/*
* 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.ext.util;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.SoftReference;
import java.util.Map;
import freemarker.template.TemplateModel;
import freemarker.template.TemplateModelAdapter;
/**
* Internally used by various wrapper implementations to implement model
* caching.
* @version $Id: ModelCache.java,v 1.9 2003/01/12 23:40:15 revusky Exp $
* @author Attila Szegedi
*/
public abstract class ModelCache
{
private boolean useCache = false;
private Map modelCache = null;
private ReferenceQueue refQueue = null;
protected ModelCache()
{
}
/**
* Sets whether this wrapper caches model instances. Default is false.
* When set to true, calling {@link #getInstance(Object)}
* multiple times for the same object will return the same model.
*/
public synchronized void setUseCache(boolean useCache)
{
this.useCache = useCache;
if(useCache)
{
modelCache = new IdentityHashMap();
refQueue = new ReferenceQueue();
}
else
{
modelCache = null;
refQueue = null;
}
}
public TemplateModel getInstance(Object object)
{
if(object instanceof TemplateModel) {
return (TemplateModel)object;
}
if(object instanceof TemplateModelAdapter) {
return ((TemplateModelAdapter)object).getTemplateModel();
}
if(useCache && isCacheable(object)) {
TemplateModel model = lookup(object);
if(model == null) {
model = create(object);
register(model, object);
}
return model;
}
else {
return create(object);
}
}
protected abstract TemplateModel create(Object object);
protected abstract boolean isCacheable(Object object);
public void clearCache()
{
if(modelCache != null)
{
synchronized(modelCache)
{
modelCache.clear();
}
}
}
private final TemplateModel lookup(Object object)
{
ModelReference ref = null;
// NOTE: we're doing minimal synchronizations -- which can lead to
// duplicate wrapper creation. However, this has no harmful side-effects and
// is a lesser performance hit.
synchronized (modelCache)
{
ref = (ModelReference) modelCache.get(object);
}
if (ref != null)
return ref.getModel();
return null;
}
private final void register(TemplateModel model, Object object)
{
synchronized (modelCache) {
// Remove cleared references
for (;;) {
ModelReference queuedRef = (ModelReference) refQueue.poll();
if (queuedRef == null)
break;
modelCache.remove(queuedRef.object);
}
// Register new reference
modelCache.put(object, new ModelReference(model, object, refQueue));
}
}
/**
* A special soft reference that is registered in the modelCache.
* When it gets cleared (that is, the model became unreachable)
* it will remove itself from the model cache.
*/
private static final class ModelReference extends SoftReference
{
Object object;
ModelReference(TemplateModel ref, Object object, ReferenceQueue refQueue)
{
super(ref, refQueue);
this.object = object;
}
TemplateModel getModel()
{
return (TemplateModel) this.get();
}
}
}
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