gistfile1.txt

public class JWTAuthenticationEntryPoint implements AuthenticationEntryPoint {

    @Override
    public void commence(HttpServletRequest request, HttpServletResponse response, AuthenticationException exception)
            throws IOException, ServletException {
        response.setStatus(403);
        response.setContentType(MediaType. APPLICATION_JSON_VALUE);

        String message;
        if (exception.getCause() != null) {
            message = exception.getCause().getMessage();
        } else {
            message = exception.getMessage();
        }
        byte[] body = new ObjectMapper().writeValueAsBytes(Collections.singletonMap("error", message));
        response.getOutputStream().write(body);
    }

}