sample code to use memcached in google app engine.

CacheUtil.java

package util;

import java.util.Collections;
import java.util.logging.Logger;

import javax.cache.Cache;
import javax.cache.CacheException;
import javax.cache.CacheFactory;
import javax.cache.CacheManager;

import com.google.appengine.api.memcache.InvalidValueException;
import com.google.appengine.api.memcache.stdimpl.GCacheException;

public class CacheUtil {

	static final Logger log = Logger.getLogger(CacheUtil.class.getName());

	private CacheUtil(){
	}

	private static Cache getCache() {
		Cache cache = null;
		try {
			CacheFactory cacheFactory = CacheManager.getInstance().getCacheFactory();
			cache = cacheFactory.createCache(Collections.emptyMap());
		} catch (CacheException e) {
			log.warning(e.getClass().getSimpleName() + ": " + e.getMessage());
			return null;
		}

		return cache;
	}

	public static <T> boolean isCached(String key, T type){
		Cache cache = getCache();
		if(cache == null){
			log.warning("cache is null.");
			return false;
		}

		if(!cache.containsKey(key)){
			log.warning("containsKey()がfalse");
			return false;
		}

		Object object = cache.get(key);
		if(object == null){
			log.warning("object is null.");
			return false;
		}
		if(!object.getClass().getSimpleName().equals(type.getClass().getSimpleName())) {
			log.warning("getSimpleName()が一致していない");
			return false;
		}

		return true;
	}

	/**
	 *
	 * @param key
	 * @param value
	 * @return
	 */
	@SuppressWarnings("unchecked")
	public static boolean put(String key, Object value){
		boolean isPutted = true;
//		long start = 0, end = 0;
//		start = System.currentTimeMillis();

		try {
			getCache().put(key, value);
		} catch (GCacheException e) {
			log.warning(e.getClass().getSimpleName() + ": " + key + "," + value + ", " + e.getMessage());
			isPutted = false;
		}
//		end = System.currentTimeMillis();
//
//		if(isPutted)
//			log.info(value.getClass().getSimpleName() + " is putted: " + (double)(end - start)/1000 + "秒, " + key + ", " + value);
//		else
//			log.info(value.getClass().getSimpleName() + " is NOT putted: " + (double)(end - start)/1000 + "秒, " + key + ", " + value);

		return isPutted;
	}

	/**
	 *
	 * @param <T>
	 * @param key
	 * @param type 取り出すオブジェクトの型。これが一致しないとエクセプションが起きる
	 * @param init trueにしておくと、typeと違うオブジェクトが格納されていた場合に、値を初期化する
	 * @return
	 */
	@SuppressWarnings("unchecked")
	public static <T> T get(String key, T type, boolean init){
//		long start = 0, end = 0;
//		start = System.currentTimeMillis();

		if(init){
			if(!isCached(key, type)){
				put(key, type);
				log.warning("initialized, key=" + key + ", type=" + type.getClass().getSimpleName() + ", object=" + getCache().get(key).getClass().getSimpleName());
			}
		}
		T dataToReturn = null;
		try {
			dataToReturn = (T) getCache().get(key);
		} catch (InvalidValueException e) {
			log.warning(e.getClass().getSimpleName() + ": " + key + ", " + e.getMessage());
			return null;
		}
		// ClassCastExceptionはこのメソッドの呼び出し元で起こる
//		end = System.currentTimeMillis();
//		log.info(key + ", " +  (double) (end - start)/1000 + "秒");

		return  dataToReturn;
	}

	/**
	 * 明示的に削除しなくても容量が圧迫されると自動的に削除される
	 * @param key
	 */
	public static void remove(String key){
		getCache().remove(key);
	}

	public static void removeAll(){
		getCache().clear();
	}

	public static int size(){
		return getCache().size();
	}

	public static int getCacheHits(){
		return getCache().getCacheStatistics().getCacheHits();
	}

	public static int getCacheMisses(){
		return getCache().getCacheStatistics().getCacheMisses();
	}

}

Thanks for this file...
How can authorize my application with *.p12 file for memcache ?