Eu tento acessar uma lista do Sharepoint via JAX-WS, conforme descritoaqui

No entanto, ao executar o código abaixo, recebo:

java.lang.Exception: Exception. See stacktrace.com.sun.xml.internal.ws.client.ClientTransportException: The server sent HTTP status code 401: Unauthorized

O Sharepoint requer autenticação NTLM. O que pode ser o problema? Muito obrigado!

public static ListsSoap sharePointListsAuth(String userName, String password) throws Exception {
    ListsSoap port = null;
    if (userName != null && password != null) {
        try {
            Lists service = new Lists();
            port = service.getListsSoap();
            System.out.println("Web Service Auth Username: " + userName);
            ((BindingProvider) port).getRequestContext().put(BindingProvider.USERNAME_PROPERTY, userName);
            ((BindingProvider) port).getRequestContext().put(BindingProvider.PASSWORD_PROPERTY, password);
        } catch (Exception e) {
            throw new Exception("Error: " + e.toString());
        }
    } else {
        throw new Exception("Couldn't authenticate: Invalid connection details given.");
    }
    return port;
}