authenticator-example.js

AuthenticationFlowError = Java.type("org.keycloak.authentication.AuthenticationFlowError");

function authenticate(context) {
    LOG.info(script.name + " --> trace auth for: " + user.username);
    if (user.username === "fail") {
        context.failure(AuthenticationFlowError.INVALID_USER);
        return;
    }
    context.success();
}