On Thu, Jan 27, 2011 at 1:04 PM, Nicolas Bouillon <nico...@bouillon.net> wrote:
> Hi,
>
> I would like to share some thoughts about the way the PropertyDisplay works
> (inside the beanDisplay). I choose the PropertyDisplay but it's the same for
> the PropertyEdit.
>
> As we know, we can contribute a BeanBlock to tell tapestry how to display a
> specific datat type. For example I already have overridden the way the date
> is diplayed, or added a BeanBlock for a custom datatype (here for the
> "Decimal" class).
>
> public static void contributeDefaultDataTypeAnalyzer(
> MappedConfiguration<Class, String> configuration) {
>
> configuration.add(Decimal.class, "decimal");
> }
>
> public static void contributeBeanBlockOverrideSource(
> Configuration<BeanBlockContribution> configuration) {
>
> configuration.add(new BeanBlockContribution("date",
> "MyDisplayDateBlock", "date", false));
>
> configuration.add(new BeanBlockContribution("decimal",
> "MyDecimalEditBlock", "decimal", true));
> configuration.add(new BeanBlockContribution("decimal",
> "MyDecimalDisplayBlock", "decimal", false));
>
> }
>
> And the other hand, many times in this mailing list, beginner asks how to
> choose dynamically a component to display on the page. The classic response
> is that it's not possible because the page tree (page and components
> contained in the page) must be known before page execution, Tapestry has
> dynamic behavior but a static structure
> http://tapestry.apache.org/principles.html
>
> But, searching how the BeanDisplay works, I discovered that this component
> cheats and is not so static. To explain rapidly, the BeanDisplay loops on
> each java bean property, and use the PropertyDisplay to display it. The
> PropertyDisplay then use the BeanBlockSource service to lookup how to
> display this property, which finally use the PageCache (an *internal*
> Tapestry service : org.apache.tapestry5.internal.services.RequestPageCache
> ) to dynamically load the page and extracts the Block that will be
> displayed.
Yes, static structure ... but dynamic behavior. Just like the
relationship between Java classes (static structure) and Java
instances (dynamic behavior).
>
> [In org.apache.tapestry5.internal.services.BeanBlockOverrideSourceImpl]
> Page page = pageCache.get(contribution.getPageName());
> return page.getRootElement().getBlock(contribution.getBlockId());
>
>
> My point is :
> 1. The Core Component BeanDisplay, which is sometime presented as a sample
> of what can be done, cannot be realized without using an internal service
> (PagePool), and that is discouraged for upgrade compatibility.
That's just the evolution of the framework; later I added the public
ComponentSource service that can accomplish the same thing, but there
was no pressing reason to recode BeanBlockSource against the new API
when it was fully tested against the old API.
> 2. Dynamic structure is finally possible in Tapestry.
If by finally, you mean "since day 1".
>
> I'm using Tapestry 5 on a daily basis at work. For a dynamic navigation, for
> example, PageRenderLinkSource helped us to check if a specific configuration
> page exists for a product (RuntimeException is thrown on
> createPageRenderLink), and if not then the link we generate directs the user
> to the generic configuration page.
Relying on exceptions is a bit cumbersome; the ComponentClassResolver
service is public and can do a much more efficient job of identifying
which pages exist and which do not.
> Sometimes, I would like to be able to do
> the same for components, but until now, I've already managed to do that in
> an other way, but not always very simple.
>
> It would be nice if the PageCache trick could be possible using a public
> API, because I'm not comfortable using an internal service to reach the
> behavior I would like to have
See notes above.
>
> Any ideas ?
>
> Nicolas.
>
--
Howard M. Lewis Ship
Creator of Apache Tapestry
The source for Tapestry training, mentoring and support. Contact me to
learn how I can get you up and productive in Tapestry fast!
(971) 678-5210
http://howardlewisship.com
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