Mock service that relay the request to real web service

Hello,

I have a mock service that should redirect to a real web service call and return the answer in some cases.
I still wonder how to achieve it and could not find a solution.

Is it possible to do it with Groovy, should I use a different way to do it ?

I saw that with mock service and Groovy it is also possible to change the result by accessing a database and nothing about web service calls...

Thanks in advance