@ExceptionHandler(InvalidDPoPProofException.class)
    public ModelAndView handleInvalidDPoPProofException(final HttpServletResponse req, final Exception ex) {
        return OAuth20Utils.writeError(req, OAuth20Constants.INVALID_DPOP_PROOF);
    }
Handle invalid DPoP proof exception.

@param req the req
@param ex  the ex
@return the model and view
support/cas-server-support-oidc-core-api/src/main/java/org/apereo/cas/oidc/web/controllers/token/OidcAccessTokenEndpointController.java