JWt

If you don't want your UI to freeze or timeout you'll need to enable updates and make a new thread.

With Java 8 lambdas it's pretty simple.

WApplication.getInstance().enableUpdates(true);

https://github.com/jahnje/delcyon-capo/blob/master/java/com/delcyon/capo/webapp/widgets/WWorker.java

The update method more or less calls the WApplication.triggerUpdate() method which causes JWT's magic to happen between threads.

Here's an example using this WWorker class to run a pdf report and trigger progress bar changes wile it loads.

private void runReport()
    {
        if (worker.isRunning())
        {
            worker.interrupt();
            return;
        }
        DocketWarrantsReport rptWarrants = new DocketWarrantsReport();
        btnRun.setText("Cancel");
        prgBar.setHidden(false);
        anchorResults.setHidden(true);
        prgBar.setValue(prgBar.getMinimum());
        WCursorState.wait.setCursourStateOn(WApplication.getInstance().getRoot());
        worker.run(() -> {
            try
            {
                prgBar.valueChanged().addListener(prgBar, () -> worker.update());
                bosWarrantReport = rptWarrants.getWarrantsForHearingsPDF(dtpBeginDate.getIntegerDate(), dtpEndDate.getIntegerDate(), chkInCounty.getBooleanValue(), chkMayAppear.getBooleanValue(), prgBar);                
                prgBar.setValue(prgBar.getMaximum());
                anchorResults.setHidden(true);
                anchorResults.open();
                worker.update();
            }
            catch (InterruptedException e)
            {
                // Do nothing, it's just the user hitting cancel
            }
            catch (Exception e)
            {
                JOApplication.exception(Level.WARNING, e.getMessage(), e, worker.getOwnerApplication());
            }
            prgBar.setHidden(true);
            btnRun.setText("Run");
            WCursorState.initial.setCursourStateOn(WApplication.getInstance().getRoot());
            worker.update();
        });

    }

also, apache has an httpClient you can use that pretty popular for access external web resources. Or you can use the built in HttpURLConnection if it's not too complicated.

Ah, nice --- thank you! Will give your WWorker a try this weekend.

Just a little followup for anybody else who visits this thread in the future. (Thanks again for your assistance, Jeremiah)

Since I'm using Groovy, I decided to use the Http Builder NG library: https://github.com/dwclark/http-builder-ng .

I made a method in my WApplication object:

    def getJSON(String url, Map<String, String> params, Closure<Object> callback) {
        Thread.start {
            http.get {
                request.uri.path = url
                request.uri.query = params
                response.success { res, Object data ->
                    def lock = getUpdateLock()
                    try {
                        callback(data)
                        triggerUpdate()
                    } finally {
                        lock.release()
                    }
                }
            }
        }
    }

And here is an example of calling it, such as in a button click listener:

        getJSON("https://api.giphy.com/v1/gifs/random", [api_key: "xxxxxx", tag: "cats"]) { result ->
            // change UI here, based on converted JSON 'result'
        }

Of course I'll eventually have to add a way to handle API failures / network exceptions properly, but for my current experiments this will do.

One of the reasons there's no httpclient in jwt, is that there's a ton of libraries in java that handle this pretty well. We felt that there wasn't an easy solution for C Wt yet.

Wim.