What is the relationship of UserDetail and Authentication

[richardsang2004]

According to the java doc, the UserDetail holds information and later on to be stored inside the Authentication.
I am using my own AuthenticationDao impl, and it has a method loadxxx to return a Usertail object. If I have another object I need to use, how would I attack to the UserDetail so later I can get it from Authentication?

[Ben Alex]

UserDetails is an interface.

Your AuthenticationDao can return any concrete implementation of UserDetails that you like. We suggest returning the included User, or a subclass, but there is nothing wrong with returning your own implementation instead.