Estou tentando instanciar um cliente de serviço da Web em Java, cujo URL é protegido por nome de usuário e senha. Ao instanciar, lança uma WebServiceException; aqui está o stacktrace:

javax.xml.ws.WebServiceException: java.io.FileNotFoundException: Response: '401: Unauthorized' for url: WSDLURL
at com.sun.xml.ws.wsdl.WSDLContext.<init>(WSDLContext.java:68)
at com.sun.xml.ws.client.WSServiceDelegate.parseWSDL(WSServiceDelegate.java:207)
at com.sun.xml.ws.client.WSServiceDelegate.<init>(WSServiceDelegate.java:165)
at com.sun.xml.ws.spi.ProviderImpl.createServiceDelegate(ProviderImpl.java:49)
at weblogic.wsee.jaxws.spi.WLSProvider.createServiceDelegate(WLSProvider.java:18)
at javax.xml.ws.Service.<init>(Service.java:57)
at org.openuri.ServiceUtilityWS.<init>(ServiceUtilityWS.java:36)
at it.cartasi.pb.giustificatomotivo.util.Util.sendEmail(Util.java:110)
at it.cartasi.pb.giustificatomotivo.action.ConfermaAction.execute(ConfermaAction.java:36)
at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:419)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:224)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
at weblogic.servlet.internal.StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:226)
at weblogic.servlet.internal.StubSecurityHelper.invokeServlet(StubSecurityHelper.java:124)
at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:283)
at weblogic.servlet.internal.TailFilter.doFilter(TailFilter.java:26)
at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:42)
at it.cartasi.pb.giustificatomotivo.filter.SessionFilter.doFilter(SessionFilter.java:68)
at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:42)
at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.run(WebAppServletContext.java:3402)
at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:321)
at weblogic.security.service.SecurityManager.runAs(Unknown Source)
at weblogic.servlet.internal.WebAppServletContext.securedExecute(WebAppServletContext.java:2140)
at weblogic.servlet.internal.WebAppServletContext.execute(WebAppServletContext.java:2046)
at weblogic.servlet.internal.ServletRequestImpl.run(ServletRequestImpl.java:1398)
at weblogic.work.ExecuteThread.execute(ExecuteThread.java:200)
at weblogic.work.ExecuteThread.run(ExecuteThread.java:172)
java.io.FileNotFoundException: Response: '401: Unauthorized' for url: WSDLURL
    at weblogic.net.http.HttpURLConnection.getInputStream(HttpURLConnection.java:467)
    at weblogic.net.http.SOAPHttpURLConnection.getInputStream(SOAPHttpURLConnection.java:36)
    at java.net.URL.openStream(URL.java:1007)
    at com.sun.xml.ws.wsdl.parser.RuntimeWSDLParser.createReader(RuntimeWSDLParser.java:666)
    at com.sun.xml.ws.wsdl.parser.RuntimeWSDLParser.parseWSDL(RuntimeWSDLParser.java:152)
    at com.sun.xml.ws.wsdl.parser.RuntimeWSDLParser.parse(RuntimeWSDLParser.java:99)
    at com.sun.xml.ws.wsdl.WSDLContext.<init>(WSDLContext.java:65)
    at com.sun.xml.ws.client.WSServiceDelegate.parseWSDL(WSServiceDelegate.java:207)
    at com.sun.xml.ws.client.WSServiceDelegate.<init>(WSServiceDelegate.java:165)
    at com.sun.xml.ws.spi.ProviderImpl.createServiceDelegate(ProviderImpl.java:49)
    at weblogic.wsee.jaxws.spi.WLSProvider.createServiceDelegate(WLSProvider.java:18)
    at javax.xml.ws.Service.<init>(Service.java:57)
    at org.openuri.ServiceUtilityWS.<init>(ServiceUtilityWS.java:36)
    at it.cartasi.pb.giustificatomotivo.util.Util.sendEmail(Util.java:110)
    at it.cartasi.pb.giustificatomotivo.action.ConfermaAction.execute(ConfermaAction.java:36)
    at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:419)
    at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:224)
    at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
    at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
    at weblogic.servlet.internal.StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:226)
    at weblogic.servlet.internal.StubSecurityHelper.invokeServlet(StubSecurityHelper.java:124)
    at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:283)
    at weblogic.servlet.internal.TailFilter.doFilter(TailFilter.java:26)
    at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:42)
    at it.cartasi.pb.giustificatomotivo.filter.SessionFilter.doFilter(SessionFilter.java:68)
    at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:42)
    at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.run(WebAppServletContext.java:3402)
    at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:321)
    at weblogic.security.service.SecurityManager.runAs(Unknown Source)
    at weblogic.servlet.internal.WebAppServletContext.securedExecute(WebAppServletContext.java:2140)
    at weblogic.servlet.internal.WebAppServletContext.execute(WebAppServletContext.java:2046)
    at weblogic.servlet.internal.ServletRequestImpl.run(ServletRequestImpl.java:1398)
    at weblogic.work.ExecuteThread.execute(ExecuteThread.java:200)
    at weblogic.work.ExecuteThread.run(ExecuteThread.java:172)

Aqui meu trecho de código (eu também defino o Autenticador padrão):

Authenticator.setDefault(new Authenticator() {
        @Override
        protected PasswordAuthentication getPasswordAuthentication() {
            char[] charArray = password.toCharArray();
            System.out.println(user);
            System.out.println(charArray);
            return new PasswordAuthentication(
                    user,
                    charArray);
        }
    });

    try {
        ws = new ServiceUtilityWS(new URL(wsdlUrl), new QName("ServiceUtilityWSSoap"));  // Exception thrown here
    } catch (MalformedURLException e) {
    }

Eu posso acessá-lo via navegador usando essas credenciais. Alguém sabe por que isso está acontecendo?

Nota:

O aplicativo é implantado no Weblogic 10. Se eu executar esse código a partir do main, a exceção não será lançada.