org.apache.commons.beanutils.WeakFastHashMap Maven / Gradle / Ivy
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This artifact provides a single jar that contains all classes required to use remote EJB and JMS, including
all dependencies. It is intended for use by those not using maven, maven users should just import the EJB and
JMS BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up
with different versions on classes on the class path).
/*
* 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.beanutils;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.WeakHashMap;
/**
* A customized implementation of java.util.HashMap designed
* to operate in a multithreaded environment where the large majority of
* method calls are read-only, instead of structural changes. When operating
* in "fast" mode, read calls are non-synchronized and write calls perform the
* following steps:
*
* - Clone the existing collection
*
- Perform the modification on the clone
*
- Replace the existing collection with the (modified) clone
*
* When first created, objects of this class default to "slow" mode, where
* all accesses of any type are synchronized but no cloning takes place. This
* is appropriate for initially populating the collection, followed by a switch
* to "fast" mode (by calling setFast(true)) after initialization
* is complete.
*
* NOTE: If you are creating and accessing a
* HashMap only within a single thread, you should use
* java.util.HashMap directly (with no synchronization), for
* maximum performance.
*
* NOTE: This class is not cross-platform.
* Using it may cause unexpected failures on some architectures.
* It suffers from the same problems as the double-checked locking idiom.
* In particular, the instruction that clones the internal collection and the
* instruction that sets the internal reference to the clone can be executed
* or perceived out-of-order. This means that any read operation might fail
* unexpectedly, as it may be reading the state of the internal collection
* before the internal collection is fully formed.
* For more information on the double-checked locking idiom, see the
*
* Double-Checked Locking Idiom Is Broken Declaration.
*
* @since Commons Collections 1.0
* @version $Id$
*/
class WeakFastHashMap extends HashMap {
/**
* The underlying map we are managing.
*/
private Map map = null;
/**
* Are we currently operating in "fast" mode?
*/
private boolean fast = false;
// Constructors
// ----------------------------------------------------------------------
/**
* Construct an empty map.
*/
public WeakFastHashMap() {
super();
this.map = createMap();
}
/**
* Construct an empty map with the specified capacity.
*
* @param capacity the initial capacity of the empty map
*/
public WeakFastHashMap(final int capacity) {
super();
this.map = createMap(capacity);
}
/**
* Construct an empty map with the specified capacity and load factor.
*
* @param capacity the initial capacity of the empty map
* @param factor the load factor of the new map
*/
public WeakFastHashMap(final int capacity, final float factor) {
super();
this.map = createMap(capacity, factor);
}
/**
* Construct a new map with the same mappings as the specified map.
*
* @param map the map whose mappings are to be copied
*/
public WeakFastHashMap(final Map map) {
super();
this.map = createMap(map);
}
// Property access
// ----------------------------------------------------------------------
/**
* Returns true if this map is operating in fast mode.
*
* @return true if this map is operating in fast mode
*/
public boolean getFast() {
return (this.fast);
}
/**
* Sets whether this map is operating in fast mode.
*
* @param fast true if this map should operate in fast mode
*/
public void setFast(final boolean fast) {
this.fast = fast;
}
// Map access
// ----------------------------------------------------------------------
// These methods can forward straight to the wrapped Map in 'fast' mode.
// (because they are query methods)
/**
* Return the value to which this map maps the specified key. Returns
* null if the map contains no mapping for this key, or if
* there is a mapping with a value of null. Use the
* containsKey() method to disambiguate these cases.
*
* @param key the key whose value is to be returned
* @return the value mapped to that key, or null
*/
@Override
public V get(final Object key) {
if (fast) {
return (map.get(key));
} else {
synchronized (map) {
return (map.get(key));
}
}
}
/**
* Return the number of key-value mappings in this map.
*
* @return the current size of the map
*/
@Override
public int size() {
if (fast) {
return (map.size());
} else {
synchronized (map) {
return (map.size());
}
}
}
/**
* Return true if this map contains no mappings.
*
* @return is the map currently empty
*/
@Override
public boolean isEmpty() {
if (fast) {
return (map.isEmpty());
} else {
synchronized (map) {
return (map.isEmpty());
}
}
}
/**
* Return true if this map contains a mapping for the
* specified key.
*
* @param key the key to be searched for
* @return true if the map contains the key
*/
@Override
public boolean containsKey(final Object key) {
if (fast) {
return (map.containsKey(key));
} else {
synchronized (map) {
return (map.containsKey(key));
}
}
}
/**
* Return true if this map contains one or more keys mapping
* to the specified value.
*
* @param value the value to be searched for
* @return true if the map contains the value
*/
@Override
public boolean containsValue(final Object value) {
if (fast) {
return (map.containsValue(value));
} else {
synchronized (map) {
return (map.containsValue(value));
}
}
}
// Map modification
// ----------------------------------------------------------------------
// These methods perform special behaviour in 'fast' mode.
