Providers work when everything is injected, but in this case, you have a run
time argument. Mixing injected dependencies with run time arguments in a
statically typed-fashion requires you to roll your own factory/builder.
You could just add a predictor setter to DispatchHandler and then just
inject a Provider<DispatchHandler> into Dispatcher, but I prefer things to
be immutable myself.
Bob
On Thu, Oct 16, 2008 at 9:24 AM, Andrew Clegg <[EMAIL PROTECTED]>wrote:
>
> Okay... You took me by surprise a bit, I was expecting something based
> on Provider<DispatchHandler>. Like injecting a
> Provider<DispatchHandler> as one of the arguments to the Dispatcher
> constructor (or a setter).
>
> Have I got the wrong end of the stick? Is that not what Providers are meant
> for?
>
> Thanks,
>
> Andrew.
>
> 2008/10/16 Bob Lee <[EMAIL PROTECTED]>:
> > Oh, Jesse also has AssistedInject which can help with this stuff, but I
> > still like to kick it old school. He can tell you more.
> >
> > Bob
> >
> > On Thu, Oct 16, 2008 at 9:16 AM, Bob Lee <[EMAIL PROTECTED]> wrote:
> >>
> >> Assuming you need to inject stuff into DispatchHandler and you don't
> want
> >> Dispatcher to know about DispatchHandler's deps, here's how I would do
> it.
> >>
> >> public class Dispatcher {
> >>
> >> private final DispatchHandler.Factory handlerFactory;
> >>
> >> // package-private for unit testing
> >> @Inject Dispatcher(DispatchHandler.Factory handlerFactory) {
> >> this.handlerFactory = handlerFactory;
> >> }
> >>
> >> ...
> >>
> >> public boolean dispatch() {
> >> for(PredictorProfile predictor : predictors) {
> >> handlerFactory.newInstance(predictor).start();
> >> }
> >> return true;
> >> }
> >> }
> >>
> >> public class DispatchHandler extends Thread {
> >>
> >> private DispatchHandler(PredictorProfile predictor, Dep1 d1, ...) {
> ...
> >> }
> >>
> >> ...
> >>
> >> public static class Factory {
> >>
> >> private final Dep1 d1;
> >> ...
> >>
> >> // package-private so we can unit test easily.
> >> @Inject Factory(Dep1 d1, ...) { ... }
> >>
> >> ...
> >>
> >> public DispatchHandler newInstance(PredictorProfile predictor) {
> >> return new DispatchHandler(predictor, d1, ...);
> >> }
> >> }
> >> }
> >>
> >> You could also use "Builder" instead of "Factory" depending on how you
> >> structure things. Needing this additional class is unfortunate but
> necessary
> >> unless we extend the language to better support this stuff.
> >>
> >> Bob
> >>
> >> On Thu, Oct 16, 2008 at 9:02 AM, Andrew Clegg <[EMAIL PROTECTED]>
> >> wrote:
> >>>
> >>> Hey folks,
> >>>
> >>> I'm just getting started with Guice (and DI in general). I have a
> >>> question, hope it's not too dense.
> >>>
> >>> I have a method that looks something like this in its first
> >>> incarnation (_predictors is a collection):
> >>>
> >>> public boolean dispatch()
> >>> {
> >>> for( PredictorProfile predictor : _predictors )
> >>> {
> >>> Thread handler = new DispatchHandler( predictor );
> >>> handler.run();
> >>> }
> >>> return true;
> >>> }
> >>>
> >>> i.e. for each predictor that the object knows about, kick off a thread
> >>> to process it, and then return. (The return true is just a placeholder
> >>> for a proper status code later.)
> >>>
> >>> Now I've started to think Guicily, I don't like the look of that call
> >>> to new. Everything else in this app so far is injected for me by
> >>> Guice.
> >>>
> >>> What's the best pattern for this kind of situation?
> >>>
> >>> Thanks!
> >>>
> >>> Andrew.
> >>>
> >>>
> >>
> >
> >
> > >
> >
>
> >
>
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