/******************************************************************************* | |
* Copyright (c) 1998, 2013 Oracle and/or its affiliates. All rights reserved. | |
* This program and the accompanying materials are made available under the | |
* terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0 | |
* which accompanies this distribution. | |
* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html | |
* and the Eclipse Distribution License is available at | |
* http://www.eclipse.org/org/documents/edl-v10.php. | |
* | |
* Contributors: | |
* Oracle - initial API and implementation from Oracle TopLink | |
******************************************************************************/ | |
package org.eclipse.persistence.config; | |
/** | |
* Cache type persistence property values. | |
* The cache type defines the type of cache usage for the entities. | |
* Its usage depends on the memory and caching requirements of the entity. | |
* If no caching is desired at all the PersistenceUnitProperties.CACHE_SHARED_ should | |
* instead be used. | |
* | |
* <p>JPA persistence property Usage: | |
* | |
* <p>for all entities append DEFAULT suffix to CACHE_TYPE_ prefix: | |
* <p><code>properties.add(PersistenceUnitProperties.CACHE_TYPE_DEFAULT, CacheType.Weak);</code> | |
* | |
* <p>for a single entity append either entity name or a full class name to CACHE_TYPE_ prefix: | |
* <p><code>properties.add(PersistenceUnitProperties.CACHE_TYPE_ + "Employee", CacheType.Weak);</code> | |
* <p><code>properties.add(PersistenceUnitProperties.CACHE_TYPE_ + "my.test.Employee", CacheType.Weak);</code> | |
* | |
* <p>Values are case-insensitive. | |
* "" could be used instead of default value CacheType.DEFAULT. | |
* | |
* @see PersistenceUnitProperties#CACHE_SHARED_ | |
* @see PersistenceUnitProperties#CACHE_TYPE_ | |
*/ | |
public class CacheType { | |
/** | |
* A Weak cache holds all objects in use by the application, | |
* but allows any un-referenced objects to be free to garbage collection. | |
* This guarantees object identity, allows optimal garbage collection, but provides little caching benefit. | |
*/ | |
public static final String Weak = "Weak"; | |
/** | |
* A Soft cache holds all objects read by the application, | |
* but allows any un-referenced objects to be free to garbage collection only when the JVM decides memory is low. | |
* This guarantees object identity, allows garbage collection when memory is low, and provides optimal caching benefit. | |
*/ | |
public static final String Soft = "Soft"; | |
/** | |
* A SoftWeak cache holds all objects in use by the application, | |
* and a fixed size sub-cache of MRU objects using Soft references. | |
* It allows any un-referenced objects not in the sub-cache to be free to garbage collection, | |
* and the objects in the sub-cache are free to garbage collect only when the JVM decides memory is low. | |
* This guarantees object identity, allows configurable garbage collection, and provides configurable caching benefit. | |
*/ | |
public static final String SoftWeak = "SoftWeak"; | |
/** | |
* A HardWeak cache holds all objects in use by the application, | |
* and a fixed size sub-cache of MRU objects using normal (hard) references. | |
* It allows any un-referenced objects not in the sub-cache to be free to garbage collection, | |
* but not objects in the sub-cache. | |
* This guarantees object identity, allows configurable garbage collection, and provides configurable caching benefit. | |
*/ | |
public static final String HardWeak = "HardWeak"; | |
/** | |
* A Soft cache holds all objects read by the application. | |
* It does not allow any garbage collection. * | |
* This guarantees object identity, allows no garbage collection, and provides complete caching benefit. | |
* <p>WARNING: This cache type should only be used for a fixed sized number of objects, | |
* otherwise it will lead to an eventual memory leak. | |
*/ | |
public static final String Full = "Full"; | |
/** | |
* NONE does not cache any objects. | |
* It allows any un-referenced objects to be free to garbage collection. | |
* This provides no object identity, allows complete garbage collection, and provides no caching benefit. | |
* <p>WARNING: This cache type should normally not be used. Instead disable the share cache through PersistenceUnitProperties.CACHE_SHARED_. | |
* Lack of object identity can lead to infinite loops for objects that have circular references and no indirection. | |
* @see PersistenceUnitProperties#CACHE_SHARED_ | |
*/ | |
public static final String NONE = "NONE"; | |
/** | |
* The default cache type is SoftWeak. | |
*/ | |
public static final String DEFAULT = SoftWeak; | |
} |