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Java client for Arcus memcached
There is a newer version: 1.13.2
/*
 * arcus-java-client : Arcus Java client
 * Copyright 2010-2014 NAVER Corp.
 *
 * 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
 *
 * http://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 net.spy.memcached.plugin;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.util.List;
import java.util.concurrent.Future;

import net.sf.ehcache.Element;
import net.spy.memcached.ConnectionFactory;
import net.spy.memcached.MemcachedClient;
import net.spy.memcached.transcoders.Transcoder;

/**
 * Front cache for some Arcus commands.
 * For now, it supports get commands.  The front cache stores the value from a get operation.
 * A subsequent get operation first checks the cache.  If the key is found in the cache,
 * it is returned from the front cache.  If not, the get command goes to the server as usual.
 *
 * Cache parameters (name, size, expiration time) are from ConnectionFactory.
 * @see net.spy.memcached.ConnectionFactoryBuilder
 * @see net.spy.memcached.plugin.LocalCacheManager
 */
public class FrontCacheMemcachedClient extends MemcachedClient {

	/**
	 * Create the memcached client and the front cache.
	 *
	 * @param cf  the connection factory to configure connections for this client
	 * @param addrs  the socket addresses for the memcached servers
	 * @throws IOException if connections cannot be established
	 */
	public FrontCacheMemcachedClient(ConnectionFactory cf,
			List addrs) throws IOException {
		super(cf, addrs);

		if (cf.getMaxFrontCacheElements() > 0) {
			String cacheName = cf.getFrontCacheName();
			int maxElements = cf.getMaxFrontCacheElements();
			int timeToLiveSeconds = cf.getFrontCacheExpireTime();
			boolean copyOnRead = cf.getFrontCacheCopyOnRead();
			boolean copyOnWrite = cf.getFrontCacheCopyOnWrite();
			// TODO add an additional option
			// int timeToIdleSeconds = timeToLiveSeconds;
			
			localCacheManager = new LocalCacheManager(cacheName, maxElements,
					timeToLiveSeconds, copyOnRead, copyOnWrite);
		}
	}

	/**
	 * Get the value of the key.
         * Check the local cache first. If the key is not found, send the command to the server.
	 *
	 * @param key  the key to fetch
	 * @param tc  the transcoder to serialize and unserialize value
	 * @return a future that will hold the value of the key
	 */
	@Override
	public  Future asyncGet(final String key, final Transcoder tc) {
		Element frontElement = null;

		if (localCacheManager != null) {
			frontElement = localCacheManager.getElement(key);
		}

		if (frontElement == null) {
			return super.asyncGet(key, tc);
		} else {
			return new FrontCacheGetFuture(frontElement);
		}
	}

	/**
	 * Delete the key.
         * Delete the key from the local cache before sending the command to the server.
	 *
	 * @param key  the key to delete
	 * @return a future that will hold success/error status of the operation
	 */
	@Override
	public Future delete(String key) {
		if (localCacheManager != null) {
			localCacheManager.delete(key);
		}
		return super.delete(key);
	}

}