001/**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.activemq.memory;
018
019/**
020 * Defines the interface used to cache messages.
021 * 
022 * 
023 */
024public interface Cache {
025
026    /**
027     * Gets an object that was previously <code>put</code> into this object.
028     * 
029     * @param msgid
030     * @return null if the object was not previously put or if the object has
031     *         expired out of the cache.
032     */
033    Object get(Object key);
034
035    /**
036     * Puts an object into the cache.
037     * 
038     * @param messageID
039     * @param message
040     */
041    Object put(Object key, Object value);
042
043    /**
044     * Removes an object from the cache.
045     * 
046     * @param messageID
047     * @return the object associated with the key if it was still in the cache.
048     */
049    Object remove(Object key);
050
051    /**
052     * Lets a cache know it will not be used any further and that it can release
053     * acquired resources
054     */
055    void close();
056
057    /**
058     * How big is the cache right now?
059     * 
060     * @return
061     */
062    int size();
063
064}