OS Login id in Web Dynpro Abap

Hi all

I want to get system OS login id in WDA. Please sugest me to get. I got this method but it did not work in WDA, which is working fine in ABAP.

DATA: username TYPE string.

CALL METHOD CL_GUI_FRONTEND_SERVICES=>GET_USER_NAME

   CHANGING

     USER_NAME    = username

   EXCEPTIONS

     CNTL_ERROR   = 1

     ERROR_NO_GUI = 2

     others       = 3.

IF SY-SUBRC ne 0.

MESSAGE ID SY-MSGID TYPE SY-MSGTY NUMBER SY-MSGNO

            WITH SY-MSGV1 SY-MSGV2 SY-MSGV3 SY-MSGV4.

ENDIF.

CALL METHOD CL_GUI_CFW=>UPDATE_VIEW

                             EXCEPTIONS

                               CNTL_SYSTEM_ERROR = 1

                               CNTL_ERROR        = 2

                               others            = 3.

Thanks in advance

Indiranjthn