Stephen McConnell wrote:
> <SNIP EXPLANATION OF MERLIN/>
Thanks Stephen for the info!
> >
> > MyComponent c = (MyComponent)this.serviceManager.lookup(
> > MyService.ROLE + '/' + hint );
> >
> > There is never a lookup that uses some custom role name, like
> > lookup("my-parser"); I think such lookups with custom role names
> > should not be used anyway as they are way too error-prone.
>
> It is only error prone if the lookup key is not scoped to the
> component implementation - for example in any merlin
> component a key is simply a convenience factor local to the
> implementation. The thing I think your getting at is when a
> string is passed to lookup who's semantics are relative to a
> configuration - which means that the component is tied to a
> particular deployment scenario - which is out and out bad.
Yes, exactly.
>
> > And even worse, ECM has the ugly concept of Selectors, so you first
> > lookup a selector using MyService.ROLE+"Selector" and then the
> > component from the selector using the hint. With the following
> > semantics you combine the two in one interface.
> >
> > Now, what do you think of using an easier solution:
> > public interface Locator {
> > Object lookup(Class clazz, String hint); // or Object hint }
>
> I *hate* the "hint" terminology. In English - hint means
> something I can use or ignore. If the string is a key - then
> call it a key - but beyond this - semantics are required.
Agreed: key is a better word (Don't know why the term hint has been
introduced
for this years ago).
> <SNIP/>
>
> Given validation of the above - with complete specification
> of a generic set of semantics of allowable map keys and
> values and the corresponding selection criteria/semantics -
> then you may have a framework candidate.
>
Hmm, I don't think that we have to do it that complicated.
Look at the current contracts of the framework: we have
service manager and service selector which is in combination
a rather ugly approach. So, my suggestion is just to
combine those two in a much nicer way.
Carsten
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