@RequestMapping(value = "/index", method = RequestMethod.GET)
public String index(ModelMap model) {
    model.put("prename", "Hans-Peter");

    return "index";
}

<!-- Bootstrap core CSS -->
<link rel="stylesheet" href="./css/bootstrap.min.css">
<link rel="stylesheet" href="./css/zeus.css">

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.0/jquery.min.js"></script>
<script src="js/bootstrap.min.js"></script>