// The map is cloned, updated and then assigned back.
// See the comments at the top as to why this won't always work.
/**
* Associate the specified value with the specified key in this map.
* If the map previously contained a mapping for this key, the old
* value is replaced and returned.
*
* @param key the key with which the value is to be associated
* @param value the value to be associated with this key
* @return the value previously mapped to the key, or null
*/
@Override
public V put(final K key, final V value) {
if (fast) {
synchronized (this) {
final Map temp = cloneMap(map);
final V result = temp.put(key, value);
map = temp;
return (result);
}
} else {
synchronized (map) {
return (map.put(key, value));
}
}
}
/**
* Copy all of the mappings from the specified map to this one, replacing
* any mappings with the same keys.
*
* @param in the map whose mappings are to be copied
*/
@Override
public void putAll(final Map in) {
if (fast) {
synchronized (this) {
final Map temp = cloneMap(map);
temp.putAll(in);
map = temp;
}
} else {
synchronized (map) {
map.putAll(in);
}
}
}
/**
* Remove any mapping for this key, and return any previously
* mapped value.
*
* @param key the key whose mapping is to be removed
* @return the value removed, or null
*/
@Override
public V remove(final Object key) {
if (fast) {
synchronized (this) {
final Map temp = cloneMap(map);
final V result = temp.remove(key);
map = temp;
return (result);
}
} else {
synchronized (map) {
return (map.remove(key));
}
}
}
/**
* Remove all mappings from this map.
*/
@Override
public void clear() {
if (fast) {
synchronized (this) {
map = createMap();
}
} else {
synchronized (map) {
map.clear();
}
}
}
// Basic object methods
// ----------------------------------------------------------------------
/**
* Compare the specified object with this list for equality. This
* implementation uses exactly the code that is used to define the
* list equals function in the documentation for the
* Map.equals method.
*
* @param o the object to be compared to this list
* @return true if the two maps are equal
*/
@Override
public boolean equals(final Object o) {
// Simple tests that require no synchronization
if (o == this) {
return (true);
} else if (!(o instanceof Map)) {
return (false);
}
final Map mo = (Map) o;
// Compare the two maps for equality
if (fast) {
if (mo.size() != map.size()) {
return (false);
}
for (final Map.Entry e : map.entrySet()) {
final K key = e.getKey();
final V value = e.getValue();
if (value == null) {
if (!(mo.get(key) == null && mo.containsKey(key))) {
return (false);
}
} else {
if (!value.equals(mo.get(key))) {
return (false);
}
}
}
return (true);
} else {
synchronized (map) {
if (mo.size() != map.size()) {
return (false);
}
for (final Map.Entry e : map.entrySet()) {
final K key = e.getKey();
final V value = e.getValue();
if (value == null) {
if (!(mo.get(key) == null && mo.containsKey(key))) {
return (false);
}
} else {
if (!value.equals(mo.get(key))) {
return (false);
}
}
}
return (true);
}
}
}
/**
* Return the hash code value for this map. This implementation uses
* exactly the code that is used to define the list hash function in the
* documentation for the Map.hashCode method.
*
* @return suitable integer hash code
*/
@Override
public int hashCode() {
if (fast) {
int h = 0;
for (final Map.Entry e : map.entrySet()) {
h += e.hashCode();
}
return (h);
} else {
synchronized (map) {
int h = 0;
for (final Map.Entry e : map.entrySet()) {
h += e.hashCode();
}
return (h);
}
}
}
/**
* Return a shallow copy of this FastHashMap instance.
* The keys and values themselves are not copied.
*
* @return a clone of this map
*/
@Override
public Object clone() {
WeakFastHashMap results = null;
if (fast) {
results = new WeakFastHashMap(map);
} else {
synchronized (map) {
results = new WeakFastHashMap(map);
}
}
results.setFast(getFast());
return (results);
}
// Map views
// ----------------------------------------------------------------------
/**
* Return a collection view of the mappings contained in this map. Each
* element in the returned collection is a Map.Entry.
* @return the set of map Map entries
*/
@Override
public Set> entrySet() {
return new EntrySet();
}
/**
* Return a set view of the keys contained in this map.
* @return the set of the Map's keys
*/
@Override
public Set keySet() {
return new KeySet();
}
/**
* Return a collection view of the values contained in this map.
* @return the set of the Map's values
*/
@Override
public Collection values() {
return new Values();
}
// Abstractions on Map creations (for subclasses such as WeakFastHashMap)
// ----------------------------------------------------------------------
protected Map createMap() {
return new WeakHashMap();
}
protected Map createMap(final int capacity) {
return new WeakHashMap(capacity);
}
protected Map createMap(final int capacity, final float factor) {
return new WeakHashMap(capacity, factor);
}
protected Map createMap(final Map map) {
return new WeakHashMap(map);
}
protected Map cloneMap(final Map map) {
return createMap(map);
}
// Map view inner classes
// ----------------------------------------------------------------------
/**
* Abstract collection implementation shared by keySet(), values() and entrySet().
