No, I don't cover OpenID in the book...that's one of those ancillary topics that didn't make the cut. It's a good topic, though. In fact, just today I found myself needing to know more about Spring Security's OpenID support and had to go research it a bit.
Believe it or not, I don't know *everything* about Spring..and even some things I once knew have slipped out of my aging brain. You know they say there are two things that go when you get older: Your memory and...I can't remember what the other thing was.