/* * Copyright (C) 2005-2010 Alfresco Software Limited. * * This file is part of Alfresco * * Alfresco is free software: you can redistribute it and/or modify * it under the terms of the GNU Lesser General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * Alfresco is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public License * along with Alfresco. If not, see . */ package org.alfresco.repo.cache; import java.io.Serializable; import java.util.Collection; /** * Basic caching interface. *

* All implementations must be thread-safe. Additionally, the use of the * Serializable for both keys and values ensures that the underlying * cache implementations can support both clustered caches as well as persistent * caches. *

* All implementations must support null values. It therefore follows * that * 

 *    (simpleCache.contains(key) == true) does not imply (simpleCache.get(key) != null)
 *
* but * 
 *    (simpleCache.contains(key) == false) implies (simpleCache.get(key) == null)
 * 
 * 
 * @author Derek Hulley
 */
public interface SimpleCache
{
    /**
     * @param key       the cache key to check up on
     * @return          Returns true if there is a cache entry,
     *                  regardless of whether the value itself is null
     */
    public boolean contains(K key);
    
    public Collection getKeys();
    
    /**
     * @param key
     * @return          Returns the value associated with the key.  It will be null
     *                  if the value is null or if the cache doesn't have an entry.
     */
    public V get(K key);
    
    /**
     * @param key       the key against which to store the value
     * @param value     the value to store.  null is allowed.
     */
    public void put(K key, V value);
    
    /**
     * Removes the cache entry whether or not the value stored against it is null.
     * 
     * @param key       the key value to remove
     */
    public void remove(K key);
    
    public void clear();
}