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     */
017    package org.apache.activemq.memory;
018    
019    /**
020     * Defines the interface used to cache messages.
021     * 
022     * 
023     */
024    public 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    }