PreAuthenticationProcessingFilter unique issue

[surfer]

Hello all,
I have implemented the remember me (persistence token based) service and that i working fine along with UsernamePasswordAuthenticationFilter. However, after a user logs in, if the user is an administrator, he/she should be able to log in as someone else just by providing JUST the username. The application should behave as if the original user has signed in. I think PreAuthenticationFilter would suffice my needs, just a theory. Any help is appreciated.

[surfer]

Posting the solution just in case if anyone is facing the same issue:
Create new PreAuthenticatedAuthenticationToken token

here's the code:

Collection<GrantedAuthority> authorities = new ArrayList<GrantedAuthority>();
GrantedAuthority g1 = new GrantedAuthorityImpl("SOMEROLE_SOMEUSER");
authorities.add(g1);

PreAuthenticatedAuthenticationToken authentication =
new PreAuthenticatedAuthenticationToken("userid", "",authorities);

authentication.setAuthenticated(true);

SecurityContextHolder.getContext().setAuthenticati on(authentication);
request.getSession().setAttribute("SPRING_SECURITY _LAST_USERNAME", "userid");

rememberMeServices.loginSuccess(request, response, authentication);
customAuthenticationSuccessHandler.onAuthenticatio nSuccess(request, response, authentication);

- that's it....