001/*
002 * This library is part of OpenCms -
003 * The Open Source Content Management System
004 *
005 * Copyright (c) Alkacon Software GmbH & Co. KG (https://www.alkacon.com)
006 *
007 * This library is free software; you can redistribute it and/or
008 * modify it under the terms of the GNU Lesser General Public
009 * License as published by the Free Software Foundation; either
010 * version 2.1 of the License, or (at your option) any later version.
011 *
012 * This library is distributed in the hope that it will be useful,
013 * but WITHOUT ANY WARRANTY; without even the implied warranty of
014 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
015 * Lesser General Public License for more details.
016 *
017 * For further information about Alkacon Software GmbH & Co. KG, please see the
018 * company website: https://www.alkacon.com
019 *
020 * For further information about OpenCms, please see the
021 * project website: https://www.opencms.org
022 *
023 * You should have received a copy of the GNU Lesser General Public
024 * License along with this library; if not, write to the Free Software
025 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
026 */
027
028package org.opencms.loader.imagecache;
029
030import java.time.Instant;
031import java.util.Objects;
032
033/**
034 * Backend-neutral metadata for an image cache entry.<p>
035 */
036public final class CmsImageCacheEntry {
037
038    /** The cache key. */
039    private final String m_key;
040
041    /** The entry length. */
042    private final long m_length;
043
044    /** The last modification time, if available. */
045    private final Instant m_lastModified;
046
047    /** An optional opaque backend revision. */
048    private final String m_revision;
049
050    /**
051     * Creates an image cache entry.<p>
052     *
053     * @param key the cache key
054     * @param length the entry length
055     * @param lastModified the last modification time, or {@code null}
056     * @param revision an opaque backend revision, or {@code null}
057     */
058    public CmsImageCacheEntry(String key, long length, Instant lastModified, String revision) {
059
060        m_key = Objects.requireNonNull(key, "key");
061        if (key.isEmpty()) {
062            throw new IllegalArgumentException("The image cache entry key must not be empty.");
063        }
064        if (length < 0) {
065            throw new IllegalArgumentException("The image cache entry length must not be negative.");
066        }
067        m_length = length;
068        m_lastModified = lastModified;
069        m_revision = revision;
070    }
071
072    /**
073     * Returns the cache key.<p>
074     *
075     * @return the cache key
076     */
077    public String getKey() {
078
079        return m_key;
080    }
081
082    /**
083     * Returns the last modification time.<p>
084     *
085     * @return the last modification time, or {@code null}
086     */
087    public Instant getLastModified() {
088
089        return m_lastModified;
090    }
091
092    /**
093     * Returns the entry length.<p>
094     *
095     * @return the entry length
096     */
097    public long getLength() {
098
099        return m_length;
100    }
101
102    /**
103     * Returns the opaque backend revision.<p>
104     *
105     * @return the backend revision, or {@code null}
106     */
107    public String getRevision() {
108
109        return m_revision;
110    }
111}