Hi Eric!
4/ use the @Named annotation via Names.named("xml").
So, is the second approach something like a type safe Named?
> 2/ forces you to change the interface ErrorManager
Why do you need to change the interface?
Regards,
Peter.
On Jan 27, 12:41 pm, eric <[email protected]> wrote:
> Hi,
>
> I'm writting a "small" tutorial for my fellows, and I feel that this
> part was worth sharing with you, to get feedback and discussion on it.
> Thanks.
>
> Dealing with multiplicity in DI.
>
> Multiplicity is always a pain. Unless you have a Singleton
> (manytoOne) , or oneToOne, all the other cases are complicated.
> OneToOne is the default multiplicity for guice. Singleton is easily
> configured in a module.
>
> Though, complicated case are very frequent. Some are design flaw, but
> you can't expect every design to be perfect, and some are not.
>
> For instance, I have "several" ErrorManager"s in my "eclipse-like"
> application, one for each type of editors, and one for general
> purpose.
>
> How to I get the right ErrorManager ?
>
> I'll list all the way I know to deal with it. Not all behave the same,
> all have pro and cons.
>
> 1/ without Guice
>
> Design a singleton service that handles a collection of ErrorManager,
> and then dispatch errors to the appropriate sub ErrorManager.
>
> You'll have to redesign the ErrorManager, so it can take as parameter
> the type of Editor, and redispatch to the appropriate ErrorManager.
>
> In Guice, you have converted a ManytoMany multiplicity into a
> Singleton, and handle the multiplicity by "hand".
>
> 2/ With annotated bindings
>
> You can create an ErrorScope Annotation, that has the Editor Type as
> parameter.
>
> Then in you injectee, you'll do:
>
> @Inject ErrorScope( XMLEditor.TYPE) ErrorManager manager;
>
> An in your Module:
>
> bind(ErrorManager.class).annotatedWith(ErrorScope(XMLEditor.TYPE) ).to
> ( XMLErrorManager.class);
>
> 3/ With private modules
>
> You can inject each Editor within it's own private Module. That means
> it will have access to every bindings, plus the one you defined at
> module level.
>
> Then in you injectee will look like
>
> @Inject ErrorManager manager;
>
> In your main Injector (or in the parent module) :
>
> Injector i = Guice.createInjector( new XMLEditorModule(), new
> JavaEditorModule() , ...)
>
> Where XMLEditorModule extends PrivateModule instead of abstractModule,
> and is configured as follow
>
> bind(ErrorManager.class).to(XMLErrorManager.class);
>
> Is there other ways to handle this example of multiplicity ?
> Which one is the best for you ?
>
> For me, 1/ is an escape line
> 2/ forces you to change the interface ErrorManager and change all the
> code that was using the previous interface.
> 3/ is the best one, but increases the complexity of configuring your
> modules.
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