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
019import java.util.concurrent.atomic.AtomicLong;
020import 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 */
028public 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}