org.apache.commons.collections.map.MultiValueMap Maven / Gradle / Ivy
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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.collections.map;
import java.util.AbstractCollection;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import org.apache.commons.collections.Factory;
import org.apache.commons.collections.FunctorException;
import org.apache.commons.collections.MultiMap;
import org.apache.commons.collections.iterators.EmptyIterator;
import org.apache.commons.collections.iterators.IteratorChain;
/**
* A MultiValueMap decorates another map, allowing it to have
* more than one value for a key.
*
* A MultiMap is a Map with slightly different semantics.
* Putting a value into the map will add the value to a Collection at that key.
* Getting a value will return a Collection, holding all the values put to that key.
*
* This implementation is a decorator, allowing any Map implementation
* to be used as the base.
*
* In addition, this implementation allows the type of collection used
* for the values to be controlled. By default, an ArrayList
* is used, however a Class to instantiate may be specified,
* or a factory that returns a Collection instance.
*
* Note that MultiValueMap is not synchronized and is not thread-safe.
* If you wish to use this map from multiple threads concurrently, you must use
* appropriate synchronization. This class may throw exceptions when accessed
* by concurrent threads without synchronization.
*
* @author James Carman
* @author Christopher Berry
* @author James Strachan
* @author Steve Downey
* @author Stephen Colebourne
* @author Julien Buret
* @author Serhiy Yevtushenko
* @version $Revision: 1713175 $ $Date: 2015-11-07 21:47:04 +0100 (Sat, 07 Nov 2015) $
* @since Commons Collections 3.2
*/
public class MultiValueMap extends AbstractMapDecorator implements MultiMap {
/** The factory for creating value collections. */
private final Factory collectionFactory;
/** The cached values. */
private transient Collection values;
/**
* Creates a map which wraps the given map and
* maps keys to ArrayLists.
*
* @param map the map to wrap
*/
public static MultiValueMap decorate(Map map) {
return new MultiValueMap(map, new ReflectionFactory(ArrayList.class));
}
/**
* Creates a map which decorates the given map and
* maps keys to collections of type collectionClass.
*
* @param map the map to wrap
* @param collectionClass the type of the collection class
*/
public static MultiValueMap decorate(Map map, Class collectionClass) {
return new MultiValueMap(map, new ReflectionFactory(collectionClass));
}
/**
* Creates a map which decorates the given map and
* creates the value collections using the supplied collectionFactory.
*
* @param map the map to decorate
* @param collectionFactory the collection factory (must return a Collection object).
*/
public static MultiValueMap decorate(Map map, Factory collectionFactory) {
return new MultiValueMap(map, collectionFactory);
}
//-----------------------------------------------------------------------
/**
* Creates a MultiValueMap based on a HashMap and
* storing the multiple values in an ArrayList.
*/
public MultiValueMap() {
this(new HashMap(), new ReflectionFactory(ArrayList.class));
}
/**
* Creates a MultiValueMap which decorates the given map and
* creates the value collections using the supplied collectionFactory.
*
* @param map the map to decorate
* @param collectionFactory the collection factory which must return a Collection instance
*/
protected MultiValueMap(Map map, Factory collectionFactory) {
super(map);
if (collectionFactory == null) {
throw new IllegalArgumentException("The factory must not be null");
}
this.collectionFactory = collectionFactory;
}
//-----------------------------------------------------------------------
/**
* Clear the map.
*/
public void clear() {
// If you believe that you have GC issues here, try uncommenting this code
// Set pairs = getMap().entrySet();
// Iterator pairsIterator = pairs.iterator();
// while (pairsIterator.hasNext()) {
// Map.Entry keyValuePair = (Map.Entry) pairsIterator.next();
// Collection coll = (Collection) keyValuePair.getValue();
// coll.clear();
// }
getMap().clear();
}
/**
* Removes a specific value from map.
*
* The item is removed from the collection mapped to the specified key.
* Other values attached to that key are unaffected.
*
* If the last value for a key is removed, null will be returned
* from a subsequant get(key).
*
* @param key the key to remove from
* @param value the value to remove
* @return the value removed (which was passed in), null if nothing removed
*/
public Object remove(Object key, Object value) {
Collection valuesForKey = getCollection(key);
if (valuesForKey == null) {
return null;
}
boolean removed = valuesForKey.remove(value);
if (removed == false) {
return null;
}
if (valuesForKey.isEmpty()) {
remove(key);
}
return value;
}
/**
* Checks whether the map contains the value specified.
*
* This checks all collections against all keys for the value, and thus could be slow.
*
* @param value the value to search for
* @return true if the map contains the value
*/
public boolean containsValue(Object value) {
Set pairs = getMap().entrySet();
if (pairs == null) {
return false;
}
Iterator pairsIterator = pairs.iterator();
while (pairsIterator.hasNext()) {
Map.Entry keyValuePair = (Map.Entry) pairsIterator.next();
Collection coll = (Collection) keyValuePair.getValue();
if (coll.contains(value)) {
return true;
}
}
return false;
}
/**
* Adds the value to the collection associated with the specified key.
*
* Unlike a normal Map the previous value is not replaced.
* Instead the new value is added to the collection stored against the key.
