finding a ready-made solution to your problem is not easy. at least none exist AFAIK. due to the inherent, unknown complexity of the backing schema types associated w/ an operation's request and response, it's not possible to have such a solution.
however, putting together the correct tools, or using some open-source frameworks/libraries/tools you might be able to achieve something similar. basically you'll need to have a WSDL4J
implementation, along with a schema parser like XMLBeans
to get this working.
A tool which comes to my mind is SoapUI
. it achieves something similar - user loads a WSDL at runtime and thereafter can execute operations. the source of this tool is also available for modification under LGPL here. you'll need to strip and salvage the core functionality that suits your need. or best, build one of your own :]