issueAuthenticateChallenge redirect

Hi, i'm making a auth extension and when the password is incorrect or the username doesn't exist, i call the function, setRequiresChallenge(true), on the authenticate function. but my issueAuthChallenge function is never called. Please help me, thank you.

@Override
	public void issueAuthenticationChallenge(HttpServletRequest httpRequest, HttpServletResponse httpResponse) throws AuthenticatorException {
	_securityLogger.info("Customized Authentication Called issueAuthenticationChallenge");
	
	String urlString= "http://localhost/";
	try{
		httpResponse.sendRedirect(urlString);
 }
 catch(IOException e)
 {
 e.printStackTrace();
 }
	}