I was probably overly wordy & not very clear on the details of our problem. The client side isn't the issue: We display the client progress bar via JavaScript & it's been working fine for a number of years. Our challenge is on the server side: Managing the background task in a separate thread. We have three basic requirements for the background task. It must:
1. Be cancellable. 2. Report its outcome (success/failure/warning). 3. Report incremental progress. Graceful handling of the thread outcome is an unexpectedly a tough nut to crack. The vast majority of examples we've seen use the Runnable interface (which doesn't help us, as it can't be canceled or return a value), rather than Callable interface (which meets our needs, but doesn't seem to play well with Wicket, since java.util.concurrent.FutureTask isn't Serializable). From: Martin Grigorov <mgrigo...@apache.org> To: "users@wicket.apache.org" <users@wicket.apache.org> Date: 05/05/2014 03:32 PM Subject: Re: Progress Bar Hi, On Mon, May 5, 2014 at 7:18 PM, Richard W. Adams <rwada...@up.com> wrote: > We have a requirement to implement a progress bar for long-running server > operations. We can't use the code at > https://github.com/wicketstuff/core/wiki/Progressbar, because it doesn't > meet our corporate user interface look-and-feel standards. > Have you considered providing your own .css ? https://github.com/wicketstuff/core/blob/wicket-6.x/jdk-1.6-parent/progressbar-parent/progressbar/src/main/java/org/wicketstuff/progressbar/ProgressBar.java#L109 > > So, we started our own implementation. Our test page contains these > methods below (the TestExecutor below class implements > Callable<ExecutorResult>). > > > //---------------------------------------------------------------------------------------------- > private Component createButton() { > return new AjaxButton("start-button") { > private static final long serialVersionUID = -1; > > @Override protected void onSubmit(final AjaxRequestTarget > ajax, final Form<?> form) { > > final ExecutorService service = Executors. > newSingleThreadExecutor(); > try { > final ProgressBarTestPage page = > ProgressBarTestPage.this; > final TransactionData data = new > TransactionData (page.getId(), false); > final TestExecutor executor = new > TestExecutor(data, getPermissions()); > > executor.addListener(page); // Request > notification when done > future = service.submit(executor); // > Begin execution > progressBarUpdater.start(ajax, executor); > // Start polling for progress > > } catch (final Exception ex) { > throw new RuntimeException(ex); > } > service.shutdown(); // Terminate gracefully > (VM probably > } // won't exit if we fail to do this) > }; > } > > //---------------------------------------------------------------------------------------------- > /** > Observer Pattern method to let us know when the task is done so we can > check how things went. > */ > @Override public void executionComplete(final EnmCallableExecutor > executor) { > > try { > if (!future.isCancelled()) { // > Unless execution was canceled > final ExecutorResult result = future.get(); // > Get the outcome > System.out.println(result); > /* > * TODO: Show success or error message > */ > } > } catch (final Exception ex) { > ex.printStackTrace(); > } > } > > The ProgessBarUpdater class has this method: > > > //---------------------------------------------------------------------------------------------- > /** > * Displays the progress bar & begins the polling. We don't start the > polling until > * explicitly told to do, for efficiency purposes. > * @param ajax The Ajax request wrapper. > * @param reporter The object to query for progress data. > */ > public void start(final AjaxRequestTarget ajax, final ProgressReporter > reporter) { > > add(new AjaxSelfUpdatingTimerBehavior(Duration.seconds(2)) { > private static final long serialVersionUID = 1L; > > @Override protected void onPostProcessTarget(final > AjaxRequestTarget ajax) { > > final Progress progress = reporter.getProgress(); > final String script = // Build > script to update > ProgressScript.build(progress); // > progress bar > ajax.appendJavascript(script); > if (progress == null) { // If > operation is finished > final ProgressBarUpdater updater = > ProgressBarUpdater.this; > updater.remove(this); // > Stop timer to prevent > ajax.addComponent(updater); // pointless > polling > } > } > }); > ajax.addComponent(this); > } > > The page also contains a Future object so we can check the result after > the thread finishes: > > private Future<ExecutorResult> future; > > __________________________________________ > > Having said all that, here's the problem: When I click the page's button, > Wicket throws this error: > > Unable to serialize class: java.util.concurrent.FutureTask > > The FutureTask object, I believe, is coming from the service.submit call > whose return value we store in our Future variable. > > Does anyone know how to get around this roadblock? > > > > ** > > This email and any attachments may contain information that is > confidential and/or privileged for the sole use of the intended recipient. > Any use, review, disclosure, copying, distribution or reliance by others, > and any forwarding of this email or its contents, without the express > permission of the sender is strictly prohibited by law. 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