This may not really be the best place to raise this question, but it's
related to tag development and may affect the way tags should be designed.
The JSP (1.2 PFD2) spec calls for AT_BEGIN and AT_END to provide for
availability of scripting variables from the appropriate point "until the
end of the page."
I don't see any way of accomplishing that without also making the
variables accessible earlier on the page as well. A scripting-variable
declaration approximately adjacent to the calls to doStartTag() and
doEndTag() -- which is where Jasper locates the declaration in the last
version I checked -- might be contained within a Java '{ ... }' block as
the result either of a scriptlet or of a block that the translator adds
because of a stack of tags. Thus, the declaration would have only the
narrow lexical "block" scope necessitated by the Java language, and it
would not be available outside the containing block.
To make it concrete... In the version of Jasper I tested with (with
Tomcat 4.0 b3), if <x:a> produces an AT_BEGIN scripting variable called
'status', it will not be accessible when it's used in the following
example:
<x:b>
<x:a/>
</x:b>
<%= status %>
That may just be a bug in Jasper, or it may follow the intent of the spec.
(I'm not sure -- I can't find anything in the spec that specifically
supports or refutes this example, other than the language that describes
AT_BEGIN as making a scripting variable available "until the end of the
page." This makes me thing it's a bug.)
If this is a bug, though, then the problem is that any fix would require
the translator to declare a variable before any sub-block present on the
page, and this would make scripting variables available too early. (The
spec doesn't seem to rule that out -- i.e., maybe there's no such thing as
"too early" -- but I could be wrong.)
Does anyone know how other container handle similar situations? Any other
thoughts? I might just be missing something obvious.
Shawn
