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This is the ehcache core module. Pair it with other modules for added functionality.
There is a newer version: 2.6.11
/**
 *  Copyright 2003-2010 Terracotta, Inc.
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package net.sf.ehcache.extension;

import net.sf.ehcache.CacheException;
import net.sf.ehcache.Ehcache;
import net.sf.ehcache.Status;

/**
 * This is a general purpose mechanism to allow generic extensions to a Cache.
 * 
 * CacheExtensions are tied into the Cache lifecycle. For that reason this interface has the
 *  lifecycle methods.
 * 

 * CacheExtensions are created using the CacheExtensionFactory which has a
 * createCacheCacheExtension() method which takes as a parameter a Cache and
 * properties. It can thus call back into any public method on Cache, including, of course,
 *  the load methods.
 * 

 * CacheExtensions are suitable for timing services, where you want to create a timer to
 * perform cache operations. The other way of adding Cache behaviour is to decorate a cache.
 * See {@link net.sf.ehcache.constructs.blocking.BlockingCache} for an example of how to do
 * this.
 * 

 * Because a CacheExtension holds a reference to a Cache, the CacheExtension can do things
 * such as registering a CacheEventListener or even a CacheManagerEventListener, all from
 * within a CacheExtension, creating more opportunities for customisation.
 *
 * @author Greg Luck
 * @version $Id: CacheExtension.java 2154 2010-04-06 02:45:52Z cdennis $
 */
public interface CacheExtension {

    /**
     * Notifies providers to initialise themselves.
     * 

     * This method is called during the Cache's initialise method after it has changed it's
     * status to alive. Cache operations are legal in this method.
     *
     * @throws CacheException
     */
    void init();

    /**
     * Providers may be doing all sorts of exotic things and need to be able to clean up on
     * dispose.
     * 

     * Cache operations are illegal when this method is called. The cache itself is partly
     * disposed when this method is called.
     *
     * @throws CacheException
     */
    void dispose() throws CacheException;

    /**
     * Creates a clone of this extension. This method will only be called by ehcache before a
     * cache is initialized.
     * 
     * Implementations should throw CloneNotSupportedException if they do not support clone
     * but that will stop them from being used with defaultCache.
     *
     * @param cache the cache extended
     * @return a clone
     * @throws CloneNotSupportedException if the extension could not be cloned.
     */
    public CacheExtension clone(Ehcache cache) throws CloneNotSupportedException;


    /**
     * @return the status of the extension
     */
    public Status getStatus();
}