private URL getResourceForOptionalProperty(final IClientConfigKey configKey) {
        final String propValue = (String) ncc.get(configKey);
        URL result = null;

        if (propValue != null) {
            result = getResource(propValue);
            if (result == null) {
                throw new IllegalArgumentException("No resource found for " + configKey + ": "
                        + propValue);
            }
        }
        return result;
    }
A client that is essentially a wrapper around Jersey client. By default, it uses HttpClient for underlying HTTP communication.
Application can set its own Jersey client with this class, but doing so will void all client configurations set in {@link IClientConfig}.

@deprecated Please see ribbon-rxnetty module for the Netty based client. 

@author awang
ribbon-httpclient/src/main/java/com/netflix/niws/client/http/RestClient.java