One way could be to not update the model until you are attaching
again, or - kind of the same principle - update the model from the
buffer on detach. You still need some more synchronization though: the
attach/ detach models need to be synchronized in that case, and you
want to do it it such a way that you don't have a bunch of clients
waiting for it.
Eelco
On 3/2/06, Ramnivas Laddad <[EMAIL PROTECTED]> wrote:
> Spoke too soon... that doesn't work and I see why. Let me think more to
> come with a solution.
>
> -Ramnivas
>
>
> Ramnivas Laddad wrote:
> Okay... I solved my problem by making the model thread-aware...
>
> class TestModel implements IModel {
> private List<String> asyncBuffer = new ArrayList<String>();
> private List<String> underlying = new ArrayList<String>();
>
> synchronized public Object getObject(Component component) {
> underlying.addAll(asyncBuffer);
> asyncBuffer.clear();
> return underlying;
> }
>
> synchronized public void add(String message) {
> asyncBuffer.add(message);
> }
>
> public IModel getNestedModel() {
> return null;
> }
>
> public void setObject(Component component, Object object) {
> }
>
> public void detach() {
> }
> }
>
> Thanks Igor for your help.
>
> -Ramnivas
>
> Ramnivas Laddad wrote:
> So more like the Swing's single thread policy... In that case, how do I
> update model when I receive model data asynchronously? Does Wicket has
> something like EventQueue.invokeLater() or EventQueue.invokeAndWait()?
>
> -Ramnivas
>
> Igor Vaynberg wrote:
> doh, i guess i should have looked at the code before jumping to conclusions.
> i assumed you were updating the listview in the callback of the ajax
> behavior. assumption is the mother of ...
>
> you have a thread that is running unsynchronized! and updating the model of
> the component.
>
> we synchronize on the session for you so the code inside components you
> write does not have to be threadsafe. your TestModelUpdater breaks that.
>
> so the listview maybe rendering and looping over its model WHILE your
> thread adds another item to the list! that can cause all sorts of weird
> things.
>
> long story short, you cannot have a run away thread updating wicket
> components or their models. its not meant for that.
>
> -Igor
>
>
>
> On 3/2/06, Igor Vaynberg <[EMAIL PROTECTED]> wrote:
> >
> > here is what i am getting after a minute or so
> > interesting
> >
> > -Igor
> >
> > 18:09:06.263 WARN!! Exception for
> /quickstart/app?wicket:interface=:3:wmc:-1:IUnversionedBehaviorListener&wicket:behaviorId=0&random=
> 0.46824654938259036
> >
> > wicket.WicketRuntimeException: Internal Error: Could not render error page
> class wicket.markup.html.pages.InternalErrorPage
> >
> > at
> wicket.request.compound.DefaultExceptionResponseStrategy.respond
> (DefaultExceptionResponseStrategy.java:106)
> > at
> wicket.request.compound.AbstractCompoundRequestCycleProcessor.respond(AbstractCompoundRequestCycleProcessor.java:76)
> > at wicket.RequestCycle.step(RequestCycle.java :971)
> >
> > at wicket.RequestCycle.steps(RequestCycle.java:1005)
> > at wicket.RequestCycle.request(RequestCycle.java:451)
> >
> > at
> wicket.protocol.http.WicketServlet.doGet(WicketServlet.java:209)
> >
> > at javax.servlet.http.HttpServlet.service
> (HttpServlet.java:740)
> > at
> javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
> > at
> org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:358)
> > at
> org.mortbay.jetty.servlet.WebApplicationHandler.dispatch
> (WebApplicationHandler.java:294)
> > at
> org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:567)
> > at
> org.mortbay.http.HttpContext.handle(HttpContext.java:1807)
> > at
> org.mortbay.jetty.servlet.WebApplicationContext.handle
> (WebApplicationContext.java:525)
> > at
> org.mortbay.http.HttpContext.handle(HttpContext.java:1757)
> > at
> org.mortbay.http.HttpServer.service(HttpServer.java:879)
> > at
> org.mortbay.http.HttpConnection.service(HttpConnection.java
> :790)
> > at
> org.mortbay.http.HttpConnection.handleNext(HttpConnection.java:961)
> > at
> org.mortbay.http.HttpConnection.handle(HttpConnection.java:807)
> > at
> org.mortbay.http.SocketListener.handleConnection(SocketListener.java
> :218)
> > at
> org.mortbay.util.ThreadedServer.handle(ThreadedServer.java:300)
> > at
> org.mortbay.util.ThreadPool$PoolThread.run(ThreadPool.java:511)
> >
> > Caused by: java.lang.ClassCastException:
> wicket.ajax.AjaxRequestTarget$EncodingResponse
> > at
> wicket.protocol.http.WebRequestCycle.getWebResponse(WebRequestCycle.java:99)
> > at
> wicket.protocol.http.WebRequestCycle.redirectTo(WebRequestCycle.java:130)
> > at
> wicket.request.target.component.PageRequestTarget.respond
> (PageRequestTarget.java:60)
> >
> > at
> wicket.request.compound.DefaultResponseStrategy.respond(DefaultResponseStrategy.java:47)
> > at
> wicket.request.compound.AbstractCompoundRequestCycleProcessor.respond
> (AbstractCompoundRequestCycleProcessor.java :66)
> >
> > at wicket.RequestCycle.respond(RequestCycle.java:877)
> > at wicket.RequestCycle.step(RequestCycle.java:946)
> > ... 18 more
> >
> >
> >
> >
> >
> > On 3/2/06, Ramnivas Laddad <[EMAIL PROTECTED]> wrote:
> > >
> > > Sending again. Sourceforge is rejecting .zip attachment, so please
> change extension of the attached file to .zip.
