Convert old shared services token generation API code to new version

Can you please help me to convert the token generation code as per new version of shared services? We were using cssconfig file to generate the token for the logged in user. Since cssconfig file is gone in 11.1.2.4, I am not able to generate the token.

old way of code generation -

private Map<String, String> initialContext = new HashMap<String, String>();

CSSSystem system = CSSSystem.getInstance(initialContext, getConfigFile(), "test");

private CSSAPIIF css = system.getCSSAPI();

initialContext.put(CSSAPIIF.SECURITY_AGENT_LOGIN_NAME, "USERNAME");

String tokenStr = null;

CSSUserIF css_user = css.authenticate(initialContext);

tokenStr = css_user.getToken();

return tokenStr;

Doe anyone know how to generate the token for user in new API.