Overriding Password in JDBC Realm

[Emsley, I (Iain)]

I'm trying to implement a JDBC realm to compare a cookie against a
database to authenticate an identity but my current application falls
over trying to get a password where one doesn't exist (they are checked
earlier on in the cycle in another section of the programme). 
 
Is there a way of overriding the getPassword which the Realm appears to
want or am I best off trying to put a custom realm together?
 
Thanks, 
 
Iain
 
Iain Emsley