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.file.CmsObject;
031import org.opencms.file.CmsResource;
032import org.opencms.main.CmsLog;
033import org.opencms.main.OpenCms;
034import org.opencms.monitor.CmsMemoryMonitor;
035
036import org.apache.commons.collections.Transformer;
037import org.apache.commons.logging.Log;
038
039/**
040 * Implements a memory cache, that stores objects related to VFS files,
041 * providing a cache for the "online" and another for the "offline" project.<p>
042 *
043 * @since 6.1.3
044 */
045public class CmsVfsMemoryObjectCache extends CmsVfsCache {
046
047    /** Counts the number of instances created. */
048    private static int instanceCounter;
049
050    /** The log object for this class. */
051    private static final Log LOG = CmsLog.getLog(CmsVfsMemoryObjectCache.class);
052
053    /** A cache that maps VFS resource names to Objects. */
054    private static CmsVfsMemoryObjectCache m_vfsMemoryObjectCache;
055
056    /** The id for this instance, which is used for distinguishing cache keys of different instances. */
057    private int m_id;
058
059    /**
060     * Constructor, creates a new CmsVfsMemoryObjectCache.<p>
061     */
062    public CmsVfsMemoryObjectCache() {
063
064        m_id = instanceCounter;
065        instanceCounter += 1;
066        // register the event listeners
067        registerEventListener();
068    }
069
070    /**
071     * Returns the VFS memory Object cache.<p>
072     *
073     * @return the VFS memory Object cache
074     */
075    public static CmsVfsMemoryObjectCache getVfsMemoryObjectCache() {
076
077        if (m_vfsMemoryObjectCache == null) {
078            m_vfsMemoryObjectCache = new CmsVfsMemoryObjectCache();
079        }
080        return m_vfsMemoryObjectCache;
081    }
082
083    /**
084     * Return an object from the cache.<p>
085     *
086     * @param cms the current users OpenCms context
087     * @param rootPath the rootPath of the VFS resource to get the object for
088     * @return object form cache or null
089     */
090    public Object getCachedObject(CmsObject cms, String rootPath) {
091
092        String key = getCacheKeyForCurrentProject(cms, rootPath);
093        return OpenCms.getMemoryMonitor().getCachedVfsObject(key);
094    }
095
096    /**
097     * Uses a transformer for loading an object from a path if it has not already been cached, and then caches it.<p>
098     *
099     * @param cms the CMS context
100     * @param rootPath the root path from which the object should be loaded
101     * @param function the function which should load the object from VFS if it isn't already cached
102     *
103     * @return the loaded object
104     */
105    public Object loadVfsObject(CmsObject cms, String rootPath, Transformer function) {
106
107        Object result = getCachedObject(cms, rootPath);
108        if (result == null) {
109            result = function.transform(rootPath);
110            putCachedObject(cms, rootPath, result);
111        }
112        return result;
113    }
114
115    /**
116     * Puts an object into the cache.<p>
117     *
118     * @param cms the CmsObject
119     * @param rootPath the rootPath of the VFS resource to store the object for
120     * @param value the object to store
121     */
122    public void putCachedObject(CmsObject cms, String rootPath, Object value) {
123
124        String key = getCacheKeyForCurrentProject(cms, rootPath);
125        OpenCms.getMemoryMonitor().cacheVfsObject(key, value);
126    }
127
128    /**
129     * @see org.opencms.cache.CmsVfsCache#flush(boolean)
130     */
131    @Override
132    protected void flush(boolean online) {
133
134        OpenCms.getMemoryMonitor().flushCache(CmsMemoryMonitor.CacheType.VFS_OBJECT);
135    }
136
137    /**
138     * @see org.opencms.cache.CmsVfsCache#uncacheResource(org.opencms.file.CmsResource)
139     */
140    @Override
141    protected void uncacheResource(CmsResource resource) {
142
143        uncacheSystemId(resource.getRootPath());
144    }
145
146    /**
147     * Returns a cache key for the given system id (filename) based on the status
148     * of the given project flag.<p>
149     *
150     * @param systemId the system id (filename) to get the cache key for
151     * @param online indicates if this key is generated for the online project
152     *
153     * @return the cache key for the system id
154     */
155    private String getCacheKey(String systemId, boolean online) {
156
157        if (online) {
158            return "online_(" + m_id + ")_" + systemId;
159        }
160        return "offline_(" + m_id + ")_" + systemId;
161    }
162
163    /**
164     * Returns a cache key for the given root path based on the status
165     * of the given CmsObject.<p>
166     *
167     * @param cms the cms context
168     * @param rootPath the filename to get the cache key for
169     *
170     * @return the cache key for the system id
171     */
172    private String getCacheKeyForCurrentProject(CmsObject cms, String rootPath) {
173
174        // check the project
175        boolean project = (cms != null) ? cms.getRequestContext().getCurrentProject().isOnlineProject() : false;
176        return getCacheKey(rootPath, project);
177    }
178
179    /**
180     * Uncaches a system id (filename) from the internal offline temporary and content definitions caches.<p>
181     *
182     * The online resources cached for the online project are only flushed when a project is published.<p>
183     *
184     * @param systemId the system id (filename) to uncache
185     */
186    private void uncacheSystemId(String systemId) {
187
188        String key = getCacheKey(systemId, false);
189        Object o = OpenCms.getMemoryMonitor().getCachedVfsObject(key);
190        OpenCms.getMemoryMonitor().uncacheVfsObject(key);
191        if ((null != o) && LOG.isDebugEnabled()) {
192            LOG.debug(
193                org.opencms.xml.Messages.get().getBundle().key(
194                    org.opencms.xml.Messages.LOG_ERR_UNCACHED_SYS_ID_1,
195                    key));
196        }
197    }
198}