001package org.apache.commons.jcs3.engine.memory.util;
002
003/*
004 * Licensed to the Apache Software Foundation (ASF) under one
005 * or more contributor license agreements.  See the NOTICE file
006 * distributed with this work for additional information
007 * regarding copyright ownership.  The ASF licenses this file
008 * to you under the Apache License, Version 2.0 (the
009 * "License"); you may not use this file except in compliance
010 * with the License.  You may obtain a copy of the License at
011 *
012 *   http://www.apache.org/licenses/LICENSE-2.0
013 *
014 * Unless required by applicable law or agreed to in writing,
015 * software distributed under the License is distributed on an
016 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
017 * KIND, either express or implied.  See the License for the
018 * specific language governing permissions and limitations
019 * under the License.
020 */
021
022import java.lang.ref.SoftReference;
023
024import org.apache.commons.jcs3.engine.behavior.ICacheElement;
025
026/**
027 * This wrapper is needed for double linked lists.
028 */
029public class SoftReferenceElementDescriptor<K, V>
030    extends MemoryElementDescriptor<K, V>
031{
032    /** Don't change */
033    private static final long serialVersionUID = -1905161209035522460L;
034
035    /** The CacheElement wrapped by this descriptor */
036    private transient final SoftReference<ICacheElement<K, V>> srce;
037
038    /**
039     * Constructs a usable MemoryElementDescriptor.
040     * <p>
041     * @param ce
042     */
043    public SoftReferenceElementDescriptor( final ICacheElement<K, V> ce )
044    {
045        super( null );
046        this.srce = new SoftReference<>(ce);
047    }
048
049    /**
050     * @return the ce
051     */
052    @Override
053    public ICacheElement<K, V> getCacheElement()
054    {
055        if (srce != null)
056        {
057            return srce.get();
058        }
059
060        return null;
061    }
062}