CacheRefresher.java

/**********************************************************************************
 * $URL: https://source.sakaiproject.org/svn/kernel/trunk/api/src/main/java/org/sakaiproject/memory/api/CacheRefresher.java $
 * $Id: CacheRefresher.java 105077 2012-02-24 22:54:29Z ottenhoff@longsight.com $
 ***********************************************************************************
 *
 * Copyright (c) 2003, 2004, 2005, 2006, 2008 Sakai Foundation
 *
 * Licensed under the Educational Community 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.opensource.org/licenses/ECL-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 org.sakaiproject.memory.api;

import org.sakaiproject.event.api.Event;

/**
 * <p>
 * Utility API for classes that will refresh a cache entry when expired.
 * </p>
 */
public interface CacheRefresher
{
	/**
	 * Get a new value for this key whose value has already expired in the cache.
	 * 
	 * @param key
	 *        The key whose value has expired and needs to be refreshed.
	 * @param oldValue
	 *        The old exipred value of the key.
	 * @param event
	 *        The event which triggered this refresh.
	 * @return a new value for use in the cache for this key; if null, the entry will be removed.
	 */
	public Object refresh(Object key, Object oldValue, Event event);
}