[webbeans-dev] Re: Stereotype inheritance proposal

[Pete Muir]

On 21 Nov 2008, at 18:07, Gavin King wrote:

> oops forgot to attach the spec
>
> On Fri, Nov 21, 2008 at 1:05 PM, Gavin King <gavin at hibernate.org>  
> wrote:
>> I've got feedback from a number of people that stereotype inheritance
>> should be supported, and I agree with this feedback.

I can't see a reason not to support it, except that stereotypes are  
already very powerful, so without seeing use cases for which  
stereotype inheritance is considerably simpler, I would say it's a  
nice-to-have only.

>>
>>
>> I think we should just do it in the simplest possible way and say
>> simply that stereotype declarations are transitive, and
>> meta-stereotypes are inherited by the web bean.
>>
>> Therefore:
>>
>> 1. the sets of interceptor binding types are unioned
>> 2. any conflicts between default scope/deployment type defined by a
>> stereotype and its meta-stereotypes must be resolved by explicit
>> declaration on the web bean
>> 3. all restrictions apply cumulatively
>>
>> And I've written this into section 2.7.1.5 of the attached spec  
>> draft.
>>
>> Questions:
>> ========
>>
>> Does anybody think that the default scope/deployment type declared
>> directly by a stereotype should *override* the default
>> scopes/deployment types declared by its meta-stereotypes? This rule
>> makes a lot of sense, but it kinda makes things a little more  
>> complex.
>>
>> For example:
>>
>> @RequestScoped
>> @Stereotype
>> public @interface Foo {}
>>
>> @SessionScoped
>> @Foo
>> @Stereotype
>> public @interface Bar {}
>>
>> Should we force a web bean that declares @Bar to explicitly specify a
>> scope, or is it better to let @SessionScoped on Bar override
>> @RequestScoped on Foo.

I agree, it makes more sense for the stereotype to override the meta- 
stereotype.

>>
>>
>>
>> Another thing I've just noticed, that applies to interceptor bindings
>> inherited by both stereotypes and other interceptor binding types, is
>> that you could potentially have a web bean with multiple "instances"
>> of the same interceptor binding type - the same type, but different
>> member values. I think we should say that this is a
>> DefinitionException.
>>
>> For example:
>>
>> @Transactional(requiresNew=false)
>> @Stereotype
>> public @interface Foo {}
>>
>> @Transactional(requiresNew=true)
>> @Stereotype
>> public @interface Foo {}
>>
>> @Foo @Bar
>> public class X {}
>>
>> Then X has both @Transactional(requiresNew=false) and
>> @Transactional(requiresNew=true).
>>
>>
>> --
>> Gavin King
>> gavin.king at gmail.com
>> http://in.relation.to/Bloggers/Gavin
>> http://hibernate.org
>> http://seamframework.org
>>
>
>
>
> -- 
> Gavin King
> gavin.king at gmail.com
> http://in.relation.to/Bloggers/Gavin
> http://hibernate.org
> http://seamframework.org
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