U2F JavaScript for Client Side in GWT (JSNI)

Question

I'm trying to get response from U2F Token in GWT project using this source code:

public class Test implements EntryPoint {

    @Override
    public void onModuleLoad() {
         Window.alert("Alert 3:"+u2FTest());
    }

    public static native String u2FTest()/*-{
    var respond = {rep: "Clear"};
    var RegistrationData = {"challenge":"dG7vN-E440ZnJaKQ7Ynq8AemLHziJfKrBpIBi5OET_0",
                            "appId":"https://localhost:8443",
                            "version":"U2F_V2"};
 $wnd.u2f.register([RegistrationData], [],
  function(data) {if(data.errorCode) {
        alert("U2F failed with error: " + data.errorCode);
        return;
    }

    respond.rep=JSON.stringify(data);
    alert("Alert 1: "+respond.rep); 
});
 alert("Alert 2: "+respond.rep);
 return respond.rep;
}-*/;

}

for some reasons I get The Alerts like so:

(Alert 2) first with "Clear" result
(Alert 3) with "Clear"
(Alert 1) with Token response

Normally I've to get (Alert 1) with Token response then 2,3. So how can I stop execution until I'll get the token response Thank you,

I need I way to wait until I'll receive tha **JSON** object from Token — Abdessamad Doughri, Mar 27 '15 at 12:09

score 2 · Accepted Answer · answered Mar 27 '15 at 16:24

Embrace asynchronicity!

public static native void u2FTest(com.google.gwt.core.client.Callback<String, Integer> callback) /*-{
  // …
  $wnd.u2f.register(regReqs, signReqs, $entry(function(response) {
    if (response.errorCode) {
      callback.@com.google.gwt.core.client.Callback::onFailure(*)(@java.lang.Integer::valueOf(I)(response.errorCode));
    } else {
      callback.@com.google.gwt.core.client.Callback::onSuccess(*)(JSON.stringify(response));
    }
  }));
}*-/;

(don't forget to wrap callbacks in $entry() so that exceptions are routed to the GWT.UnhandledExceptionHandler, if there's one)

U2F JavaScript for Client Side in GWT (JSNI)

1 Answers1