> > >
> > > -Ramnivas
> > > ===
> > > Here it is... (removed lib/*.jar to cut down size).
> > >
> > >
> > > -Ramnivas
> > >
> > >
> > > Igor Vaynberg wrote:
> > > any chance you can stick those two files into a quickstart project?
> > >
> > > -Igor
> > >
> > >
> > >
> > > On 3/2/06, Ramnivas Laddad < [EMAIL PROTECTED]> wrote:
> > > > Hi,
> > > >
> > > > I now have an AJAXified listview working. However, occasionally (very
> > > > frequently on a real application and less frequently on a simplified
> > > > application :-() it crashes (program and stack trace at the end of
> this
> > > > email).
> > > >
> > > > I have an updater thread that adds new entries to the model for the
> > > > listview.
> > > >
> > > > A few observations:
> > > > 1. In the onRender() method, size returned by getViewSize() is 1, and
> > > > the index of the item to be rendered is 1. This all seems correct, as
> > > > the updater thread has just added a new item. However, item returned
> by
> > > > (ListItem)get(Integer.toString(index)) is null.
> > > >
> > > > 2. When the crashed view is re-rendered, I do no see the following
> > > > snippet in markup produced:
> > > > <script language="JavaScript"
> > > > type="text/javascript"
> > > >
> > > >
> src="/resources/wicket.ajax.AbstractDefaultAjaxBehavior/wicket-ajax.js">
> > > > </script>
> > > > As a result, no AJAX updates take place.
> > > >
> > > > While it seems to be concurrency-related bug, the model itself as I
> have
> > > > written seems thread-safe.
> > > >
> > > > Thanks.
> > > >
> > > > -Ramnivas
> > > >
> > > > Source code:
> > > > ==========
> > > > public class AJAXListHome extends WebPage {
> > > > public AJAXListHome() {
> > > > TestModel model = new TestModel();
> > > >
> > > > WebMarkupContainer wmc = new WebMarkupContainer("wmc");
> > > > add(wmc);
> > > > ListView testListView = new TestListView("dates", model);
> > > > wmc.add(testListView);
> > > > wmc.add(new
> AjaxSelfUpdatingTimerBehavior(Duration.seconds(2)));
> > > >
> > > > new Thread(new TestModelUpdater(model, testListView)).start();
> > > > }
> > > > }
> > > >
> > > > class TestListView extends ListView {
> > > > public TestListView(String id, TestModel model) {
> > > > super(id, model);
> > > > }
> > > >
> > > > @Override
> > > > protected void populateItem(ListItem item) {
> > > > String date = (String)item.getModelObject();
> > > > item.add(new Label("date", date));
> > > > }
> > > > }
> > > >
> > > > class TestModel implements IModel {
> > > > private List<String> underlying = new ArrayList<String>();
> > > >
> > > > synchronized public Object getObject(Component component) {
> > > > return underlying;
> > > > }
> > > >
> > > > synchronized public void add(String message) {
> > > > underlying.add(message);
> > > > }
> > > >
> > > > public IModel getNestedModel() {
> > > > return null;
> > > > }
> > > >
> > > > public void setObject(Component component, Object object) {
> > > > }
> > > >
> > > > public void detach() {
> > > > }
> > > > }
> > > >
> > > > class TestModelUpdater implements Runnable {
> > > > private TestModel model;
> > > > private Component view;
> > > >
> > > > static int counter = 0;
> > > >
> > > > public TestModelUpdater(TestModel model, Component view) {
> > > > this.model = model;
> > > > this.view = view;
> > > > }
> > > >
> > > > public void run() {
> > > > while(true) {
> > > > model.add("string" + counter);
> > > > // notifying model doesn't seem to be required; should it
> > > > be notified?
