sample.java

 
 Ion.with(this)
    .load("https://url")
    .basicAuthentication("user", "pass")
    .asJsonObject()
    .setCallback(new FutureCallback<JsonObject>() {
        @Override
        public void onCompleted(Exception e, JsonObject result) {
            if (e != null) {
              // Error loading url
              return;
            }
            
            //
            accessToken = result.get("access_token").getAsString();
            //
        }
    });