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*
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* 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.
*
* @since Commons Collections 3.0
* @version $Revision: 1.5 $ $Date: 2004/01/14 21:43:10 $
*
* @author Stephen Colebourne
*/
public class TransformedMap extends AbstractMapDecorator {
/** 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.
*
* @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 IllegalArgumentException if map is null
*/
public static Map decorate(Map map, Transformer keyTransformer, Transformer valueTransformer) {
return new TransformedMap(map, keyTransformer, valueTransformer);
}
//-----------------------------------------------------------------------
/**
* 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 IllegalArgumentException if map is null
*/
protected TransformedMap(Map map, Transformer keyTransformer, Transformer valueTransformer) {
super(map);
this.keyTransformer = keyTransformer;
this.valueTransformer = valueTransformer;
}
/**
* Transforms a key.
*
* The transformer itself may throw an exception if necessary.
*
* @param object the object to transform
* @throws the transformed object
*/
protected Object transformKey(Object 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
* @throws the transformed object
*/
protected Object transformValue(Object 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
* @throws the transformed object
*/
protected Map transformMap(Map map) {
Map result = new HashMap(map.size());
for (Iterator it = map.entrySet().iterator(); it.hasNext(); ) {
Map.Entry entry = (Map.Entry) it.next();
result.put(transformKey(entry.getKey()), transformValue(entry.getValue()));
}
return result;
}
//-----------------------------------------------------------------------
public Object put(Object key, Object value) {
key = transformKey(key);
value = transformValue(value);
return getMap().put(key, value);
}
public void putAll(Map mapToCopy) {
mapToCopy = transformMap(mapToCopy);
getMap().putAll(mapToCopy);
}
public Set entrySet() {
if (valueTransformer == null) {
return map.entrySet();
}
return new TransformedMapEntrySet(map.entrySet(), valueTransformer);
}
//-----------------------------------------------------------------------
/**
* Implementation of an entry set that uses a transforming map entry.
*/
static class TransformedMapEntrySet extends AbstractCollectionDecorator implements Set {
/** The transformer to use */
private final Transformer valueTransformer;
protected TransformedMapEntrySet(Set set, Transformer valueTransformer) {
super(set);
this.valueTransformer = valueTransformer;
}
public Iterator iterator() {
return new TransformedMapEntrySetIterator(collection.iterator(), valueTransformer);
}
public Object[] toArray() {
Object[] array = collection.toArray();
for (int i = 0; i < array.length; i++) {
array[i] = new TransformedMapEntry((Map.Entry) array[i], valueTransformer);
}
return array;
}
public Object[] toArray(Object array[]) {
Object[] result = array;
if (array.length > 0) {
// we must create a new array to handle multi-threaded situations
// where another thread could access data before we decorate it
result = (Object[]) Array.newInstance(array.getClass().getComponentType(), 0);
}
result = collection.toArray(result);
for (int i = 0; i < result.length; i++) {
result[i] = new TransformedMapEntry((Map.Entry) result[i], valueTransformer);
}
// check to see if result should be returned straight
if (result.length > array.length) {
return result;
}
// copy back into input array to fulfil the method contract
System.arraycopy(result, 0, array, 0, result.length);
if (array.length > result.length) {
array[result.length] = null;
}
return array;
}
}
/**
* Implementation of an entry set iterator.
*/
static class TransformedMapEntrySetIterator extends AbstractIteratorDecorator {
/** The transformer to use */
private final Transformer valueTransformer;
protected TransformedMapEntrySetIterator(Iterator iterator, Transformer valueTransformer) {
super(iterator);
this.valueTransformer = valueTransformer;
}
public Object next() {
Map.Entry entry = (Map.Entry) iterator.next();
return new TransformedMapEntry(entry, valueTransformer);
}
}
/**
* Implementation of a map entry that transforms additions.
*/
static class TransformedMapEntry extends AbstractMapEntryDecorator {
/** The transformer to use */
private final Transformer valueTransformer;
protected TransformedMapEntry(Map.Entry entry, Transformer valueTransformer) {
super(entry);
this.valueTransformer = valueTransformer;
}
public Object setValue(Object object) {
if (valueTransformer != null) {
object = valueTransformer.transform(object);
}
return entry.setValue(object);
}
}
}