001/*
002 * This library is part of OpenCms -
003 * the Open Source Content Management System
004 *
005 * Copyright (c) Alkacon Software GmbH & Co. KG (http://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: http://www.alkacon.com
019 *
020 * For further information about OpenCms, please see the
021 * project website: http://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.cache;
029
030import org.opencms.main.CmsEvent;
031import org.opencms.main.CmsLog;
032import org.opencms.main.I_CmsEventListener;
033import org.opencms.main.OpenCms;
034import org.opencms.monitor.CmsMemoryMonitor;
035
036import org.apache.commons.logging.Log;
037
038/**
039 * A singleton memory cache, that stores objects related with keys.<p>
040 *
041 * This cache listens to the {@link I_CmsEventListener#EVENT_CLEAR_CACHES} event only.<p>
042 *
043 * @since 6.2.3
044 */
045public final class CmsMemoryObjectCache implements I_CmsEventListener {
046
047    /** The log object for this class. */
048    private static final Log LOG = CmsLog.getLog(CmsMemoryObjectCache.class);
049
050    /** A cache that maps VFS resource names to Objects. */
051    private static CmsMemoryObjectCache m_instance;
052
053    /**
054     * Constructor, creates a new CmsVfsMemoryObjectCache.<p>
055     */
056    private CmsMemoryObjectCache() {
057
058        // register the event listeners
059        registerEventListener();
060    }
061
062    /**
063     * Returns the singleton memory Object cache instance.<p>
064     *
065     * @return the singleton memory Object cache instance
066     */
067    public static CmsMemoryObjectCache getInstance() {
068
069        if (m_instance == null) {
070            m_instance = new CmsMemoryObjectCache();
071        }
072        return m_instance;
073    }
074
075    /**
076     * @see org.opencms.main.I_CmsEventListener#cmsEvent(org.opencms.main.CmsEvent)
077     */
078    public void cmsEvent(CmsEvent event) {
079
080        switch (event.getType()) {
081            case I_CmsEventListener.EVENT_CLEAR_CACHES:
082                // flush cache
083                OpenCms.getMemoryMonitor().flushCache(CmsMemoryMonitor.CacheType.MEMORY_OBJECT);
084                if (LOG.isDebugEnabled()) {
085                    LOG.debug(
086                        org.opencms.xml.Messages.get().getBundle().key(
087                            org.opencms.xml.Messages.LOG_ERR_FLUSHED_CACHES_0));
088                }
089                break;
090            default:
091                // no operation
092        }
093    }
094
095    /**
096     * Returns an object from the cache.<p>
097     *
098     * @param owner the owner class of the cached object (used to ensure keys don't overlap)
099     * @param key the key to lookup the object for
100     *
101     * @return an object from the cache, or <code>null</code> if no object matches the given key
102     */
103    public Object getCachedObject(Class<?> owner, String key) {
104
105        key = owner.getName().concat(key);
106        return OpenCms.getMemoryMonitor().getCachedMemObject(key);
107    }
108
109    /**
110     * Puts an object into the cache.<p>
111     *
112     * @param owner the owner class of the cached object (used to ensure keys don't overlap)
113     * @param key the key to store the object at
114     * @param value the object to store
115     */
116    public void putCachedObject(Class<?> owner, String key, Object value) {
117
118        key = owner.getName().concat(key);
119        OpenCms.getMemoryMonitor().cacheMemObject(key, value);
120    }
121
122    /**
123     * Registers all required event listeners.<p>
124     */
125    protected void registerEventListener() {
126
127        // register this object as event listener
128        OpenCms.addCmsEventListener(this, new int[] {I_CmsEventListener.EVENT_CLEAR_CACHES});
129    }
130}