Just to come back on one of my questions: is injection automatically
performed on the fields and methods of instances bound with
toInstance()?
Thanks for pointing out the MembersInjector. In this case I don't
think I can use it however, for two reasons. Tell me if I'm wrong:
1) My SpyProvider is generic, so I would need to inject a
MembersInjector<T>. Would this work?
2) I instantiate T using its @Inject constructor if present, so I need
to be able to instantiate T's dependencies that appear only in the
constructor parameter list. I don't think these dependencies can be
instantiated with the MembersInjector?
I invite you to look at the code linked with the previous post to see
more details. SpyProvider is a relatively small class.
Cheers,
Philippe
Regarding the MembersInjector, do you suggest replacing this:
public class AbcProvider implements Provider<Abc> {
MembersInjector
On Thu, Nov 4, 2010 at 2:25 AM, Sam Berlin <[email protected]> wrote:
> Yup, Providers are automatically injected too. But, injecting the
> "Injector" is considered bad behavior. A little-known but surprisingly
> useful interface called MembersInjector will better do what you want. You
> can change your Provider to inject a MembersInjector<T> into your Provider
> and then call membersInjector.injectMembers(instance). That way your
> provider is dependent just on the dependencies of T and not on everything in
> the Injector.
>
> sam
>
> On Thu, Nov 4, 2010 at 1:57 AM, PhilBeaudoin <[email protected]>
> wrote:
>>
>> I just did something and was surprised to see it work, so I thought of
>> posting it here to see if I could consistently rely on that behavior.
>>
>> I bind some class to a provider instance as such:
>>
>> bind(klass).toProvider(new SpyProvider(TypeLiteral.get(klass)));
>>
>> I need to have access to the Injector within SpyProvider so I @Inject
>> it in a field:
>>
>> public class SpyProvider<T> implements Provider<T> {
>> �...@inject private Injector injector;
>> ...
>> }
>>
>> What I wanted to do at that point was to first create the injector and
>> then use injector.injectMembers(spyProvider) to fill-in the @Inject
>> field. I thought I needed that extra step since SpyProvider is
>> instantiated via new and should therefore not participate
>> automatically in dependency injection.
>>
>> However, I was surprised to see I could skip the injectMember() step
>> and the injected field would be automatically filled-in by Guice after
>> the call to Guice.createInjector(). Is this behavior expected and
>> documented? Can I rely on it? Does it happen only for providers or is
>> it also applied to toInstance() bindings?
>>
>> If you're curious about the codebase where this come from, it is from
>> the Jukito testing framework. The above lines are from:
>>
>> http://code.google.com/p/jukito/source/browse/src/main/java/org/jukito/TestModule.java#82
>> and
>>
>> http://code.google.com/p/jukito/source/browse/src/main/java/org/jukito/SpyProvider.java
>>
>> Cheers,
>>
>> Philippe
>>
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