Alter response throught proxy

I use SoapUI to test a certain webservice. The wsdl the webservice returns is not opt开发者_JS百科imal for SoapUI, so I want to modify the response. Since the wsdl is still subject to change, i want the connection to go through a custom proxys, which modifies the response if the response is from certain pages. Other pages should be put through untouched.

How would I create such proxy in Java? I want to do as few HTTP specific logic in the proxy, just alter the response of some pages.