你好：
我有一个疑问，当Registry调用destroy后不会去清除AbstractRegistryFactory中的缓存，导致以同样的参数再次获取的时候得到了一个已经无法使用的Registry。这个时设计的时候就认为不该这么使用吗？
import static org.apache.dubbo.common.constants.RegistryConstants.CATEGORY_KEY;
import static org.apache.dubbo.common.constants.RegistryConstants.DEFAULT_CATEGORY;
import static org.apache.dubbo.common.constants.RegistryConstants.DYNAMIC_KEY;
import static org.apache.dubbo.common.constants.RegistryConstants.EMPTY_PROTOCOL;
import static org.apache.dubbo.registry.Constants.REGISTRY_FILESAVE_SYNC_KEY;
/**
 * AbstractRegistry. (SPI, Prototype, ThreadSafe)
 */
public abstract class AbstractRegistry implements Registry {
    
    private static final char URL_SEPARATOR = ' ';
    
    private static final String URL_SPLIT = "\\s+";
    
    private static final int MAX_RETRY_TIMES_SAVE_PROPERTIES = 3;
    
    protected final Logger logger = LoggerFactory.getLogger(getClass());
    
    private final Properties properties = new Properties();
    
    private final ExecutorService registryCacheExecutor = Executors.newFixedThreadPool(1, new NamedThreadFactory("DubboSaveRegistryCache", true));
    
    private final boolean syncSaveFile;
    private final AtomicLong lastCacheChanged = new AtomicLong();
    private final AtomicInteger savePropertiesRetryTimes = new AtomicInteger();
    private final Set<URL> registered = new ConcurrentHashSet<>();
    private final ConcurrentMap<URL, Set<NotifyListener>> subscribed = new ConcurrentHashMap<>();
    private final ConcurrentMap<URL, Map<String, List<URL>>> notified = new ConcurrentHashMap<>();
    private URL registryUrl;