OK, Dan, I'll have to respect your judgment on this because I'm not up
to date on how this stuff works in JSF2.
So I'm happy to make changes with respect to JSF conversation
propagation rules if it doesn't disrupt/delay the RI team (Pete,
WDYT?) and if there are no objections from the EG (anyone?).
But it seems that you're asking for two changes here:
(1) that the conversation is restored at the beginning of RESTORE_VIEW
(2) that you want some kind of conversation propagation to other servlets
Change (1) seems a pretty straightforward change.
So we get to (2).
Currently we don't even have a built-in conversation context in
servlets and we would need some kind of additional rules surrounding
conversation propagation between servlets. I think what you are
suggesting is that the conversation is propagated whenever there is a
request parameter named "cid" containing the conversation id, and that
it is the user's responsibility to pass it along through the view.
That doesn't sound unreasonable to me at this moment, and is probably
not very difficult to specify.
However, I'm concerned about two things here:
(a) we don't provide a way to propagate conversations by a "natural
id" held in some other request parameter - yes, I know we don't
provide that for JSF either, but in the servlet world it seems even
more important.
(b) impact upon the RI timetable.
Today we can provide a portable extension that does conversation
propagation in servlets, using cid, or natural ids. If we bake
something into the spec, that becomes a little more difficult.
So I want to know that this is *really* something that we should
address in this release.
On Thu, May 28, 2009 at 9:32 PM, Dan Allen <dan.j.allen(a)gmail.com> wrote:
Gavin,
Since you reached an interlude (however brief it may be), I'd like to take
the opportunity to reconsider the conversation context lifecycle. Currently,
the spec states:
- For a JSF faces request, the context is active from the beginning of the
apply request values phase until the response is complete.
- For a JSF non-faces request, the context is active during the render
response phase.
I feel that these boundaries are two narrow. I'll focus first on the faces
request. In Seam, it's necessary to delay resuming the conversation until
the apply request values phase because the conversation id is stored in the
view root. At one time, the conversation context was even stored in the view
root, making it even more imperative. But we get a chance to start fresh.
There are three factors that call for the boundaries to be extended:
- As of JSF 2.0, parts of the component tree is visited in the restore view
phase, which happens to resolve value expressions bound to UIData
components. This triggers a scope not active exception if a
conversation-scoped bean is hit.
- JSF 2.0 gives us far greater flexibility to control inbound and outbound
requests. So it's no longer necessary to store the id in the view root. The
query string would be sufficient (I've already modified Web Beans to
prototype this)
- Servlets on subsequent requests may want to participate in the
conversation (and perhaps even servlet filters)
For all of these reasons, I'd like the conversation lifecycle to wrap the
entire JSF lifecycle and i'd like the conversation id to be propagated using
a query string parameter since that's the most universal way of propagating
state. As a result, custom servlets can read this value and restore the
conversation as needed. It's really inconvenient for the conversation id to
be hidden away into the component tree, aside from being problematic in JSF
2.0.
Please reconsider. Thanks.
-Dan
--
Dan Allen
Senior Software Engineer, Red Hat | Author of Seam in Action
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http://mojavelinux.com/seaminaction
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Gavin King
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