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.cache;
020    
021    import org.apache.shiro.util.Destroyable;
022    import org.apache.shiro.util.LifecycleUtils;
023    import org.apache.shiro.util.StringUtils;
024    
025    import java.util.Collection;
026    import java.util.concurrent.ConcurrentHashMap;
027    import java.util.concurrent.ConcurrentMap;
028    
029    /**
030     * Very simple abstract {@code CacheManager} implementation that retains all created {@link Cache Cache} instances in
031     * an in-memory {@link ConcurrentMap ConcurrentMap}.  {@code Cache} instance creation is left to subclasses via
032     * the {@link #createCache createCache} method implementation.
033     *
034     * @since 1.0
035     */
036    public abstract class AbstractCacheManager implements CacheManager, Destroyable {
037    
038        /**
039         * Retains all Cache objects maintained by this cache manager.
040         */
041        private final ConcurrentMap<String, Cache> caches;
042    
043        /**
044         * Default no-arg constructor that instantiates an internal name-to-cache {@code ConcurrentMap}.
045         */
046        public AbstractCacheManager() {
047            this.caches = new ConcurrentHashMap<String, Cache>();
048        }
049    
050        /**
051         * Returns the cache with the specified {@code name}.  If the cache instance does not yet exist, it will be lazily
052         * created, retained for further access, and then returned.
053         *
054         * @param name the name of the cache to acquire.
055         * @return the cache with the specified {@code name}.
056         * @throws IllegalArgumentException if the {@code name} argument is {@code null} or does not contain text.
057         * @throws CacheException           if there is a problem lazily creating a {@code Cache} instance.
058         */
059        public <K, V> Cache<K, V> getCache(String name) throws IllegalArgumentException, CacheException {
060            if (!StringUtils.hasText(name)) {
061                throw new IllegalArgumentException("Cache name cannot be null or empty.");
062            }
063    
064            Cache cache;
065    
066            cache = caches.get(name);
067            if (cache == null) {
068                cache = createCache(name);
069                Cache existing = caches.putIfAbsent(name, cache);
070                if (existing != null) {
071                    cache = existing;
072                }
073            }
074    
075            //noinspection unchecked
076            return cache;
077        }
078    
079        /**
080         * Creates a new {@code Cache} instance associated with the specified {@code name}.
081         *
082         * @param name the name of the cache to create
083         * @return a new {@code Cache} instance associated with the specified {@code name}.
084         * @throws CacheException if the {@code Cache} instance cannot be created.
085         */
086        protected abstract Cache createCache(String name) throws CacheException;
087    
088        /**
089         * Cleanup method that first {@link LifecycleUtils#destroy destroys} all of it's managed caches and then
090         * {@link java.util.Map#clear clears} out the internally referenced cache map.
091         *
092         * @throws Exception if any of the managed caches can't destroy properly.
093         */
094        public void destroy() throws Exception {
095            while (!caches.isEmpty()) {
096                for (Cache cache : caches.values()) {
097                    LifecycleUtils.destroy(cache);
098                }
099                caches.clear();
100            }
101        }
102    
103        public String toString() {
104            Collection<Cache> values = caches.values();
105            StringBuilder sb = new StringBuilder(getClass().getSimpleName())
106                    .append(" with ")
107                    .append(caches.size())
108                    .append(" cache(s)): [");
109            int i = 0;
110            for (Cache cache : values) {
111                if (i > 0) {
112                    sb.append(", ");
113                }
114                sb.append(cache.toString());
115                i++;
116            }
117            sb.append("]");
118            return sb.toString();
119        }
120    }