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From Leszek Gawron <lgaw...@mobilebox.pl>
Subject Re: Expression languages (was Re: [RT] StringTemplate: The answer to our templating needs?)
Date Fri, 29 Oct 2004 10:30:57 GMT
Carsten Ziegeler wrote:
> Sylvain Wallez wrote:
> 
> 
>>That's exactly what I suggest above: we choose a standard 
>>default language, but open the possibility to plug in new 
>>ones. XPath is a must-have, Jexl and IM have very valid use 
>>cases which IMO justify them to be provided by Cocoon. Other 
>>languages are just a possibility that we offer _if_ people 
>>want to add their own language.
>>
> 
> What can you do with Jexl what you can't do with an XPath based
> language? My understanding is that they only differ in their syntax
> ('.' instead of '/').
> Now even if Jexl has more functionality I don't see a reason why
> this could not be added to an xpath based language.
> 
> Personally, I like the jexl syntax (with the dots) more, but if 
> we decide to go the '/' way of life, well let's do it - it doesn't
> really matter.
> 
> Carsten
> 
Maybe I do not fully understand JXPath but I had a lot of troubles with 
evaluating expressions that involved java beans and some test conditions 
(equality). I had to convert some of jx:if conditions to Jexl because I 
couldn't make it work for JXPath.

I also see from my experience that Jexl has a much lower learning curve (at 
least for my developers who are familiar with Java and not so much with XPath).

I do not see much space for next language in JX if the language is 
another-bean-or-xml-query-language. What I would really like there is the 
ability to write a little more soplisticated macros. jx:macro simplicity 
causes more sophisticated macros impossible to write. I implemented a reusable 
list control (something like http://valuelist.sourceforge.net/) in JX with 
controls for:
- filtering
- paging (next, prev, first, last, no per page, seek to page number)
- row actions
- list control actions

but it turned out that what I have implemented imposes a lot of constraints on 
how a developer should use it. I see a little space of improvement with 
current jx:macro implementation.

-- 
Leszek Gawron                                      lgawron@mobilebox.pl
Project Manager                                    MobileBox sp. z o.o.
+48 (61) 855 06 67                              http://www.mobilebox.pl
mobile: +48 (501) 720 812                       fax: +48 (61) 853 29 65

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