Spring Security Auto Authenticate User

Hello,

I have a security flow where I'm receiving an xml that I need to verify.  If it passes that logic then I do a select on my users table (UserDetail implementation) if they exist I can log them in using the below, but if they don't exists I need to Auto Authenticate them. Would I just do an insert into the users table in my super.getAuthenticationManager().authenticate method and return the newly created UserDetails object?

    public class XMLAuthenticationFilter extends AbstractAuthenticationProcessingFilter{
          public XMLAuthenticationFilter() {
              super("/xml_security_check");
          }
   
          @Override
          public Authentication attemptAuthentication(HttpServletRequest request,
                      HttpServletResponse response) throws AuthenticationException,
                      IOException, ServletException {
                
                       GrantedAuthority[] grantedAuthorities = new GrantedAuthority[] { new GrantedAuthorityImpl("ROLE_USER")};
                       UsernamePasswordAuthenticationToken token = new UsernamePasswordAuthenticationToken("username", "userpwd", grantedAuthorities);
                  request.getSession();
                  token.setDetails(new WebAuthenticationDetails(request));
                  Authentication authenticatedUser = super.getAuthenticationManager().authenticate(token);
                  SecurityContextHolder.getContext().setAuthentication(authenticatedUser);
                  request.getSession().setAttribute(HttpSessionSecurityContextRepository.SPRING_SECURITY_CONTEXT_KEY, SecurityContextHolder.getContext());
                  return authenticatedUser;
                 }
    }