Programmatic login

[Crnobog Veter]

Hi guys.
 
I would like to automatically login the user, that has just confirmed his newly 
created account.
 
I tried with the
SecurityUtils.getSubject().login method, but the problem is that i do not have 
the password avilable at this point as the one in the db is hashed and 
therefore unusable for UsernamePasswordToken.
 
Any ideas on how to pull this one off?
 
Thank you for your answers and best regards.
 
JJ