Note: I could not find a straight-forward answer to this problem so I will document my solution below as an answer.
I generated the server-side part
When I had this problem, it was caused by using the wrong URL.
I used http://localhost:8080/axis/services/AdminWebService?wsdl instead of http://localhost:8080/axis/services/AdminService?wsdl.
http://localhost:8080/axis/services/AdminWebService?wsdl
http://localhost:8080/axis/services/AdminService?wsdl
AdminWebService must be changed to AdminService.
AdminWebService
AdminService