Writing custom login for Spring Security (Grails) -

i'm trying write custom login spring security. if use form generated, works, when try manually redirect link (j_spring_security_check) method controller, tells me: sorry, not able find user username , password. here's did:

def config = springsecurityutils.securityconfig         def j_username = params.j_username         def j_password = params.j_password         redirect(url: "${request.contextpath}${config.apf.filterprocessesurl}", params: [j_username: j_username, j_password: j_password]) 

i've printed out myselft params, correct, doing wrong?