Grzegorz Kossakowski skrev:
...
I want
to:
a) allow people migrate to new expressions both in Template and
Sitemap smoothly
b) stay 100% back-compatible with old code behaviour while
implementing new ways of expression evaluation and most importantly
Object Model construction
c) avoid confusion about what's new and what's old
This leads us to small but very important question: how we wrap new
expressions? If I'm not wrong, current preference has been to wrap new
expressions in {}, Daniel confirms[1] this view.
My own opinion is that plain {} are ok in sitemap but will not work well
in general. If choose {} as wrapping characters everything put between
this characters will be considered as expression. If you additionally
remember that all strings inside elements are treated as String
templates you may start to be warned. Take a look this[2] file's snippet:
<style type="text/css">
#files { border-collapse: collapse; border-left: dotted black 1px; }
#files td { padding: 0.1em; border-bottom: dotted black 1px; }
.selected { background: #D0D0D0; }
</style>
It's a content of jx template but obviously we don't want
generator/transformer to interpret this CSS declarations as Cocoon
expressions! We would need to escape {} wrapping characters:
<style type="text/css">
#files \{ border-collapse: collapse; border-left: dotted black 1px; \}
#files td \{ padding: 0.1em; border-bottom: dotted black 1px; \}
.selected \{ background: #D0D0D0; \}
</style>
It's ugly, don't you think?
The DefaultStringTemplateParser is actually implementing the escaping
mechanism from atribute value templates in XSLT
(http://www.w3.org/TR/xslt#dt-attribute-value-template. So the example
rather becomes:
<style type="text/css">
#files {{ border-collapse: collapse; border-left: dotted black 1px; }}
#files td {{ padding: 0.1em; border-bottom: dotted black 1px; }}
.selected {{ background: #D0D0D0; }}
</style>
Which IMO is a little bit less ugly than the "\{", "\}" escaping
mechanism. And furthermore you should have most of your CSS in own files
that you include, shouldn't you.
Looking at the parsing code I get the impression that "}}" -> "}" isn't
implemented correctly.
Next choice could be to use ${}. The problem with this characters is
that they are already used in Template and if we don't pick Jexl
language as default it will break current templates not to mention
confusion it would cause. We could come up with %{}, !{} or whatever is
not used yet. Everyone's keyboard has lot of remaining symbols waiting
for use but I wonder if we really want/need new wrappers.
I woulf be OK, with chosing Jexl as default EL and using "${}", but I
prefer "{}".
/Daniel
I'm stuck. Thoughts?
[1] http://marc.info/?l=xml-cocoon-dev&m=118703810504930&w=2
[2]
http://svn.apache.org/repos/asf/cocoon/trunk/blocks/cocoon-forms/cocoon-forms-sample/src/main/resources/COB-INF/forms/file_explorer_template.xml
