One thing I've wanted for a long time in Guice is to specify the scope of
the provided value with an annotation.
You can easily mark the scope of the Provider itself being with an
annotation:
@Singleton public class FooProvider implements Provider<Foo> { ... }
And in a Provider method, the scope annotation applies to the resulting
object:
@Provides @Singleton Foo getFoo() { ... }
You can do it in the module, with bind bind as described in Derrick's
message below:
bind(Foo.class).inScope(Scopes.SINGLETON);
bind(Foo.class).toProvider(FooProvider.class);
But you can't mark it in annotations, at least as far as I can tell, unless
you use an @Provides method.
It makes me want something like this:
@Provides(@Singleton) public class FooProvider implements Provider<Foo> {
... }
Leigh.
On Tuesday, January 10, 2012 2:16:49 PM UTC-8, Derrick wrote:
>
> I have investigated this through experimentation. You can control the
> scope of the Provider and/or the object being provided separately.
>
> The following code ensures that a single Provider is created
>
> bind(IConsumer.class).toProvider(ConsumerProvider.class);
>
> bind(ConsumerProvider.class).asEagerSingleton();
>
> While the following code ensures that BOTH the provider and the object
> provided are singletons:
>
>
> bind(IConsumer.class).toProvider(ConsumerProvider.class).asEagerSingleton();
>
>
> While the following code ensures every injection of a provider and
> every such object provided are distinct objects:
>
> bind(IConsumer.class).toProvider(ConsumerProvider.class);
>
> On Jan 9, 6:05 am, Sam Berlin <[email protected]> wrote:
> > The original poster was asking about the Provider itself, not the scope
> of
> > what it provides.
> >
> > sam
> > On Jan 9, 2012 4:45 AM, "unguiculus" <[email protected]>
> wrote:
> >
> >
> >
> >
> >
> >
> >
> > > Sam,
> >
> > > This is not quite correct. @Provides methods create unscoped instances
> > > unless they are annotated with a scope annotation (e. g. @Singleton).
> > > I think the documentation on this could be improved. It should
> > > especially be mentioned that scoping is possible.
> >
> > >http://code.google.com/p/google-guice/wiki/ProvidesMethods
> >
> > > Reinhard
> >
> > > > I think the catch is that toProvider(SomeProvider.class) is an
> unscoped
> > > > provider binding, so each injection of Provider<T> will create a new
> > > > instance of the Provider (I think), so there's no shared state since
> each
> > > > instance is different. @Provides is analogous to
> > > > toProvider(providerInstance), which in turn is analogous to
> > > > bind(..).toInstance(..), all of which act as singletons and need to
> be
> > > > thread-safe.
> >
> > > > sam
> >
> > > --
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