spring中的组合模式

org.springframework.cache.support.CompositeCacheManager
/*

 * Copyright 2002-2016 the original author or authors.

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *      https://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package org.springframework.cache.support;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.Collection;

import java.util.Collections;

import java.util.LinkedHashSet;

import java.util.List;

import java.util.Set;

import org.springframework.beans.factory.InitializingBean;

import org.springframework.cache.Cache;

import org.springframework.cache.CacheManager;

import org.springframework.lang.Nullable;

/**

 * Composite {@link CacheManager} implementation that iterates over

 * a given collection of delegate {@link CacheManager} instances.

 *

 * <p>Allows {@link NoOpCacheManager} to be automatically added to the end of

 * the list for handling cache declarations without a backing store. Otherwise,

 * any custom {@link CacheManager} may play that role of the last delegate as

 * well, lazily creating cache regions for any requested name.

 *

 * <p>Note: Regular CacheManagers that this composite manager delegates to need

 * to return {@code null} from {@link #getCache(String)} if they are unaware of

 * the specified cache name, allowing for iteration to the next delegate in line.

 * However, most {@link CacheManager} implementations fall back to lazy creation

 * of named caches once requested; check out the specific configuration details

 * for a 'static' mode with fixed cache names, if available.

 *

 * @author Costin Leau

 * @author Juergen Hoeller

 * @since 3.1

 * @see #setFallbackToNoOpCache

 * @see org.springframework.cache.concurrent.ConcurrentMapCacheManager#setCacheNames

 */

public class CompositeCacheManager implements CacheManager, InitializingBean {

	private final List<CacheManager> cacheManagers = new ArrayList<>();

	private boolean fallbackToNoOpCache = false;

	/**

	 * Construct an empty CompositeCacheManager, with delegate CacheManagers to

	 * be added via the {@link #setCacheManagers "cacheManagers"} property.

	 */

	public CompositeCacheManager() {

	}

	/**

	 * Construct a CompositeCacheManager from the given delegate CacheManagers.

	 * @param cacheManagers the CacheManagers to delegate to

	 */

	public CompositeCacheManager(CacheManager... cacheManagers) {

		setCacheManagers(Arrays.asList(cacheManagers));

	}

	/**

	 * Specify the CacheManagers to delegate to.

	 */

	public void setCacheManagers(Collection<CacheManager> cacheManagers) {

		this.cacheManagers.addAll(cacheManagers);

	}

	/**

	 * Indicate whether a {@link NoOpCacheManager} should be added at the end of the delegate list.

	 * In this case, any {@code getCache} requests not handled by the configured CacheManagers will

	 * be automatically handled by the {@link NoOpCacheManager} (and hence never return {@code null}).

	 */

	public void setFallbackToNoOpCache(boolean fallbackToNoOpCache) {

		this.fallbackToNoOpCache = fallbackToNoOpCache;

	}

	@Override

	public void afterPropertiesSet() {

		if (this.fallbackToNoOpCache) {

			this.cacheManagers.add(new NoOpCacheManager());

		}

	}

	@Override

	@Nullable

	public Cache getCache(String name) {

		for (CacheManager cacheManager : this.cacheManagers) {

			Cache cache = cacheManager.getCache(name);

			if (cache != null) {

				return cache;

			}

		}

		return null;

	}

	@Override

	public Collection<String> getCacheNames() {

		Set<String> names = new LinkedHashSet<>();

		for (CacheManager manager : this.cacheManagers) {

			names.addAll(manager.getCacheNames());

		}

		return Collections.unmodifiableSet(names);

	}

}
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spring中的组合模式

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