asEagerSingleton with factory

Question

I'm very new to Guice, but I have a singleton that I believe would normally be created thusly:

@Provides
@Singleton
private SomeClass getSomeClass()
{
    return someClassFactory(configuration);
}

However, I want this to be eagerly initialized. When I remove the @Singleton annotation and try to bind(SomeClass.class).asEagerSingleton() I get errors:

 1) No implementation for SomeClass was bound.
 2) A binding to SomeClass was already configured

How can I provide an Eagerly initialized singleton that is constructed with parameters or a factory?

Answer 1

The @Provides annotation is a separate way to configure a binding for SomeClass; it's conflicting with the bind(SomeClass.class).asEagerSingleton() binding.

To fix it, you'll need to write an explicit provider class and bind it using toProvider:

class MyModule extends AbstractModule {

  private static class MyProvider implements Provider<SomeClass> {
    private final OtherStuff otherStuff;

    @Inject
    MyProvider(OtherStuff otherStuff) {
      // Inject constructor params if your @Provides method took arguments
      this.otherStuff = otherStuff;
    }

    public SomeClass get() {
      return new SomeClass(otherStuff);
    }
  }

  protected void configure() {
    bind(SomeClass.class).toProvider(MyProvider.class).asEagerSingleton();
  }
}