001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one
003     * or more contributor license agreements.  See the NOTICE file
004     * distributed with this work for additional information
005     * regarding copyright ownership.  The ASF licenses this file
006     * to you under the Apache License, Version 2.0 (the
007     * "License"); you may not use this file except in compliance
008     * with the License.  You may obtain a copy of the License at
009     *
010     *     http://www.apache.org/licenses/LICENSE-2.0
011     *
012     * Unless required by applicable law or agreed to in writing,
013     * software distributed under the License is distributed on an
014     * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015     * KIND, either express or implied.  See the License for the
016     * specific language governing permissions and limitations
017     * under the License.
018     */
019    package org.apache.shiro.session.mgt.eis;
020    
021    import org.apache.shiro.session.Session;
022    import org.apache.shiro.session.UnknownSessionException;
023    import org.apache.shiro.util.CollectionUtils;
024    import org.slf4j.Logger;
025    import org.slf4j.LoggerFactory;
026    
027    import java.io.Serializable;
028    import java.util.Collection;
029    import java.util.Collections;
030    import java.util.concurrent.ConcurrentHashMap;
031    import java.util.concurrent.ConcurrentMap;
032    
033    
034    /**
035     * Simple memory-based implementation of the SessionDAO that stores all of its sessions in an in-memory
036     * {@link ConcurrentMap}.  <b>This implementation does not page to disk and is therefore unsuitable for applications
037     * that could experience a large amount of sessions</b> and would therefore cause {@code OutOfMemoryException}s.  It is
038     * <em>not</em> recommended for production use in most environments.
039     * <h2>Memory Restrictions</h2>
040     * If your application is expected to host many sessions beyond what can be stored in the
041     * memory available to the JVM, it is highly recommended to use a different {@code SessionDAO} implementation which
042     * uses a more expansive or permanent backing data store.
043     * <p/>
044     * In this case, it is recommended to instead use a custom
045     * {@link CachingSessionDAO} implementation that communicates with a higher-capacity data store of your choice
046     * (file system, database, etc).
047     * <h2>Changes in 1.0</h2>
048     * This implementation prior to 1.0 used to subclass the {@link CachingSessionDAO}, but this caused problems with many
049     * cache implementations that would expunge entries due to TTL settings, resulting in Sessions that would be randomly
050     * (and permanently) lost.  The Shiro 1.0 release refactored this implementation to be 100% memory-based (without
051     * {@code Cache} usage to avoid this problem.
052     *
053     * @see CachingSessionDAO
054     * @since 0.1
055     */
056    public class MemorySessionDAO extends AbstractSessionDAO {
057    
058        private static final Logger log = LoggerFactory.getLogger(MemorySessionDAO.class);
059    
060        private ConcurrentMap<Serializable, Session> sessions;
061    
062        public MemorySessionDAO() {
063            this.sessions = new ConcurrentHashMap<Serializable, Session>();
064        }
065    
066        protected Serializable doCreate(Session session) {
067            Serializable sessionId = generateSessionId(session);
068            assignSessionId(session, sessionId);
069            storeSession(sessionId, session);
070            return sessionId;
071        }
072    
073        protected Session storeSession(Serializable id, Session session) {
074            if (id == null) {
075                throw new NullPointerException("id argument cannot be null.");
076            }
077            return sessions.putIfAbsent(id, session);
078        }
079    
080        protected Session doReadSession(Serializable sessionId) {
081            return sessions.get(sessionId);
082        }
083    
084        public void update(Session session) throws UnknownSessionException {
085            storeSession(session.getId(), session);
086        }
087    
088        public void delete(Session session) {
089            if (session == null) {
090                throw new NullPointerException("session argument cannot be null.");
091            }
092            Serializable id = session.getId();
093            if (id != null) {
094                sessions.remove(id);
095            }
096        }
097    
098        public Collection<Session> getActiveSessions() {
099            Collection<Session> values = sessions.values();
100            if (CollectionUtils.isEmpty(values)) {
101                return Collections.emptySet();
102            } else {
103                return Collections.unmodifiableCollection(values);
104            }
105        }
106    
107    }