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From Randy Watler <wat...@wispertel.net>
Subject Re: Adding Required Spring Categories Metadata for Filtering
Date Wed, 18 Feb 2009 16:14:07 GMT
Ate,

Thanks for the reply. I am still pondering this, so I am not sure I am 
going this route. If I do, I will follow your suggestions below.

Would you have any objections to using a separate meta tag key for 
required, (and possibly inverse), categories? I understand the use of a 
'-' and '+' in CSV lists is a pattern in Spring, but unless we start 
writing full predicate expressions, the syntax is going to be obtuse for 
the layman. Do you think something like this is more clear or more 
confusing?

<meta key="j2:requires" value="ojb"/>
<meta key="j2:cat" value="dbPageMangler"/>
<meta key="j2:alias" value"..."/>

In fact, perhaps this is even better:

<meta key="j2:requires" value="ojb"/>
<meta key="j2:supports" value="dbPageMangler"/>
<meta key="j2:alias" value"..."/>

That way I could also support this syntax in parallel:

<meta key="j2:cat" value="dbPageMangler,+ojb"/>
<meta key="j2:alias" value"..."/>

Thoughts?

Randy

Ate Douma wrote:
> Hi Randy,
>
> See inline comments below.
>
> Randy Watler wrote:
>> Gang,
>>
>> I have been pondering how to add a switch type flag to be used to 
>> select cross component technology implementations within the Spring 
>> configurations for J2. I am pondering categories like 'ojb' and 
>> 'jpa'. To be honest, I really am not convinced that filter/categories 
>> is the greatest solution, but I am trying to work with it.
>>
>> The filtering logic seems to be strictly an 'OR' operation. In other 
>> words, if any category defined in the meta data matches the current 
>> category set, the bean is included. Selecting cross concerns like 
>> 'ojb' or 'jpa' might be easier to specify as an 'AND' operation. 
>> Basically, I want to say something like: "use this bean only if a 
>> specific category is defined" in addition to the existing categories 
>> logic.
>>
>> I am doubling down on the complexity for sure, but I am wondering if 
>> this approach would have any objectors? Perhaps it is already 
>> implemented? Just checking first before I go down the path. All 
>> feedback welcome.
> You're assessment is correct: *currently* filtering only works using 
> 'OR' operations.
> Adding 'AND' (and likely '!') operations definitely would be very 
> helpful but so far we haven't had time (nor real need) to add that.
> Doing so probably shouldn't be too difficult to do.
> The current 'OR' handling is handled in the 
> JetspeedBeanDefinitionFilter.match() method, and it simply parses the 
> list of categories specified for a bean and see if any of those match 
> the configured categories.
> Adding 'AND' and '!' logic probably can be add very easily by checking 
> if a specified category starts with a '+' (AND) or '-' (NOT) and then 
> deal with it accordingly.
>
> I surely see no objections to adding such functionality!
>
> Regards,
>
> Ate
>>
>> Randy
>>
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>
>
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