scoped contexts example

[tom.baeyens]

moving mail discussion to forum:

On Wed, 2007-03-21 at 12:42 +0100, Ales Justin wrote:
> > If you could direct me to your (IoC) work, use cases, ... I will have a
> > look to see more precisely what you may need. And we can discuss this
> > further (at J1, ...).

Tom wants the scoped kernels so he can setup factories at different
levels (in particular "runtime scopes" for his jbpm processes).

e.g. Not Tom's exact example, but probably more familiar to
you from a JavaEE/Seam point of view (note the runtime scopes
web session and seam conversation).

"Application Scope"
DataSource - default for the application

"Web Session Scope"
DataSource -> *override* for the session

"Seam Conversation Scope"
DataSource -> *override* for the conversation

There's a bit more too it than what I describe, but
this is the basic mechanism to the solution.

If you want to discuss this further with me, I'll be
happy to do it in the forums.
-- xxxxxxxxxxxxxxxxxxxxxxxxxxxx Adrian Brock Chief Scientist JBoss, a division of Red Hat xxxxxxxxxxxxxxxxxxxxxxxxxxxx

actually, i have now an implementation with scopes that i'm pretty much satisfied with.

Adrian, this might be interesting for you to have a look at before you start implementing/adding the real thing in the MC.

it's in module lightning of jbpm cvs repo.

src/org/jbpm/ctx --> context and scopes
src/org/jbpm/wire --> wiring

regards, tom.

[adrian.brock]

Adrian, this might be interesting for you to have a look at before you start implementing/adding the real thing in the MC.

It's already being implemented in the MC, but I've already expressed
concerns that it is being done without reference to the use cases. :-)
http://www.jboss.com/index.html?module=bb&op=viewtopic&t=102686

The other parts of your requirement (passing scopes under the wire)
was done last year, although it is still a very internal/mechanistic api
that needs some helpers/wrappers to make it look pretty. :-)

e.g. Your create a bean from the scoped information:

"Helper".createBean("name");

would translated into something like:

// Get the scoped metadata attached to the thread
MetaData scopedMetaData = MetaDataStack.peek();

// Get the scoped controller
KernelController controller = scopedMetaData.getMetaData(KernelController.class);

// Get the factory for the bean from this scope
BeanFactory factory = controller.getInstalledContext("name").getTarget();

// Create the bean (do all the inject wiring in the current scope, etc.
return factory.create()

or alternatively you can do more work yourself, e.g.

// Get the scoped metadata attached to the thread
MetaData scopedMetaData = MetaDataStack.peek();

// Get the wiring implementation for this context
MyWiring wiring = scopedMetaData.getMetaData(MyWiring.class);

// Do any custom wiring based on the controller and scoped metadata
KernelController controller = scopedMetaData.getMetaData(KernelController.class);
return wiring.createBean(controller, scopedMetaData);

[adrian.brock]

On the first example, you don't have to use an MC BeanFactory.

You can use anything that implements BeanMetaDataFactory to express
its dependencies (i.e. what it wants to be injected).