shale-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Craig McClanahan" <craig...@apache.org>
Subject Re: [dialog] Progress on weekend experiments
Date Fri, 01 Sep 2006 05:19:45 GMT
On 8/31/06, Sean Schofield <sean.schofield@gmail.com> wrote:
>
> @Craig,
>
> Two questions regarding your initial check in ...
>
> 1.) Why doesn't the navigation handler call render response after
> setting the view?  Is that something that is frowned upon?  I noticed
> the myfaces implementation does this (perhaps incorrectly.)


Doing this would be redundant in the normal case, because the navigation
handler is called during Invoke Application phase, so the next phase is
going to be Render Response anyway.  The possible exception is if you set
immediate="true" on the command component that submitted the form ... but
the default ActionListener that calls your action method (and then invokes
the navigation handler) is supposed to have already called renderResponse
before it returns.

It wouldn't hurt anything to call it, though, as paranoid protection against
potential JSF implementation bugs.


2.) Why does LegacyContext need a reference to Contexts?  Its
> currently not being used.   No big deal - I know its the sandbox - but
> did you have something in mind for this reference?


In other conversations on the topic, it seems like some event broadcasting
might allow the  application to specialize its behavior based on what is
going on ... and it would likely be more convenient for the application to
register its event listeners on the session-scoped LegacyContexts object,
rather than the request scoped LegacyContext object where the reference
comes and goes each request (although it is indeed the same instance.  Also,
this would allow us to move the "exit from a dialog programmatically" logic
from the remove() method on LegacyContexts to some sort of close() method on
LegacyContext ... which might be better usability.


