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.commons.pool2.impl;
018
019import java.lang.ref.SoftReference;
020
021/**
022 * Extension of {@link DefaultPooledObject} to wrap pooled soft references.
023 *
024 * <p>This class is intended to be thread-safe.</p>
025 *
026 * @param <T> the type of the underlying object that the wrapped SoftReference
027 * refers to.
028 *
029 * @version $Revision: $
030 *
031 * @since 2.0
032 */
033public class PooledSoftReference<T> extends DefaultPooledObject<T> {
034
035    /** SoftReference wrapped by this object */
036    private volatile SoftReference<T> reference;
037
038    /**
039     * Creates a new PooledSoftReference wrapping the provided reference.
040     *
041     * @param reference SoftReference to be managed by the pool
042     */
043    public PooledSoftReference(SoftReference<T> reference) {
044        super(null);  // Null the hard reference in the parent
045        this.reference = reference;
046    }
047
048    /**
049     * Returns the object that the wrapped SoftReference refers to.
050     * <p>
051     * Note that if the reference has been cleared, this method will return
052     * null.
053     *
054     * @return Object referred to by the SoftReference
055     */
056    @Override
057    public T getObject() {
058        return reference.get();
059    }
060
061    /**
062     * {@inheritDoc}
063     */
064    @Override
065    public String toString() {
066        StringBuilder result = new StringBuilder();
067        result.append("Referenced Object: ");
068        result.append(getObject().toString());
069        result.append(", State: ");
070        synchronized (this) {
071            result.append(getState().toString());
072        }
073        return result.toString();
074        // TODO add other attributes
075        // TODO encapsulate state and other attribute display in parent
076    }
077
078    /**
079     * Returns the SoftReference wrapped by this object.
080     *
081     * @return underlying SoftReference
082     */
083    public synchronized SoftReference<T> getReference() {
084        return reference;
085    }
086
087    /**
088     * Sets the wrapped reference.
089     *
090     * <p>This method exists to allow a new, non-registered reference to be
091     * held by the pool to track objects that have been checked out of the pool.
092     * The actual parameter <strong>should</strong> be a reference to the same
093     * object that {@link #getObject()} returns before calling this method.</p>
094     *
095     * @param reference new reference
096     */
097    public synchronized void setReference(SoftReference<T> reference) {
098        this.reference = reference;
099    }
100}