oracle.toplink.essentials.internal.identitymaps.SoftCacheWeakIdentityMap Maven / Gradle / Ivy
/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
*
* // Copyright (c) 1998, 2007, Oracle. All rights reserved.
*
*
* The contents of this file are subject to the terms of either the GNU
* General Public License Version 2 only ("GPL") or the Common Development
* and Distribution License("CDDL") (collectively, the "License"). You
* may not use this file except in compliance with the License. You can obtain
* a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
* or glassfish/bootstrap/legal/LICENSE.txt. See the License for the specific
* language governing permissions and limitations under the License.
*
* When distributing the software, include this License Header Notice in each
* file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
* Sun designates this particular file as subject to the "Classpath" exception
* as provided by Sun in the GPL Version 2 section of the License file that
* accompanied this code. If applicable, add the following below the License
* Header, with the fields enclosed by brackets [] replaced by your own
* identifying information: "Portions Copyrighted [year]
* [name of copyright owner]"
*
* Contributor(s):
*
* If you wish your version of this file to be governed by only the CDDL or
* only the GPL Version 2, indicate your decision by adding "[Contributor]
* elects to include this software in this distribution under the [CDDL or GPL
* Version 2] license." If you don't indicate a single choice of license, a
* recipient has the option to distribute your version of this file under
* either the CDDL, the GPL Version 2 or to extend the choice of license to
* its licensees as provided above. However, if you add GPL Version 2 code
* and therefore, elected the GPL Version 2 license, then the option applies
* only if the new code is made subject to such option by the copyright
* holder.
*/
package oracle.toplink.essentials.internal.identitymaps;
import java.lang.ref.*;
/**
* Purpose: A weak cache is identical to the weak identity map, however the weak
* can be a performance problem for some types of apps because it can cause too much garbage collection
* of objects read causing them to be re-read and re-built (this defeats the purpose of the cache).
* The weak cache solves this through also holding a fixed number of objects is memory to improve caching.
*
Responsibilities:
* - Guarantees identity
*
- Allows garbage collection
*
- Increases performance through maintaining a fixed size cache of MRU objects when memory is available
*
- The default size of the reference cache is half the max size
*
* @since TOPLink/Java 1.2
*/
public class SoftCacheWeakIdentityMap extends HardCacheWeakIdentityMap {
public SoftCacheWeakIdentityMap(int size) {
super(size);
}
/**
* Creates a Soft reference if Required
* @param object is the domain object to cache.
*/
public Object buildReference(Object object) {
return new SoftReference(object);
}
/**
* Checks if the object is null, or reference's object is null.
* @param the object for hard or the reference for soft.
*/
public boolean hasReference(Object reference) {
return (reference != null) && (((SoftReference)reference).get() != null);
}
}