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From Carsten Ziegeler <cziege...@apache.org>
Subject Re: [RT] Spring Configuation
Date Thu, 03 Jan 2008 08:47:16 GMT
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.

> 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


-- 
Carsten Ziegeler
cziegeler@apache.org

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