If your application is not exactly as described, but slightly more
complex and you need to map between myAnimal descriptions multiple
times, not just once, you might consider a Mapbinder. It's similar to
your custom provider solution, but eliminates inline if/else code, and
promotes extension by addition in other modules, since all MapBinder
additions to a given type pair are shared.
class Barn {
@Inject Map<String, Animal> animals;
void foo(String name) {
Animal animal = animals.get(name);
...
}
}
import com.google.inject.multibindings.MapBinder;
class MyModule extends AbstractModule {
private void defanimal(MapBinder<String, Animal>m, String name,
Class<? extends Animal> c) {
m.addBinding(name).to(c);
}
public void configure() {
MapBinder<String, Animal> m = MapBinder.newMapBinder(binder(),
String.class, Animal.class);
defanimal(m, "cow", Cow.class);
defanimal(m, "goat", Goat.class);
}
}
Leigh.
On Feb 17, 4:25 pm, Jonathan Dray <[email protected]> wrote:
> Hi,
>
> I'm using Guice for DI in one of my projects.
> I need to choose the right class to inject depending on the value of a
> property read in a properties file.
> Here is a small exemple of what I want to do :
>
> Class myFarm {
> @Inject
> public myFarm(Animal animal) {
> }
>
> }
>
> Now I want that the Animal injected here should be an instance of a
> "Cow" or a "Goat" (which implements the Animal Interface) mapped from
> the property "myAnimal" read in my application property file.
>
> I thought about two solutions :
>
> 1. use a custom provider to get an animal which takes the value of the
> property as a parameter.
> 2. In the configure method of my Guice Module instance, read the
> property and add a binding depending on the value.
>
> Do I have any other alternative with Guice ?
> Which of these method would you chose in that case ?
>
> Thanks for your help.
> Regards,
> Jonathan Dray
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