Hi Scott
Congratulations, both on your wedding and on a great piece of development
work!
> I have been lurking on this list for quite a while now and want to say
that
> I am very impressed with the work you all have been doing. I recently put
> some work into an expression language and associated tag library that I
> would like to donate to this group, if you are interested. The tag
library
> is designed to promote good MVC design, and borrows many usage patterns
from
> XSLT and XPath, but uses Java introspection instead of paths for resolving
> expressions, and errs on the side of Java where things like naming
> conventions are concerned.
>
> More information and examples are at:
>
> http://plaza.isthmusgroup.net/exptags/intro.jsp
This is really cool!
Its very similar to the XTags library in semantics, the XPath-like
expression language, the similar XSLT style tags <forEach>, <valueOf>, <if>
<choose><when><otherwise> <variable> etc. XTags works on XML data, your
library works on Java objects. So they both compliment each other really
nicely. (I'm looking forward to using them both together ;-).
Just a thought, how about calling it JTags? Then we'd have XTags for working
with XML and JTags for working with Java objects (& beans, arrays,
Collections, Maps etc). Nice similarity there?
Also seperating out the expression language from the tag library might be
useful too - certainly Struts may find it useful, I'm sure other projects
will as well. Maybe jakarta-commons might be a good place for the expression
language code to live then it could be used in various (Jakarta &
non-Jakarta) projects - maybe Velocity / Anakia too? I can imagine it being
useful in tools as well such as IDEs, debuggers etc.
Finally a couple of comments about your expression language...
* I'd prefer it if you used the "/" character for the path seperator rather
than ".".
Sure "." is more Java like for Java programmers. Though the people editing
the JSP pages will probably be more XML / HTML / XSLT programmers than Java
programmers, so making the expression language more like XPath would make
more sense IMHO. It would also make JTags and XTags more alike ;-)
Also "." is used to avoid name clashes in page/request/session/application
scope attrbutes lot - often class names or packages are used as attribute
names.
So being able to do something like
$com.acme.model.Customer/name
to lookup a customer variable and get its name property would be valid and
not require any escaping of the "." character.
* Relative / absolute paths and variables.
One neat feature of XPath and XTags / XSLT is that by default path
expressions are relative. So you can do things like...
<xtags:forEach select="order">
<!-- context is now an order -->
order's id is:
<xtags:valueOf select="id"/>
<xtags:forEach select="item">
<!-- context is now an item -->
product name is:
<xtags:valueOf select="product/name"/>
</xtags:forEach>
</xtags:forEach>
In the above, the two <forEach> tags are relative to the 'current context'
like in XSLT / XPath. So nested <forEach> tags can be used to efficiently
navigate down a complex tree structure. So in XPath you can be relative
name = name element of current context
/name = name element of root context
$name = name variable
I don't yet see how this kind of relative navigation and lookup of variables
can be done in your expression language. i.e. how to specify the difference
between
<xtags:forEach select="order">
relative customer for current order
<xtags:valueOf select="customer"/>
variable customer...
<xtags:valueOf select="$customer"/>
</xtags:forEach>
Though the scope axis might have something to do with it? Would your
expression language be something like this?
<jtags:forEach select="order">
relative customer for current order
<jtags:valueOf select="customer"/>
variable customer...
<jtags:valueOf select="page:customer"/>
</jtags:forEach>
> Are you interested in incorporating this tag library?
+1
Yes! This is really cool.
James
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