service locator demo

simpleservicelocator.scala

object ServiceLocatorTest extends App {

  trait SimpleServiceLocator {

    import scala.collection.immutable.HashMap
	  
    private var registry = new HashMap[String,Any]()
	  
    def instance[T](implicit manifest: Manifest[T]): Option[T] = {
      for { 
        factory <- registry.get(manifest.toString)
        instance <- Some(factory.asInstanceOf[() => T]()) 
      } yield instance
    }
    protected def register[T](factory: => T)(implicit manifest : Manifest[T]) {
      registry += (manifest.toString -> factory _)
    }
  }  
  
  class EchoService {
    def echo(echo: String): String = {
      echo
    }
  }
  
  trait EchoClient {
    def callEcho(echoMe: String)
  }
  
  //Constructor Style
  class EchoClientConstructor(echoService: EchoService) extends EchoClient {
    def callEcho(echoMe: String){
      println(echoService.echo(echoMe  + " Constructor Style"))
    }
  }
  
  //Property Style
  class EchoClientProperty() extends EchoClient {
    var echoService: EchoService = null
    def callEcho(echoMe: String){
      println(echoService.echo(echoMe  + " Property Style"))
    }
  }
  
  //Service Locator Style
  class EchoClientServiceLocator() extends EchoClient {
    def echoService = EchoModule.instance[EchoService].get
    def callEcho(echoMe: String){
      println(echoService.echo(echoMe + " Service Locator Style" ))
    }
  }
  
  //Def style
  abstract class EchoClientDef() extends EchoClient {
    def echoService: EchoService
    def callEcho(echoMe: String){
      println(echoService.echo(echoMe + " Def Style"))
    }
  }

  
  object EchoModule extends SimpleServiceLocator {   
    register[EchoService] {
      new EchoService
    }
    register[EchoClientConstructor] {
      new EchoClientConstructor(instance[EchoService].get)
    }
    
    register[EchoClientProperty] {
      val client = new EchoClientProperty()
      client.echoService = instance[EchoService].get
      client
    }
    
    register[EchoClientServiceLocator] {
      new EchoClientServiceLocator
    }
    register[EchoClientDef] {
      new EchoClientDef {
        def echoService = instance[EchoService].get
      }
    }
  }
  
  val echoClientA: EchoClient = EchoModule.instance[EchoClientConstructor].get
  val echoClientB: EchoClient = EchoModule.instance[EchoClientProperty].get
  val echoClientC: EchoClient = EchoModule.instance[EchoClientServiceLocator].get
  val echoClientD: EchoClient = EchoModule.instance[EchoClientDef].get
  
  echoClientA.callEcho("echo me")
  echoClientB.callEcho("echo me")
  echoClientC.callEcho("echo me")
  echoClientD.callEcho("echo me")
  
}