Hi Robert.
Are you looking for a reason to use PreThreadValue? Or do you just want to
have a page/component level property that you can access for the life of
the request?
In a page or component you just declare the variable and let tapestry do
it's magic in the background.
private int widgetRenderCount = 0;
void afterRender() {
++widgetRenderCount;
log.debug("{} widgets have now rendered in this request!",
count);
}
If you want to use it in a singleton service then you need to do the
plumbing.
Josh
On Wed, Nov 28, 2012 at 2:32 PM, Robert Hailey <rhai...@allogy.com> wrote:
>
> I've read the "everyone out of the pool" blog post, but have not been able
> to find an example of how to best use per-thread value on a page or service
> (seems like what's provided is an internal tapestry case).
>
> As a (lazy?) tapestry developer, my first thought is to try this:
>
> @Inject
> private PerThreadValue<Integer> widgetRenderCount;
>
> Which probably isn't the expected use-case, because it doesn't work: "no
> service implements PerThreadValue interface" (or thereabout)
>
> I then though I was probably looking one abstraction layer too deep (as
> the article does talk about transparent perthread access)... so then I
> thought of this:
>
> @Inject
> @PerThread
> private Integer widgetRenderCount;
>
> Which made a degree of sense because "Persist" is deprecated, but no such
> annotation exists.
>
> So then I thought I could create my own perthreadvalue-providing service
> (to realize the first example) like this:
>
> public void contributeMasterObjectProvider(
> OrderedConfiguration<ObjectProvider> configuration,
> final PerthreadManager perthreadManager
> )
> {
> configuration.add("PerThreadValue", new ObjectProvider() {
> public <T> T provide(Class<T> tClass, AnnotationProvider
> annotationProvider, ObjectLocator objectLocator) {
> return (T)perthreadManager.createValue();
> }
> });
> }
>
> ... but that fails due to the "MasterObjectProvider somehow depends on
> itself" error message and what's probably a blindingly-obvious lack of
> knowledge on my part concerning how tapestry actually provides virtually
> interfaced objects.
>
> So now I have fallen back to patterns like this, that seem to work, but
> seem to be much clunkier than I would expect:
>
> @Inject
> private PerThreadManager perThreadManager;
> private static PerThreadValue<Integer> widgetRenderCount;
>
> void afterRender() {
> if (widgetRenderCount==null) {
> widgetRenderCount=perthreadManager.createValue();
> }
> int count=widgetRenderCount.get(0);
> count++;
> log.debug("{} widgets have now rendered in this request!",
> count);
> widgetRenderCount.set(count);
> }
>
>
> Am I missing something? If so, how is PerThreadValue intended to be used?
>
> --
> Robert Hailey
>
>
>
