Loading Resty-GWT

How can I show load widget, when client send json on server.

From example in GWTP exmaple I found such method

/**
* We display a short lock message whenever navigation is in progress.
*
* @param event The {@link LockInteractionEvent}.
*/
@ProxyEvent
public void onLockInteraction(LockInteractionEvent event) {
getView().setLoading(event.shouldLock());
}

How do I show in the loading resty-gwt, when it sent the request? Can I use onLockInteraction with resty-gwt?

You can use RestyGWT custom Dispatcher to track request lifecycle. Dispatcher can be configured manually or using annotations (https://resty-gwt.github.io/documentation/restygwt-user-guide.html). Example setting it manually:

RootRestService rest = GWT.create(RootRestService.class);
((RestServiceProxy) rest).setDispatcher(new DefaultDispatcher() {
    @Override public Request send(Method m, RequestBuilder rb) throws RequestException {
        RequestCallback callback = rb.getCallback();
        rb.setCallback(new RequestCallback() {
            @Override public void onResponseReceived(Request req, Response res) {
                log.info("request success (stop event)");
                callback.onResponseReceived(req, res);
            }
            @Override public void onError(Request req, Throwable ex) {
                log.info("request error (stop event)");
                callback.onError(req, ex);
            }
        });
        try {
            log.info("request initialized (start event)");
            return request = super.send(m, rb);
        } finally {
            log.info("request fail to initialize error (stop event)");
        }
    }
});

Instead of logging, you can send an event using the eventBus, and use this event to keep track of the number of active request, and finally show a loading indicator if the number of active request is grater than 0.