*
* @param key the key to store against
* @param value the value to add to the collection at the key
* @return the value added if the map changed and null if the map did not change
*/
public Object put(Object key, Object value) {
boolean result = false;
Collection coll = getCollection(key);
if (coll == null) {
coll = createCollection(1);
result = coll.add(value);
if (coll.size() > 0) {
// only add if non-zero size to maintain class state
getMap().put(key, coll);
result = true; // map definitely changed
}
} else {
result = coll.add(value);
}
return (result ? value : null);
}
/**
* Override superclass to ensure that MultiMap instances are
* correctly handled.
*
* If you call this method with a normal map, each entry is
* added using put(Object,Object).
* If you call this method with a multi map, each entry is
* added using putAll(Object,Collection).
*
* @param map the map to copy (either a normal or multi map)
*/
public void putAll(Map map) {
if (map instanceof MultiMap) {
for (Iterator it = map.entrySet().iterator(); it.hasNext();) {
Map.Entry entry = (Map.Entry) it.next();
Collection coll = (Collection) entry.getValue();
putAll(entry.getKey(), coll);
}
} else {
for (Iterator it = map.entrySet().iterator(); it.hasNext();) {
Map.Entry entry = (Map.Entry) it.next();
put(entry.getKey(), entry.getValue());
}
}
}
/**
* Gets a collection containing all the values in the map.
*
* This returns a collection containing the combination of values from all keys.
*
* @return a collection view of the values contained in this map
*/
public Collection values() {
Collection vs = values;
return (vs != null ? vs : (values = new Values()));
}
/**
* Checks whether the collection at the specified key contains the value.
*
* @param value the value to search for
* @return true if the map contains the value
*/
public boolean containsValue(Object key, Object value) {
Collection coll = getCollection(key);
if (coll == null) {
return false;
}
return coll.contains(value);
}
/**
* Gets the collection mapped to the specified key.
* This method is a convenience method to typecast the result of get(key).
*
* @param key the key to retrieve
* @return the collection mapped to the key, null if no mapping
*/
public Collection getCollection(Object key) {
return (Collection) getMap().get(key);
}
/**
* Gets the size of the collection mapped to the specified key.
*
* @param key the key to get size for
* @return the size of the collection at the key, zero if key not in map
*/
public int size(Object key) {
Collection coll = getCollection(key);
if (coll == null) {
return 0;
}
return coll.size();
}
/**
* Adds a collection of values to the collection associated with
* the specified key.
*
* @param key the key to store against
* @param values the values to add to the collection at the key, null ignored
* @return true if this map changed
*/
public boolean putAll(Object key, Collection values) {
if (values == null || values.size() == 0) {
return false;
}
boolean result = false;
Collection coll = getCollection(key);
if (coll == null) {
coll = createCollection(values.size());
coll.addAll(values);
if (coll.size() > 0) {
// only add if non-zero size to maintain class state
getMap().put(key, coll);
result = true; // map definitely changed
}
} else {
result = coll.addAll(values);
}
return result;
}
/**
* Gets an iterator for the collection mapped to the specified key.
*
* @param key the key to get an iterator for
* @return the iterator of the collection at the key, empty iterator if key not in map
*/
public Iterator iterator(Object key) {
if (!containsKey(key)) {
return EmptyIterator.INSTANCE;
} else {
return new ValuesIterator(key);
}
}
/**
* Gets the total size of the map by counting all the values.
*
* @return the total size of the map counting all values
*/
public int totalSize() {
int total = 0;
Collection values = getMap().values();
for (Iterator it = values.iterator(); it.hasNext();) {
Collection coll = (Collection) it.next();
total += coll.size();
}
return total;
}
/**
* Creates a new instance of the map value Collection container
* using the factory.
*
* This method can be overridden to perform your own processing
* instead of using the factory.
*
* @param size the collection size that is about to be added
* @return the new collection
*/
protected Collection createCollection(int size) {
return (Collection) collectionFactory.create();
}
//-----------------------------------------------------------------------
/**
* Inner class that provides the values view.
*/
private class Values extends AbstractCollection {
public Iterator iterator() {
final IteratorChain chain = new IteratorChain();
for (Iterator it = keySet().iterator(); it.hasNext();) {
chain.addIterator(new ValuesIterator(it.next()));
}
return chain;
}
public int size() {
return totalSize();
}
public void clear() {
MultiValueMap.this.clear();
}
}
/**
* Inner class that provides the values iterator.
*/
private class ValuesIterator implements Iterator {
private final Object key;
private final Collection values;
private final Iterator iterator;
public ValuesIterator(Object key) {
this.key = key;
this.values = getCollection(key);
this.iterator = values.iterator();
}
public void remove() {
iterator.remove();
if (values.isEmpty()) {
MultiValueMap.this.remove(key);
}
}
public boolean hasNext() {
return iterator.hasNext();
}
public Object next() {
return iterator.next();
}
}
/**
* Inner class that provides a simple reflection factory.
*/
private static class ReflectionFactory implements Factory {
private final Class clazz;
public ReflectionFactory(Class clazz) {
this.clazz = clazz;
}
public Object create() {
try {
return clazz.newInstance();
} catch (Exception ex) {
throw new FunctorException("Cannot instantiate class: " + clazz, ex);
}
}
}
}