More importantly, you want those EL expressions evaluated at the
point where they are needed, rather than at page/config load
time.
So the simple example that uses a prompt of the form
<prompt>Hello ${model.user}</prompt>
if placed in a config file would end up getting compiled down to
a prompt
<prompt>Hello ""</prompt> since at the time that that expr gets
compiled, the user has not provided the prompt yet.
The delayed evaluation in
<prompt>hello #{model.user}</prompt>
allows the value populated in the model by a previous dialog
getting spliced into the prompt, which is what you want.
>>>>> "Rahul" == Rahul P Akolkar <[EMAIL PROTECTED]> writes:
Rahul> Stu Robertson <[EMAIL PROTECTED]> wrote on
Rahul> 08/18/2005 12:27:26 AM:
>> Hi,
>>
>> Just reading through the source code I noticed that the
>> ExpandTag accepts bodyContent with #{...} syntax, converts
>> it to ${..} format, and then applies the EL interpreter to
>> it. I haven't noticed this in the docs, and am just
>> curious why the delayed execution is there. Is it so that
>> even cached, otherwise non-dynamic config file contents
>> can be made dynamic when the expand tag is rendered?
Rahul> <snip/>
Rahul>
Rahul> More or less, the expressions do not need to evaluated
Rahul> until certain conditions are met -- i.e. you've
Rahul> reached a particular state in a component or a
Rahul> particular rule within a group's config has been
Rahul> fired. It is also worth noting that the reason the
Rahul> configs exist as separate files is a facet of this RDC
Rahul> implementation, and the configs could well reside
Rahul> within the JSP if someone wants to scratch an itch, in
Rahul> which case, having two notations becomes mostly
Rahul> inevitable.
Rahul>
Rahul> For completion, this is analogous to the EL 2.1 spec
Rahul> draft Section 1.2.4 (component of the JSP 2.1 spec
Rahul> draft):
Rahul>
Rahul> <quote>While ${} and #{} eval-expressions are parsed
Rahul> and evaluated in exactly the same way by the EL, the
Rahul> underlying technology is free to impose restrictions
Rahul> on which syntax can be used according to where the
Rahul> expression appears.</quote>
Rahul>
Rahul> As you note above, the RDC framework uses the #{}
Rahul> notation in the config files (component or group) to
Rahul> stress that those expressions use delayed / deferred
Rahul> evaluation.
Rahul>
Rahul> -Rahul
--
Best Regards,
--raman
------------------------------------------------------------
T. V. Raman: PhD (Cornell University)
IBM Research: Human Language Technologies
Architect: RDC --- Conversational And Multimodal WWW Standards
Phone: 1 (408) 927 2608 T-Line 457-2608
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