*
* @param the element type
*/
private abstract class CollectionView implements Collection {
public CollectionView() {
}
protected abstract Collection get(Map map);
protected abstract E iteratorNext(Map.Entry entry);
public void clear() {
if (fast) {
synchronized (WeakFastHashMap.this) {
map = createMap();
}
} else {
synchronized (map) {
get(map).clear();
}
}
}
public boolean remove(final Object o) {
if (fast) {
synchronized (WeakFastHashMap.this) {
final Map temp = cloneMap(map);
final boolean r = get(temp).remove(o);
map = temp;
return r;
}
} else {
synchronized (map) {
return get(map).remove(o);
}
}
}
public boolean removeAll(final Collection o) {
if (fast) {
synchronized (WeakFastHashMap.this) {
final Map temp = cloneMap(map);
final boolean r = get(temp).removeAll(o);
map = temp;
return r;
}
} else {
synchronized (map) {
return get(map).removeAll(o);
}
}
}
public boolean retainAll(final Collection o) {
if (fast) {
synchronized (WeakFastHashMap.this) {
final Map temp = cloneMap(map);
final boolean r = get(temp).retainAll(o);
map = temp;
return r;
}
} else {
synchronized (map) {
return get(map).retainAll(o);
}
}
}
public int size() {
if (fast) {
return get(map).size();
} else {
synchronized (map) {
return get(map).size();
}
}
}
public boolean isEmpty() {
if (fast) {
return get(map).isEmpty();
} else {
synchronized (map) {
return get(map).isEmpty();
}
}
}
public boolean contains(final Object o) {
if (fast) {
return get(map).contains(o);
} else {
synchronized (map) {
return get(map).contains(o);
}
}
}
public boolean containsAll(final Collection o) {
if (fast) {
return get(map).containsAll(o);
} else {
synchronized (map) {
return get(map).containsAll(o);
}
}
}
public T[] toArray(final T[] o) {
if (fast) {
return get(map).toArray(o);
} else {
synchronized (map) {
return get(map).toArray(o);
}
}
}
public Object[] toArray() {
if (fast) {
return get(map).toArray();
} else {
synchronized (map) {
return get(map).toArray();
}
}
}
@Override
public boolean equals(final Object o) {
if (o == this) {
return true;
}
if (fast) {
return get(map).equals(o);
} else {
synchronized (map) {
return get(map).equals(o);
}
}
}
@Override
public int hashCode() {
if (fast) {
return get(map).hashCode();
} else {
synchronized (map) {
return get(map).hashCode();
}
}
}
public boolean add(final E o) {
throw new UnsupportedOperationException();
}
public boolean addAll(final Collection c) {
throw new UnsupportedOperationException();
}
public Iterator iterator() {
return new CollectionViewIterator();
}
private class CollectionViewIterator implements Iterator {
private Map expected;
private Map.Entry lastReturned = null;
private final Iterator> iterator;
public CollectionViewIterator() {
this.expected = map;
this.iterator = expected.entrySet().iterator();
}
public boolean hasNext() {
if (expected != map) {
throw new ConcurrentModificationException();
}
return iterator.hasNext();
}
public E next() {
if (expected != map) {
throw new ConcurrentModificationException();
}
lastReturned = iterator.next();
return iteratorNext(lastReturned);
}
public void remove() {
if (lastReturned == null) {
throw new IllegalStateException();
}
if (fast) {
synchronized (WeakFastHashMap.this) {
if (expected != map) {
throw new ConcurrentModificationException();
}
WeakFastHashMap.this.remove(lastReturned.getKey());
lastReturned = null;
expected = map;
}
} else {
iterator.remove();
lastReturned = null;
}
}
}
}
/**
* Set implementation over the keys of the FastHashMap
*/
private class KeySet extends CollectionView implements Set {
@Override
protected Collection get(final Map map) {
return map.keySet();
}
@Override
protected K iteratorNext(final Map.Entry entry) {
return entry.getKey();
}
}
/**
* Collection implementation over the values of the FastHashMap
*/
private class Values extends CollectionView {
@Override
protected Collection get(final Map map) {
return map.values();
}
@Override
protected V iteratorNext(final Map.Entry entry) {
return entry.getValue();
}
}
/**
* Set implementation over the entries of the FastHashMap
*/
private class EntrySet extends CollectionView> implements Set> {
@Override
protected Collection> get(final Map map) {
return map.entrySet();
}
@Override
protected Map.Entry iteratorNext(final Map.Entry entry) {
return entry;
}
}
}