Java Memcached不返回存储的bytearray

Amazon Elasticache用作Memcached来存储输入流（转换为字节数组），如下所示

除了第一次启动应用程序外，返回的字节数组始终为“null”

我的问题

为什么Memcached会返回一个空字节数组（第一次除外）

如何检查字节数组是否成功写入Memcached

private static final int MEMCACHED_TIME_TO_LIVE = 15 * 60;
InputStream stream = item.openStream();

byte[] byteArray = IOUtils.toByteArray(stream);


MemcachedClient memcachedClient = new MemcachedClient(new InetSocketAddress(AMAZON_ELASTICACHE_CLUSTER_ENDPOINT,AMAZON_ELASTICACHE_CLUSTER_PORT));
String key = name;

Future<Boolean> result = memcachedClient.set(key, MEMCACHED_TIME_TO_LIVE,byteArray);

memcachedClient.shutdown();

MemcachedClient memcachedClient = new MemcachedClient(new InetSocketAddress(AMAZON_ELASTICACHE_CLUSTER_ENDPOINT,
                    AMAZON_ELASTICACHE_CLUSTER_PORT));

String key = name;
byte[] byteArray = (byte[]) memcachedClient.get(key);
memcachedClient.shutdown();