Exploring DI options

FPStyleDIDemo.scala

package demos

import org.specs2.mutable._

class FPStyleDIDemo extends Specification {

  class Db {
    def name = "sony-db"
  }
  object Db {
    implicit def New = new Db
  }
  //////////
  class Collection(implicit db: Db) {
    def name = s"collection in ${db.name}"
  }
  object Collection {
    implicit def New(implicit d: Db) = new Collection
  }
  //////////
  class Service(implicit collection: Collection) {
    def name = s"service of ${collection.name}"
  }
  object Service {
    implicit def New(implicit c: Collection) = new Service
  }
  //////////
  class Controller(implicit service: Service) {
    def name = s"controller with ${service.name}"
  }

  "DI" should {
    "autowire" in {
      val controller = new Controller
      controller.name mustEqual("controller with service of collection in sony-db")
    }

    "autowire root level changes" in {
      implicit val stubDb = new Db {
        override def name = "stub-db"
      }

      val controller = new Controller
      controller.name mustEqual("controller with service of collection in stub-db")
    }
  }
}

GuiceStyleDIDemo.scala

package demos

import org.specs2.mutable._
import com.google.inject.{AbstractModule, Guice, Inject, Singleton}

@Singleton
class Db {
  def name = "sony-db"
}

@Singleton
class Collection @Inject()(db: Db) {
  def name = s"collection in ${db.name}"
}

@Singleton
class Service @Inject()(collection: Collection) {
  def name = s"service of ${collection.name}"
}

@Singleton
class Controller @Inject()(service: Service) {
  def name = s"controller with ${service.name}"
}

class StubDb extends Db {
  override def name = "stub-db"
}

class GuiceStyleDIDemo extends Specification {

  "DI" should {
    "autowire" in {
      val Injector = Guice.createInjector()
      val controller = Injector.getInstance(classOf[Controller])
      controller.name mustEqual("controller with service of collection in sony-db")
    }

    "autowire root level changes" in {

      val mod = new AbstractModule {
        def configure() {
          bind(classOf[Db]).to(classOf[StubDb])
        }
      }
      val Injector = Guice.createInjector(mod)

      val controller = Injector.getInstance(classOf[Controller])
      controller.name mustEqual("controller with service of collection in stub-db")
    }
  }
}

OOStyleDIDemo.scala

package demos

import org.specs2.mutable._

class OOStyleDIDemo extends Specification {

  trait DbComp {
    class Db {
      def name = "sony-db"
    }
    val db = new Db
  }
  //////////
  trait CollectionComp extends DbComp {
    class Collection {
      def name = s"collection in ${db.name}"
    }
    val collection = new Collection
  }
  //////////
  trait ServiceComp extends CollectionComp {
    class Service {
      def name = s"service of ${collection.name}"
    }
    val service = new Service
  }
  //////////
  class Controller extends ServiceComp {
    def name = s"controller with ${service.name}"
  }

  "DI" should {
    "autowire" in {
      val controller = new Controller
      controller.name mustEqual("controller with service of collection in sony-db")
    }

    "autowire root level changes" in {
      trait StubDbComp extends DbComp {
        override val db = new Db {
          override def name = "stub-db"
        }
      }
      val controller = new Controller with StubDbComp
      controller.name mustEqual("controller with service of collection in stub-db")
    }
  }
}