//setup the callback handler
final CallbackHandler callbackHandler;
if (appClientData != null && appClientData.getCallbackHandler() != null && !appClientData.getCallbackHandler().isEmpty()) {
try {
final Class<?> callbackClass = classIndex.classIndex(appClientData.getCallbackHandler()).getModuleClass();
callbackHandler = new RealmCallbackWrapper((CallbackHandler) callbackClass.newInstance());
} catch (ClassNotFoundException e) {
throw AppClientLogger.ROOT_LOGGER.couldNotLoadCallbackClass(appClientData.getCallbackHandler());
} catch (Exception e) {
throw AppClientLogger.ROOT_LOGGER.couldNotCreateCallbackHandler(appClientData.getCallbackHandler());
}