| /* |
| * 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 visigoths@visigoths.org. |
| * |
| * 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. |
| * @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(); |
| } |
| } |
| |
| } |