Get UserDetails object from Security Context in Spring MVC controller

If you already know for sure that the user is logged in (in your example if /index.html is protected):

UserDetails userDetails =
 (UserDetails)SecurityContextHolder.getContext().getAuthentication().getPrincipal();

To first check if the user is logged in, check that the current Authentication is not a AnonymousAuthenticationToken.

Authentication auth = SecurityContextHolder.getContext().getAuthentication();
if (!(auth instanceof AnonymousAuthenticationToken)) {
        // userDetails = auth.getPrincipal()
}

Let Spring 3 injection take care of this.

Thanks to tsunade21 the easiest way is:

 @RequestMapping(method = RequestMethod.GET)   
 public ModelAndView anyMethodNameGoesHere(Principal principal) {
        final String loggedInUserName = principal.getName();

 }