001/*
002 * Copyright 2002-2014 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.cache.support;
018
019import java.util.ArrayList;
020import java.util.Arrays;
021import java.util.Collection;
022import java.util.Collections;
023import java.util.LinkedHashSet;
024import java.util.List;
025import java.util.Set;
026
027import org.springframework.beans.factory.InitializingBean;
028import org.springframework.cache.Cache;
029import org.springframework.cache.CacheManager;
030
031/**
032 * Composite {@link CacheManager} implementation that iterates over
033 * a given collection of delegate {@link CacheManager} instances.
034 *
035 * <p>Allows {@link NoOpCacheManager} to be automatically added to the end of
036 * the list for handling cache declarations without a backing store. Otherwise,
037 * any custom {@link CacheManager} may play that role of the last delegate as
038 * well, lazily creating cache regions for any requested name.
039 *
040 * <p>Note: Regular CacheManagers that this composite manager delegates to need
041 * to return {@code null} from {@link #getCache(String)} if they are unaware of
042 * the specified cache name, allowing for iteration to the next delegate in line.
043 * However, most {@link CacheManager} implementations fall back to lazy creation
044 * of named caches once requested; check out the specific configuration details
045 * for a 'static' mode with fixed cache names, if available.
046 *
047 * @author Costin Leau
048 * @author Juergen Hoeller
049 * @since 3.1
050 * @see #setFallbackToNoOpCache
051 * @see org.springframework.cache.concurrent.ConcurrentMapCacheManager#setCacheNames
052 */
053public class CompositeCacheManager implements CacheManager, InitializingBean {
054
055        private final List<CacheManager> cacheManagers = new ArrayList<CacheManager>();
056
057        private boolean fallbackToNoOpCache = false;
058
059
060        /**
061         * Construct an empty CompositeCacheManager, with delegate CacheManagers to
062         * be added via the {@link #setCacheManagers "cacheManagers"} property.
063         */
064        public CompositeCacheManager() {
065        }
066
067        /**
068         * Construct a CompositeCacheManager from the given delegate CacheManagers.
069         * @param cacheManagers the CacheManagers to delegate to
070         */
071        public CompositeCacheManager(CacheManager... cacheManagers) {
072                setCacheManagers(Arrays.asList(cacheManagers));
073        }
074
075
076        /**
077         * Specify the CacheManagers to delegate to.
078         */
079        public void setCacheManagers(Collection<CacheManager> cacheManagers) {
080                this.cacheManagers.addAll(cacheManagers);
081        }
082
083        /**
084         * Indicate whether a {@link NoOpCacheManager} should be added at the end of the delegate list.
085         * In this case, any {@code getCache} requests not handled by the configured CacheManagers will
086         * be automatically handled by the {@link NoOpCacheManager} (and hence never return {@code null}).
087         */
088        public void setFallbackToNoOpCache(boolean fallbackToNoOpCache) {
089                this.fallbackToNoOpCache = fallbackToNoOpCache;
090        }
091
092        @Override
093        public void afterPropertiesSet() {
094                if (this.fallbackToNoOpCache) {
095                        this.cacheManagers.add(new NoOpCacheManager());
096                }
097        }
098
099
100        @Override
101        public Cache getCache(String name) {
102                for (CacheManager cacheManager : this.cacheManagers) {
103                        Cache cache = cacheManager.getCache(name);
104                        if (cache != null) {
105                                return cache;
106                        }
107                }
108                return null;
109        }
110
111        @Override
112        public Collection<String> getCacheNames() {
113                Set<String> names = new LinkedHashSet<String>();
114                for (CacheManager manager : this.cacheManagers) {
115                        names.addAll(manager.getCacheNames());
116                }
117                return Collections.unmodifiableSet(names);
118        }
119
120}