j_security_check .. how to check encrypted password ..

[sarim raza]

problem is in databse i have username and password (these are encrypted)..
in the login page, user enters the actual password and submits ... how can i first use my encrypt() method to encrypt the password to match those stored in database.. reason why i cant do that is since login page uses j_security_check (tomcats mechanism . to check for username, pasword).
<form method=post action=j_security_check>
thanks