public Response handle(MessageContext mc, OAuthDataProvider dataProvider) {
HttpServletRequest request = mc.getHttpServletRequest();
try {
OAuthMessage oAuthMessage =
OAuthUtils.getOAuthMessage(mc, request, REQUIRED_PARAMETERS);
new DefaultOAuthValidator().checkSingleParameter(oAuthMessage);
RequestToken token = dataProvider.getRequestToken(oAuthMessage.getToken());
if (token == null) {
throw new OAuthProblemException(OAuth.Problems.TOKEN_REJECTED);
}