setValue.
*
* @param value the value to transform
* @return the transformed value
* @since 3.1
*/
@Override
protected V checkSetValue(final V value) {
return valueTransformer.transform(value);
}
/**
* Override to only return true when there is a value transformer.
*
* @return true if a value transformer is in use
* @since 3.1
*/
@Override
protected boolean isSetValueChecking() {
return valueTransformer != null;
}
//-----------------------------------------------------------------------
@Override
public V put(K key, V value) {
key = transformKey(key);
value = transformValue(value);
return decorated().put(key, value);
}
@Override
public void putAll(Map mapToCopy) {
mapToCopy = transformMap(mapToCopy);
decorated().putAll(mapToCopy);
}
}