if (url != null && url.length() > 0) { // user specified URL, could be peer-to-peer address, or register center's address.
    String[] us = Constants.SEMICOLON_SPLIT_PATTERN.split(url);
    if (us != null && us.length > 0) {
        for (String u : us) {
            URL url = URL.valueOf(u);
            if (url.getPath() == null || url.getPath().length() == 0) {
                url = url.setPath(interfaceName);
            }
            if (Constants.REGISTRY_PROTOCOL.equals(url.getProtocol())) {
                urls.add(url.addParameterAndEncoded(Constants.REFER_KEY, StringUtils.toQueryString(map)));
            } else {
                urls.add(ClusterUtils.mergeUrl(url, map));
            }
        }
    }
} else { // assemble URL from register center's configuration

    <dubbo:consumer>
        <dubbo:parameter key="serialization" value="kryo" />
    </dubbo:consumer>