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    import java.util.concurrent.atomic.AtomicLong;
020    import org.apache.activemq.usage.MemoryUsage;
021    
022    /**
023     * Simple CacheFilter that increases/decreases usage on a UsageManager as
024     * objects are added/removed from the Cache.
025     * 
026     * 
027     */
028    public class UsageManagerCacheFilter extends CacheFilter {
029    
030        private final AtomicLong totalUsage = new AtomicLong(0);
031        private final MemoryUsage usage;
032    
033        public UsageManagerCacheFilter(Cache next, MemoryUsage um) {
034            super(next);
035            this.usage = um;
036        }
037    
038        public Object put(Object key, Object value) {
039            long usageValue = getUsageOfAddedObject(value);
040            Object rc = super.put(key, value);
041            if (rc != null) {
042                usageValue -= getUsageOfRemovedObject(rc);
043            }
044            totalUsage.addAndGet(usageValue);
045            usage.increaseUsage(usageValue);
046            return rc;
047        }
048    
049        public Object remove(Object key) {
050            Object rc = super.remove(key);
051            if (rc != null) {
052                long usageValue = getUsageOfRemovedObject(rc);
053                totalUsage.addAndGet(-usageValue);
054                usage.decreaseUsage(usageValue);
055            }
056            return rc;
057        }
058    
059        protected long getUsageOfAddedObject(Object value) {
060            return 1;
061        }
062    
063        protected long getUsageOfRemovedObject(Object value) {
064            return 1;
065        }
066    
067        public void close() {
068            usage.decreaseUsage(totalUsage.get());
069        }
070    }