oracle.toplink.essentials.internal.identitymaps.SoftCacheWeakIdentityMap Maven / Gradle / Ivy
/*
* The contents of this file are subject to the terms
* of the Common Development and Distribution License
* (the "License"). You may not use this file except
* in compliance with the License.
*
* You can obtain a copy of the license at
* glassfish/bootstrap/legal/CDDLv1.0.txt or
* https://glassfish.dev.java.net/public/CDDLv1.0.html.
* See the License for the specific language governing
* permissions and limitations under the License.
*
* When distributing Covered Code, include this CDDL
* HEADER in each file and include the License file at
* glassfish/bootstrap/legal/CDDLv1.0.txt. If applicable,
* add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your
* own identifying information: Portions Copyright [yyyy]
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*/
// Copyright (c) 1998, 2007, Oracle. All rights reserved.
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);
}
}