Add a parameter called InvocationStatus in the Authenticate method. This parameter receives an object of type ExternalServiceInvocationStatus, which we previously defined.
Define_Map For(*INPUT) Class(#ExternalServiceInvocationStatus) Name(#InvocationStatus) Pass(*BY_REFERENCE) Mandatory(*NULL)
And add the following code to read the status from the response object after #Request.DoGet:

• Get the request status
  If (#InvocationStatus *IsNot *Null)
     #InvocationStatus.FromHttpResponse( #Request.Response )
  Endif
  The complete source code of the Authenticate method after the adjustments (new lines are highlighted in yellow):
  Mthroutine Name(Authenticate)
     * Parameters
     Define_Map For(*INPUT) Class(#PRIM_DC.UnicodeString) Name(#Domain)
     Define_Map For(*INPUT) Class(#PRIM_DC.UnicodeString) Name(#UserName)
     Define_Map For(*INPUT) Class(#PRIM_DC.UnicodeString) Name(#Password)
     Define_Map For(*RESULT) Class(#PRIM_DC.UnicodeString) Name(#Result)
     Define_Map For(*INPUT) Class(#ExternalServiceInvocationStatus) Name(#InvocationStatus) Mandatory(*NULL) Pass(*BY_REFERENCE)
     * Variables
     Define_Com Class(#XPRIM_UriBuilder) Name(#Url)
     Define_Com Class(#XPRIM_HttpRequest) Name(#Request)
     Define_Com Class(#XPRIM_RandomAccessJsonReader) Name(#Json)
     * Setup the URL's base properties
     #COM_SELF.SetupUrlBuilder Urlbuilder(#Url)
     * Add the 'authenticate' path component
     #Url.AddPathComponent Pathcomponent('authenticate')
     * Add the form parameters
     #Url.AddQueryString( 'domain' 'syd' )
     #Url.AddQueryString( 'username' 'tony' )
     #Url.AddQueryString( 'password' 'test' )
     * Execute the HTTP request
     #Request.DoGet Url(#Url)
     * Get the authentication result
     #Json.SetSourceHttpResponse( #Request.Response )
     #Result := #Json.ReadStringWithName( 'result' )
     * Get request status
     If (#InvocationStatus *IsNot *Null)
        #InvocationStatus.FromHttpResponse( #Request.Response )
     Endif
  Endroutine
   
  Next: Testing the User Authenticate Service