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Rony,
On 10/13/19 08:40, Rony G. Flatscher (Apache) wrote:
> Chris:
>
> thank you for your information and reflections!
>
>> On 10/10/19 08:16, Rony G. Flatscher (Apache) wrote:
>>
> ... cut ...
>>> Maybe if some standard "script" taglib library for
>>> javax.script languages existed like the proof-of-concept one in
>>> [1] then that could be exploited/(re)used rather than coming up
>>> with non-standard implementations of their own.
>>
>> I hesitate to say this due to your previous experience with tag
>> libraries, but ... a tag library is basically a JSP thing which
>> obviates the need to use any actual Java in the JSP file.
>>
>> (My statements here are basically already covered in the
>> publication; I'm re-itterating them, here for emphasis and
>> clarification.)
>>
>> There isn't anything inherently Java-esque about any of the
>> existing tag libraries (e.g. JSTL), and once you have converted a
>> page filled with spaghetti Java code in scriptlets (e.g. <% java
>> goes here %>) into one that exclusively uses tag libraries, the
>> implications of using <%@page language="java" instead of e.g.
>> language="jython" or whatever kind of evaporate.
>>
>> That is, if you write a tag library, then:
>>
>> 1. Using the taglib in the JSP file isn't using Java 2. Using the
>> taglib in the JSP isn't using the other language, either...
>> instead, it's using ... taglib-lang or whatever you want to call
>> that
>>
>> So if you want to do this:
>>
>> <%@page language="c" import="<stdio.h>" %> <% println("Hello,
>> world!\n"); %>
>>
>> Then you'd need to get a "language" binding in JSP.
>>
>> But instead, if you want to to this:
>>
>> <%@page language="doesntmatter"%> <mytaglib:say>Hello,
>> world!</mytaglib:say>
>
> How (where, what needs to be extended, what needs to be deployed
> how) would this have to be implemented to allow it to work
> generically in all containers for all javax.script engines?
>
>
>> Then you can implement the tag library using any programming
>> language you want, as long as you are able to register it
>> properly with the JSP servlet and have it respond to the calls
>> targeted at the tag library interface(s) you have implemented.
>>
>> IMHO, the BSF taglib is a project that deserved to die. It took
>> all of the horrible possibilities of Java scriptlets in JSPs and
>> made the language pluggable so that you could have garbage
>> spaghetti code in your language of choice packaged inside of a
>> JSP. Good riddance.
>>
>> Resurrecting the capabilities of the BSF taglib is, again IMHO,
>> a waste of effort. That effort would be better spent creating
>> better (or more diverse) tag libraries that don't expose the
>> concept of "scriptlets" to the programmer /at all/.
>
> Concurring! :)
>
> Actually in [1], p. 58, last paragraph ( almost ten years ago) the
> student concluded:
>
> "While the Script Tag Library fills a gap in current Java web
> development technology, more work could be done on the JSP
> specification itself. The specification already includes the page
> directive facility for specifying the language of a JSP page. Now
> that JSR-223 is part of the core Java library, it is possible to
> mandate that implementing containers should support languages other
> than Java by using the javax.script API. While this would prevent
> the mixing of multiple scripting languages on one page, it is
> unlikely that a JSP page would be worked on by multiple developers
> using different scripting languages, making that ability something
> of an edge case."
>
> What would be the starting point, how would you advise to implement
> this such that any javax.script language could be used just by
> denoting its name? (Short of such a possibility the
> "scriptlet"-concept can hardly be circumvented.)
>
> Or with other words, what is needed to allow "<%@page
> language="rexx"%>" ("rexx" being a javax.script.Engine, could be
> "javascript", "jython", "php", "jacl", "jlog", ...), which might
> be the easiest for the script language programmers?
I think your question *does* have an actual answer, but I'm going to
put it off for one more post, because I think this is the better
answer to your question: "It doesn't matter what is needed, because
it's a bad idea and shouldn't be done, anyway."
If you agree that better tag libraries are needed more than
scripting-style code blocks, then why persist in trying to build-out
technology to enable scripting-style code blocks?
If I were king, I'd deprecate the "language" attribute in JSP and
abolish scriptlets *entirely*, making this whole question moot.
You can also resurrect the BSF-style tag library and allow any kind of
scripting in there -- even mixed-language pages! -- that you want,
which I also think is a bad idea.
- -chris
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