That's awesome! I know that there's quite a bit of interest in a Spring Social module for Google.
I'll take a closer look at your work soon, but for now I noticed that the connection support is based on OAuth 2. Very good move! I know that Google also supports OAuth 1, but as I recall from having looked at it awhile back, their OAuth 1 implementation was a bit unusual. So, I'm happy to see that you chose to go with OAuth 2.
The big challenge with a Google module is that Google has *SO* many APIs, so building out the API binding will be a big undertaking. But it's a great start and is obviously it'll be good to plug in the Google+ API binding in here when Google finally publishes the Google+ API.
Spring Social Project Lead