Creating facebook connection from access token

Hello,
I'm trying to develop an Android apps that uses native facebook toolkit to authenticate the user.

After the user has logged in I've an auth token and I can send it to my server side app to do operations on the behalf of the user.

But I would like to open a (spring social) connection using that token, is it possible?

I should be able to using a code similar to this:

I should have all the data made except the expire value: anybody knows how to decode it to correctly complete this procedure?

Thanks