/*
* Copyright (c) 2003 The Visigoth Software Society. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution, if
* any, must include the following acknowledgement:
* "This product includes software developed by the
* Visigoth Software Society (http://www.visigoths.org/)."
* Alternately, this acknowledgement may appear in the software itself,
* if and wherever such third-party acknowledgements normally appear.
*
* 4. Neither the name "FreeMarker", "Visigoth", nor any of the names of the
* project contributors may be used to endorse or promote products derived
* from this software without prior written permission. For written
* permission, please contact [email protected].
*
* 5. Products derived from this software may not be called "FreeMarker" or "Visigoth"
* nor may "FreeMarker" or "Visigoth" appear in their names
* without prior written permission of the Visigoth Software Society.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE VISIGOTH SOFTWARE SOCIETY OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Visigoth Software Society. For more
* information on the Visigoth Software Society, please see
* http://www.visigoths.org/
*/
package freemarker.cache;
import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.SoftReference;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Map;
import freemarker.template.utility.UndeclaredThrowableException;
/**
* Soft cache storage is a cache storage that uses {@link SoftReference}
* objects to hold the objects it was passed, therefore allows the garbage
* collector to purge the cache when it determines that it wants to free up
* memory.
* This class is thread-safe to the extent that its underlying map is. The
* default implementation uses a concurrent map on Java 5 and above, so it is
* thread-safe in that case.
* @author Attila Szegedi
* @version $Id: SoftCacheStorage.java,v 1.4 2003/09/22 20:47:03 ddekany Exp $
*
*/
public class SoftCacheStorage implements ConcurrentCacheStorage
{
private static final Method atomicRemove = getAtomicRemoveMethod();
private final ReferenceQueue queue = new ReferenceQueue();
private final Map map;
private final boolean concurrent;
public SoftCacheStorage() {
this(ConcurrentMapFactory.createMap());
}
public boolean isConcurrent() {
return concurrent;
}
public SoftCacheStorage(Map backingMap) {
map = backingMap;
this.concurrent = ConcurrentMapFactory.isConcurrent(map);
}
public Object get(Object key) {
processQueue();
Reference ref = (Reference)map.get(key);
return ref == null ? null : ref.get();
}
public void put(Object key, Object value) {
processQueue();
map.put(key, new SoftValueReference(key, value, queue));
}
public void remove(Object key) {
processQueue();
map.remove(key);
}
public void clear() {
map.clear();
processQueue();
}
private void processQueue() {
for(;;) {
SoftValueReference ref = (SoftValueReference)queue.poll();
if(ref == null) {
return;
}
Object key = ref.getKey();
if(concurrent) {
try {
atomicRemove.invoke(map, new Object[] { key, ref });
}
catch(IllegalAccessException e) {
throw new UndeclaredThrowableException(e);
}
catch(InvocationTargetException e) {
throw new UndeclaredThrowableException(e);
}
}
else if(map.get(key) == ref) {
map.remove(key);
}
}
}
private static final class SoftValueReference extends SoftReference {
private final Object key;
SoftValueReference(Object key, Object value, ReferenceQueue queue) {
super(value, queue);
this.key = key;
}
Object getKey() {
return key;
}
}
private static Method getAtomicRemoveMethod() {
try {
return Class.forName("java.util.concurrent.ConcurrentMap").getMethod("remove", new Class[] { Object.class, Object.class });
}
catch(ClassNotFoundException e) {
return null;
}
catch(NoSuchMethodException e) {
throw new UndeclaredThrowableException(e);
}
}
}
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