Off to create a few test dialogs.  I will report back shortly.
>
> Sean


Craig



On 8/31/06, Sean Schofield <sean.schofield@gmail.com> wrote:
> > On 8/28/06, Craig McClanahan <craigmcc@apache.org> wrote:
> > > I've checked in some progress on my experiments with how we can
> improve the
> > > Dialog functionality.  Even though they're not done yet, they are far
> enough
> > > along to want some feedback and to make them available for
> experimentation
> > > and further development.  This mail will serve as a record of my
> thinking so
> > > far, so you can get a feel for why I took the approach I've taken so
> far.
> >
> > Great.  I think we should do more of this sandbox in progress type
> > stuff.  Its easier to contribute your own ideas if the other person
> > hasn't nailed everything down yet.
> >
> > > Initially, I wanted to address two shortcomings and one expanded
> feature in
> > > our current approach:
> > >
> > > * Make it possible for a single user to have multiple active dialog
> > > instances
> > >   (although limited to one per JSF view, per our discussion).
> >
> > Great.  I see this also handles the "aborted" dialog case (user closes
> > popup window.)  Nicely done.
> >
> > > * Make it possible to programmatically start up a dialog instance, as
> well
> > > as
> > >   start one with a prefix on a logical outcome.
> >
> > This will be real nice.  I see how the create method establishes a
> > context but will this work in a popup scenario?  User clicks on a
> > "Start dialog" link and the dialog starts in a new popup window.  I'm
> > thinking one could use a view controller for your pop up window and
> > call the necessary create method.  Does the programmer need to find
> > the first page of the dialog on their own in this instance?
> >
> > > * Make it possible to plug in different state machine implementations
> > >   (i.e. Commons SCXML), perhaps with different detailed feature sets.
> >
> > I nice to have bonus.
> >
> > > I have *not* tried to address synchronizing state when the user
> presses the
> > > browser navigation buttons yet.  One can of worms at a time
> :-).  Rahul had
> > > some comments earlier today on how SWF deals with this.  Seam does
> something
> > > similar, and we'll undoubtedly need to add functionality here later.
> >
> > Don't worry.  We're not going to solve this anytime soon.
> >
> > > To address these initial concerns, I focused first on abstracting out
> the
> > > APIs that an application *using* the dialog feature should have to
> interact
> > > with, and then providing generic integration for the navigation
> handler that
> > > can start a new dialog, or operate an existing one.  The guts of
> actually
> > > processing the transitions, then, is delegated to a
> state-machine-specific
> > > implementation.  The key APIs are (so far) incredibly simple -- they
> are in
> > > the "shale-dialog2" module in the sandbox.  There are two fundamental
> > > interfaces:
> > >
> > > org.apache.shale.dialog2.Context:
> > >
> > > * Represents the current state of an active dialog instance (similar
> to
> > > Status in the current implementation)
> > >
> > > * One instance per active dialog, rather than one per user
> > >
> > > * Cached in a o.a.s.dialog2.Contexts object stored in session scope
> (see
> > > below)
> > >   in between requests
> > >
> > > * Generic phase listener (o.a.s.dialog2.faces.Dialog2PhaseListener) is
> > > responsible
> > >   for saving and restoring access to the right instance:
> > >
> > >   - Before render response, caches the identifier of the currently
> ative
> > > instance
> > >     (if any) in the JSF component tree, as a generic attribute of the
> view
> > > root.
> > >
> > >   - After restore view, pulls the dialog identifier out, grabs the
> cached
> > > Context
> > >     instance from the session scope Contexts object, and exposes it as
> a
> > > request
> > >     scope attribute under a well known key ("dialog2" for the moment).
> > >
> > > * As we did in the original impl, Context exposes a "data" property
> for the
> > > app to
> > >   store whatever it wants.  So, binding expressions work very
> similarly to
> > > what they
> > >   did before ("#{dialog2.data.name}"), but with the bugfix that it is
> one
> > > instance per view
> > >   instead of one instance per user.
> > >
> > > * Contains an advance() method that can be called to have the state
> machine
> > > work its
> > >   way through the transitions until it runs into a state that needs
> input
> > > from the user (in
> > >   the terminology of the existing impl, that means when you hit a view
> > > state).  The advance
> > >   method returns the view id of the page to display, and a generic
> > > navigation handler
> > >   implementation (o.a.s.dialog2.faces.Dialog2NavigationHandler) then
> does
> > > the actual
> > >   JSF navigation.  NOTE - this navigation handler is generally the
> only code
> > > that should
> > >   call this method.
> >
> > Context stuff looks good.  I'm going to try creating a few dialogs
> > later tonight to actually test it out.  Maybe even add some test
> > cases.
> >
> > > org.apache.shale.dialog2.Contexts:
> >
> > The name confuses me.  I would prefer to call it ContextManager or
> > something like that.  IMO its too confusing (visually) to have Context
> > and Contexts.  They are too similar looking and I find myself stopping
> > and saying "Now which one is it again?"
> >
> > > * Defined by a particular implementation as a session scoped managed
> bean
> > > that is
> > >   stored under a well known key.
> > >
> > > * Maintains a cache of Context instances for the current user, keyed
> by
> > > dialog identifiers,
> > >   so we get the one-per-view capability.
> > >
> > > * Includes a create() method so that you can programmatically start a
> dialog
> > > instance.
> >
> > The functionality of this class looks good.  Just don't like the name.
> >  Is it just me or does the code look a lot cleaner with this
> > refactoring?  It seems easier to follow this way.
> >
> > > The remaining classes in shale-dialog2 implement the JSF integration
> > > (navigation handler and phase listener), and should not be utilized
> directly
> > > by applications.
> >
> > Makes sense.
> >
> > > To validate this design, I've refactored the current support into a
> module
> > > (shale-dialog2-legacy) that does pretty much the same thing as the
> existing
> > > implementation, but organzied with the new APIs.  (Side note ... Sean
> is
> > > definitely not going to like what I did to the config classes, making
> > > everything I could package private ... that's my new habit when
> designing
> > > APIs ... we can make things more public later as needed, but cannot
> really
> > > go the other way.)  As I mentioned in the commit comments, this stuff
> has
> > > only been desk checked and not actually used yet, so it undoubtedly
> has
> > > bugs, but it should be easy to make functional -- and it benefits from
> the
> > > "dialog instance per view" fix in the underlying architecture to fix
> that
> > > problem.
> >
> > I fixed a DTD issue in your faces-config.xml that my IDE was
> > complaining about.  I will put it to an actual test later today.
> > Don't worry about the private vs. public business.  If we take care of
> > the major problems there will be no need to subclass anymore.
> >
> > > A corresponding module for Commons SCXML has been started, but I got
> > > sidetracked a bit on the legacy one.  It'll be pretty easy to finish
> this
> > > off in a similar fashion, though ... that'll be my next step unless
> someone
> > > wants to volunteer to beat me to it.
> >
> > I see Rahul has volunteered for this.  Better him then me ;-)  I think
> > we should ship 1.0.4 with the "legacy" implementation and ship SCXML
> > when its ready.  Also, I think we should change everything from dialog
> > to dialog2, etc. once we move out of the sandbox.  I'm assuming this
> > "2" and "legacy" stuff is just to keep us from getting confused until
> > then?
> >
> > Nice work.
> >
> > > Craig
> >
> > Sean
> > >
> >
>

Mime
  • Unnamed multipart/alternative (inline, None, 0 bytes)
View raw message