CODEWITHSUNDEEP
scaladependency-injectionplayframeworkguice
Serendipity
Serendipity

Reputation: 1037

Guice Assisted Inject with Providers or FactoryModuleBuilder

This is kind of a weird use-case and I need some help in figuring out how to use Assisted/Providers/FactoryModuleBuilders in conjunction with each other. Ignore the absence of @Singleton. This is just an example.

A set of traits belonging to a library I cannot change have the following pattern. It uses Cake Pattern.

trait A { //Has abstract methods and abstract service 'webService' }
trait B extends A { //First Concrete Service Implementation assigned to 'webService' }
trait C extends A { //Second Concrete service Implementation assigned to 'webService' }

Since the traits cannot be directly injected, I created a wrapper that would allow them to be injected

BB extends B
CC extends C

In my code, I have a Controller that depends on a Service, that in turn depends on the library. The service should be able to either use "BB" or "CC" depending on what the controller needs. So the components look like the following

I create my service as

//Note: Uses 'trait A' with @Assisted
class SomeWebServiceComponent @Inject()(@Assisted aInstance: A, foo: Foo){
    //Do something with aInstance
}

The Factory to create this (should be created by Guice by using FactoryModuleBuilder)

class SomeServiceFactory {
    def getWebServiceComponent(a:A) SomeWebServiceComponent
}

The FactoryModule will look something like this

class ApplicationModule extends AbstractModule {
  override def configure() = {
    install(new FactoryModuleBuilder().build(classOf[SomeServiceFactory]))
  }
}

I don't mind annotating the controllers with the actual classes that I need.

class OneController @Inject()(factory: SomeServiceFactory, bb: BB) extends Controller {
    val webServiceComponent = factory.getWebServiceComponent(bb)
}

class AnotherController @Inject()(factory: SomeServiceFactory, cc: CC) extends Controller {
    val webServiceComponent = factory.getWebServiceComponent(cc)
}

With this setup, I get errors of the following kind

No implementation for 'A' annotated with @com.google.inject.assistedinject.Assisted(value=) was bound

I need to understand how I can tell Guice that there are two implementations for Trait A, namely, BB and CC and the choice will be supplied at runtime.

Is there a way to achieve this use-case?

Upvotes: 1

Views: 757

Answers (1)

Serendipity
Serendipity

Reputation: 1037

Ok, I created a separate project to test this whole scenario. And it works the way the question is framed.

It turns out, the test cases that I were using, were not currently using GuiceInjection directly. The error message was however, so specifically related to GuiceInjection that I never investigated if the test setup was correct.

Changing the test base, resolved the issue.

Upvotes: 2

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