Carsten Ziegeler wrote:
Ate Douma schrieb:
Carsten Ziegeler wrote:
Ate Douma wrote:
Carsten Ziegeler wrote:
Ok, I'm back from vacation and thought about this a little bit more. I
think my old proposal (quoted below) is not needed and all we need is
something as Ate proposed: a xml schema extension for spring handling
conditionals.
If noone has done looked into this yet, I'll have a look in the next
days if it's possible.
That would be great!
I haven't had time to further investigate and search for possibly
already defined/discussed similar solutions (the spring forums
especially).
So you're more than welcome to dive into it Carsten :)
I searched a little bit but didn't find similar solutions yet (but I'll
continue searching). In the meantime I looked at the namespace handling
stuff in Spring again, and it seems that's impossible to implement
conditional bean definitions with a namespace. The only working way
would be to wrap each bean definition with a condition, like
<bean name="general-db-service".../>
<cond:if test="o.a.jetspeed.db = hqsldb">
<bean name="...."/>
</cond>
<cond:if test="o.a.jetspeed.db = hqsldb">
<bean name="...."/>
</cond>
<cond:if test="o.a.jetspeed.db = derby">
<bean name="...."/>
</cond>
I looked into the Spring (2.5) custom NamespaceHandler feature this
evening and I think it actually should be possible to wrap a bean
definition, including with its own namespace handling, with a custom
namespace.
In a custom BeanDefinitionParser handling the condition logic you can
"delegate" back parsing a nested bean definition as top level bean using
the passed on ParserContext its BeanDefinitonParserDelegate.
As far as I know, you can wrap exactly one bean definition with one
element. So this rules out, wrapping several bean definitions at once
and it also rules out creating a nice xml syntax (like
<cond:choose><cond:when>...). Wile the second one is not that important
I think the first one is really annoying.
AFAIK both should be possible.
The root level condition element has full control over parsing its own sub
elements (and registering zero or more beans from it).
And for sub elements which don't belong to its own namespace (like a <cond:when> which it can/should handle itself) it can delegate parsing those one by one to
the ParserDelegate, thereby also supporting other namespaces.
I don't have time left tonight to test this out, but I'll do that later
this week or this weekend.
If this works out as I expect, it should be easy to write an EL based
condition namespace bean parser providing just the features we need.
And if this holds true, I prefer to experiment with it from within the
Jetspeed code base itself for now.
Then, once all the features have been fleshed out and tested properly,
we can see if we can promote it to a separate generalized Spring
configuration tool like the Cocoon Spring Configurator, or maybe even
better, contribute it back to Springframework itself if they are
interested.
Yeah, I'm fine with that.
Carsten
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