A SOAP based Web Service can be defined as follows:
@WebService(name = "MyService")
@WebContext(contextRoot = "/myRoot", authMethod = "BASIC", secureWSDLAccess = true)
@EndpointConfig(configName = "Standard WSSecurity Endpoint")

Now the WSDL cannot be accessed without BASIC authentication.

Therefore, it would be fine, if you could provide a checkbox within the dialog "Select WSDL", so that username and password could be prompted. Just as the checkbox below "Request details" in the main window.