[webbeans-dev] Re: Hierarchical Managers

[Gavin King]

I've discovered a problem with setCurrent(scopeType).

What if I called:

   child1.setCurrent(BusinessProcessScoped.class)
   child2.setCurrent(SessionScoped.class)

Then I would have an ambiguity about "which" current manager was
intended, since there is no definable ordering between these to
scopes.

There's two possible solutions to this:

(1) Limit setCurrent() to the request scope, and require that the
orchestration framework take care of propagation to other requests.
(2) Say that if 2 different current contexts have different child
managers defined, an exception is thrown

Which option do you think we should go for?

On Thu, Nov 27, 2008 at 4:30 PM, Gavin King <gavin at hibernate.org> wrote:
> On the concall, we made some significant progress with the design for
> hierarchical Managers. We decided to develop the following approach:
>
> (1) web beans belonging to a child manager may have any scope
> (2) each child manager has its own set of contexts (there is a
> parallel context hierarchy for each scope) that "belong" to, and have
> the same lifecycle as, the parent contexts
> (3) therefore the web beans belonging to the child are not visible to
> web beans belonging to the parent
> (4) however, web beans belonging to the parent *are* visible to web
> beans belonging to the child
> (5) a child manager may be associated with a context by calling
> Manager.setCurrent(ScopeType), and is then automagically propagated
> with the context
> (6) web beans belonging to the child manager may be obtained via EL
> evaluation whenever the child manager is in scope, or by directly
> calling a getInstance() method of the child manager
>
> The needed API changes are as follows:
>
> Manager {
>    public Manager createChild();
>    public void setCurrent(Class<? extends Annotation> scope);
>    public void validate();
> }
>
> Context {
>    getChild(Manager childManager);
> }
>
> There is one question remaining open:
>
> Should it *ever* be possible to access a web bean belonging to the
> child manager via a reference that was injected into a web bean
> belonging to the parent manager or into some non-contextual object
> such as a servlet or MDB?
>
> For example, we might choose to support this in the case that the
> child manager web bean specializes the parent manager web bean.
>
> Bill, is this a feature that Oracle requires? If not, I'm inclined to
> *not* support it in web beans 1.0.
>
> --
> 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