java - How do you identify a user in Spring using more than just the username? -

i have spring application allows administrators manage several sub-sections of application, each sub-section having own users. sub-sections loaded depending on url that's being used access app. i've had pretty simple experience using spring security , setting pretty simple custom userdetailsservice, adding roles , granting authority users, etc.

what i'd able have users allowed register under different sub-sections same username, , ideally instead of loaduserbyusername in userdetailsservice example, use more "loaduserbyusernameandsubsection". example user 'scott75' registered on subsection1.myapp.com , on subsection2.myapp.com.

i'm not looking write solution me, point me in right direction in terms of classes in spring security this. or, alternatively, tell me i'm crazy , go way, building interface around adding/removing sub-section access to/from users, or adding/removing users sub-sections.