I found that - in your samples - you used an extends of ResourceResolveSpi when verifing(OfflineResourceResolve.java). But I still don't understand ...
Have you read: <http://xml.apache.org/security/Java/resolver.html>?
It's an introduction into the Resolvers.
Basically what they do is take a URI and somehow find the data that belongs to that URI. There are Resolvers that use URLs to fetch the data and return it, there are Resolvers that interpret the URI as an ID and go search the local document.. it's entirely up to you.
URI goes in, signed content comes out. Normally though, with a proper URI you shouldn't have any problem.. it will cycle through the standard ones until he can find one to use.
Can you try to just run the example and see what it does?
Erwin
