web services - Java password protected webservice trough proxy server -

i'm trying call pasword protected web service. when use server's ip address, works fine:

public class mywsclient extends cxfclientbase<myws>  {   public mywsclient ()    {   super(         "https://xxx.xxx.xxx.xxx:yyyy/somewebservice",      ...      );       bindingprovider prov = (bindingprovider)port;      prov.getrequestcontext().put(bindingprovider.username_property, "username");      prov.getrequestcontext().put(bindingprovider.password_property, "password");      ...   } 

but need proxy server, if want use server's dns name. so, added following code:

system.setproperty("https.proxyhost", "xxx.xxx.xxx.xxx"); system.setproperty("https.proxyport", "8080"); 

it relays dns name, 401 authentication error web service.

why doesn't work authentication, when use proxy server?