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？
private File file;
    public AbstractRegistry(URL url) {
        setUrl(url);
        
        syncSaveFile = url.getParameter(REGISTRY_FILESAVE_SYNC_KEY, false);
        String defaultFilename = System.getProperty("user.home") + "/.dubbo/dubbo-registry-" + url.getParameter(APPLICATION_KEY) + "-" + url.getAddress().replaceAll(":", "-") + ".cache";
        String filename = url.getParameter(FILE_KEY, defaultFilename);
        File file = null;
        if (ConfigUtils.isNotEmpty(filename)) {
            file = new File(filename);
            if (!file.exists() && file.getParentFile() != null && !file.getParentFile().exists()) {
                if (!file.getParentFile().mkdirs()) {
                    throw new IllegalArgumentException("Invalid registry cache file " + file + ", cause: Failed to create directory " + file.getParentFile() + "!");
                }
            }
        }
        this.file = file;
        
        
        loadProperties();
        notify(url.getBackupUrls());
    }
    protected static List<URL> filterEmpty(URL url, List<URL> urls) {
        if (CollectionUtils.isEmpty(urls)) {
            List<URL> result = new ArrayList<>(1);
            result.add(url.setProtocol(EMPTY_PROTOCOL));
            return result;
        }
        return urls;
    }