code: public static String getUserIdFromSecurityContext() {
  		final SecurityContext context = SecurityContextHolder.getContext();
  		if (context != null) {
  			final Authentication authentication = context.getAuthentication();
  			if (authentication != null) {
  				return authentication.getPrincipal().toString();
  			}
  		}
  		return null;
  	}
docs: Gets the user id from security context.
  
  @return the user id from security context