To all Tapestry devs,
Please, I want your thoughts before I file a JIRA, just in case I have my
wires crossed.
I'm thinking that Tapestry has real problems working with complex AJAX
pages because there are AJAX components that don't have a context parameter.
The problem I see is that a deeply nested component, C, cannot handle an
event from an AJAX sub-component unless C can reconstruct its context, ie.
C has to be able to restore its parameters. This has been solved in Form
and EventLink by giving them a context parameter. eg.
onPrepareForSubmit(Integer contextArg1) { etc. }
onMyevent(Integer contextArg1) { etc. }
I routinely use this context to restore C's parameters, eg.
@Parameter
private Integer parameter1;
onPrepareForSubmit(Integer parameter1) {
this.parameter1 = parameter1;
}
But what about Select and Grid? Neither of them has a context.
Without a context, C can't handle 2 or more AJAX Select components. When
one sends an event, C has no idea of the value of the other, nor of its own
parameters. A context would fix all of this.
Without a context, an inplace request from a GridPager can't remind C was
currently selected or how the Grid was being filtered. The same goes for
Grid column select events. (See
https://issues.apache.org/jira/browse/TAP5-2297)
There are workarounds, but with a context I think we wouldn't need them:
1. Use @Persist. Well, we all try to avoid this.
2. Include C's parameters in the page's context and make sure they're
passed down through every nested component down to C. But surely that's not
reasonable. What if the page is concerned with a Hospital, but in it our
components drill down through a Ward to a Patient and C is concerned with
the Patient's Diagnosis. Does it really make sense to pass diagnosisId in
through the page context and down through all the in-between components?
Following this logic, we could end up with every parameter of every
component in the page context.
3. Use activation request parameters, but it appears to me to be messy.
@ActivationRequestParameters is only available at the page level, so again
we have to pass them all the way down. Even if we do this, it's a nuisance
to pass them all the way UP in the first place. And again we could end up
with every parameter of every component being declared in the page.
4. Perhaps C can get and set request parameters by hand, but why? Isn't a
context better?
Am I seeing an issue that doesn't exist? Is there a better way?
Cheers,
Geoff
