code: public final boolean isValid(HttpServletRequest req, String token) {
  		String storedToken = getStoredToken(req);
  		
  		if (storedToken == null)
  			return false;
  		
  		return storedToken.equals(token);
  	}
docs: Tests given token against stored one.
  @param req request used to retrieve stored cookie
  @param token token to be tested
  @return a boolean indicating if given token is valid.