Will this make the instance a singleton?

[LoneWolf]

Hi.
Consider this module:
[code]
public class MyModule implements Module {
public void configure(Binder binder) {
// Bind Bar to an instance of Bar.
Bar bar = new Bar();
binder.bind(Bar.class).toInstance(bar);
}
}
[/code]
Does the previous code mean that Bar bar reference will be a singleton
and Guice will inject it into each object has dependency on Bar
object?
Thanks.

[Robbie Vanbrabant]

You could think of this as a singleton. But:
- This rules out constructor injection
- You're bypassing Guice's real scoping mechanism
- Doing work in modules not related to configuration itself is a bad practice.

You should consider using asEagerSingleton or in(Singleton.class) instead.
IMO, the only valid use for toInstance is binding constants (to get some extra help from the compiler)

Robbie

[Sam Berlin]

> You should consider using asEagerSingleton or in(Singleton.class) instead.
> IMO, the only valid use for toInstance is binding constants (to get some
> extra help from the compiler)

Another very good use for toInstance is binding mock objects in tests.
(Especially if Guice is hacked up to support overriding bindings.)

Sam