> > > > // view.modelChanged();
> > > > counter++;
> > > > try {
> > > > TimeUnit.SECONDS.sleep(1);
> > > > } catch (InterruptedException ignored) {
> > > > }
> > > > }
> > > > }
> > > > }
> > > > ===
> > > > Stack trace:
> > > > Root cause:
> > > >
> > > > java.lang.NullPointerException
> > > > at
> wicket.markup.html.list.ListView.renderItem(ListView.java:606)
> > > > at
> wicket.markup.html.list.ListView.onRender(ListView.java
> :567)
> > > > at wicket.Component.render(Component.java:1516)
> > > > at
> wicket.MarkupContainer.renderNext(MarkupContainer.java:1206)
> > > > at
> wicket.MarkupContainer.renderComponentTagBody(MarkupContainer.java:875)
> > > > at wicket.MarkupContainer.onComponentTagBody
> (MarkupContainer.java:795)
> > > > at
> wicket.Component.renderComponent(Component.java:1602)
> > > > at wicket.MarkupContainer.onRender(MarkupContainer.java:805)
> > > > at wicket.Component.render(Component.java:1516)
> > > > at wicket.MarkupContainer.renderNext
> (MarkupContainer.java:1206)
> > > > at
> wicket.MarkupContainer.renderComponentTagBody(MarkupContainer.java:875)
> > > > at
> wicket.MarkupContainer.onComponentTagBody(MarkupContainer.java:795)
> > > > at wicket.Component.renderComponent(Component.java
> :1602)
> > > > at wicket.MarkupContainer.onRender(MarkupContainer.java:805)
> > > > at wicket.Component.render(Component.java:1516)
> > > > at
> wicket.MarkupContainer.renderNext(MarkupContainer.java:1206)
> > > > at wicket.MarkupContainer.renderAll
> (MarkupContainer.java:822)
> > > > at wicket.Page.onRender(Page.java:846)
> > > > at wicket.Component.render(Component.java:1516)
> > > > at wicket.Page.doRender(Page.java:390)
> > > > at
> > > >
> wicket.request.target.component.BookmarkablePageRequestTarget.respond
> (BookmarkablePageRequestTarget.java:224)
> > > > at
> > > >
> wicket.request.compound.DefaultResponseStrategy.respond(DefaultResponseStrategy.java:47)
> > > > at
> > > >
> wicket.request.compound.AbstractCompoundRequestCycleProcessor.respond(AbstractCompoundRequestCycleProcessor.java
> :66)
> > > > at
> wicket.RequestCycle.doProcessEventsAndRespond(RequestCycle.java:824)
> > > > at
> wicket.RequestCycle.processEventsAndRespond(RequestCycle.java:851)
> > > > at wicket.RequestCycle.step(RequestCycle.java:931)
> > > > at wicket.RequestCycle.steps (RequestCycle.java:1005)
> > > > at wicket.RequestCycle.request(RequestCycle.java:451)
> > > > at
> wicket.protocol.http.WicketServlet.doGet(WicketServlet.java:208)
> > > > at
> javax.servlet.http.HttpServlet.service(HttpServlet.java:740)
> > > > at
> javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
> > > > at
> org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:358)
> > > > at
> > > >
> org.mortbay.jetty.servlet.WebApplicationHandler.dispatch(WebApplicationHandler.java
> :294)
> > > > at
> org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:567)
> > > > at
> org.mortbay.http.HttpContext.handle(HttpContext.java:1807)
> > > > at
> > > >
> org.mortbay.jetty.servlet.WebApplicationContext.handle(WebApplicationContext.java
> :525)
> > > > at
> org.mortbay.http.HttpContext.handle(HttpContext.java:1757)
> > > > at
> org.mortbay.http.HttpServer.service(HttpServer.java:879)
> > > > at
> org.mortbay.http.HttpConnection.service(HttpConnection.java:790)
> > > > at org.mortbay.http.HttpConnection.handleNext
> (HttpConnection.java:961)
> > > > at
> org.mortbay.http.HttpConnection.handle(HttpConnection.java:807)
> > > > at
> org.mortbay.http.SocketListener.handleConnection(SocketListener.java:218)
> > > > at org.mortbay.util.ThreadedServer.handle(
> ThreadedServer.java:300)
> > > > at
> org.mortbay.util.ThreadPool$PoolThread.run(ThreadPool.java:511)
> > > >
> > > >
> > > >
> > > >
> > > >
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