Deferred binding to instance using Guice

Question

I have this in my module:

@Override
protected void configure() {
    bind(Authenticator.class).toInstance(KerberosAuthenticator.create());
}

And the reason for binding to instance here is because Kerberos authentication needs a bit of initialization like so:

    public static KerberosAuthenticator create() {
    KerberosAuthenticator auth = new KerberosAuthenticator();
    auth.start();
    return auth;
}

This works. I particularly like the fact that it works without noise like factories and providers... Can I somehow defer creating this instance. Obviously the create() method is called at the time I am configuring the binding. In this case the creation is not expensive, but in other cases it may be, or, perhaps, not even needed... I am, somehow, missing it in the Guice docs... Thank you.

score 1 · Accepted Answer · answered Apr 25 '19 at 16:30

1

use Provider,

bind(Authenticator.class) .toProvider(AuthenticatorProvider.class)

check this

https://github.com/google/guice/wiki/ProviderBindings

answered Apr 25 '19 at 16:30

hunter

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Hm, I missed it?... I guess I missed it... This is the answer. Makes it very clean at the point of injection. Thank you very much! – AlexeiOst Apr 25 '19 at 16:58

Olivier Grégoire · Answer 2 · 2019-04-26T00:01:49.757

0

You could simply write a provider method:

@Provides
Authenticator provideAuthenticator() {
  KerberosAuthenticator auth = new KerberosAuthenticator();
  auth.start();
  return auth;
}

This meets your requirement of lazyness because (from the page):

Whenever the injector needs an instance of that type, it will invoke the method.

edited Apr 26 '19 at 00:01

answered Apr 25 '19 at 20:31

Olivier Grégoire

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@Provides is not same as Provider. This is not the right answer. – KitKarson Apr 25 '19 at 23:45
@KitKarson It's as good as the other answer. See https://github.com/google/guice/wiki/ProvidesMethods – Olivier Grégoire Apr 25 '19 at 23:50
I saw that already. The OP looks for lazy injection. `@Provides` does not do that. Provider is the right way to do it. `@Provides` would be helpful when you need to do something with the object before injection. But it is not lazy. – KitKarson Apr 25 '19 at 23:57
@KitKarson The documentation I linked states: "Whenever the injector needs an instance of that type, it will invoke the method." That's the definition of "lazy" – Olivier Grégoire Apr 25 '19 at 23:59

Deferred binding to instance using Guice

2 Answers2