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  1. Wicket
  2. WICKET-5460

onBeforeRender called too early on stateless page



    • Bug
    • Status: Resolved
    • Major
    • Resolution: Fixed
    • 6.12.0, 7.0.0-M1
    • 6.14.0, 7.0.0-M1
    • wicket
    • None


      I'm having a problem with a ListView that displays an outdated list.
      In my test, the ListView uses a Model that returns a static variable just to make sure the model is independent from any page instance. As far as I can tell, this problem has nothing to do with the model, but with the way Wicket prepares for a request listener invocation.

      The exact setup is this:

      • the page contains a ListView and (outside of the list) a Link that
        adds an item to the list in its onClick(). The list itself is stored
        in a static variable.
      • the page is stateless
      • the page's components are created in onInitialize()

      The list doesn't show the most recently added item. Reloading the
      original page shows the correct list. Note that by "reloading" I mean
      entering the page's original URL since the browser's address bar now contains the request listener URL due to the page being stateless.

      This is how I think is happens:

      • Initially rendering the page works fine. The page is then discarded
        since it's stateless.
      • Clicking on the link creates a new page instance to invoke the
        link's request listener.
      • IPageAndComponentProvider.getComponent() cannot find the link yet
        since it is not created until onInitialize() has been called.
      • as a consequence, it calls page.internalInitialize() and
      • this creates the link, but it also creates the ListView and prepares
        it for rendering. This in turn polls the ListView's model and creates
        list items. It also marks the ListView as "prepared for render", which
        is the crucial point.
      • The link's request listener runs and adds an item to the list.
      • After the request listener handler, the page render handler runs
      • That handler renders the page, including the ListView
      • ... but it doesn't call onBeforeRender() on the ListView anymore,
        because it's already marked as "prepared for render"! So it doesn't
        pick up the new, up-to-date list from its model.

      I'm not sure if I'm "doing it wrong", but then it doesn't seem quite
      right that onBeforeRender() gets called before invoking the listener,
      but not actually before rendering. There's probably some kind of logic
      behind the decision to run onBeforeRender() only when this hasn't yet
      happened, right? Is there a general way to "unprepare" the component
      in onClick()?

      Re: #internalPrepareForRender(false) should not mark the page as rendered (thus the false parameter).

      The problem is, I think, not that the component is being marked as
      rendered, but as prepared for render. From class Component:

      protected void onBeforeRender()
      setFlag(FLAG_PREPARED_FOR_RENDER, true);

      Note the first line. This causes subsequent invocations of
      internalBeforeRender() to skip the relevant part.


        1. beforerender-bug.zip
          25 kB
          Martin Geisse



            svenmeier Sven Meier
            martin geisse Martin Geisse
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