Does scala/typesafe Config offer some way how to configure pluggable implementation of the trait?

Question

I am facing following task of providing implementation of the trait as a configuration option. I have following class hierarchy :

trait Storage {
  def store()
}

object LocalStorage extends Storage {
   def store(){ ... }
}

object RemoteStorage extends Storage {
   def store(){ ... }
}

Having a configuration in property file:

storage.class = "com.xxx.LocalStorage"

Having an implementation on the persistence layer:

class CheckPersister{
val storageType = ConfigFactory.load().getString("storage.class")
val storage: Storage = Class.forName(storageType).asInstanceOf[Storage]
...
}

Is there a better way of dealing with this kind of configuration? I am using Typesafe configuration.

Thx

Answer 1

Directly specifying the name of the class in the config file looks like a bad idea. Would something like this be acceptable instead?

storage.location = "local"

class CheckPersister {
  val storageType = ConfigFactory.load().getString("storage.class")
  val storage: Storage = storageType match {
    case "local" => LocalStorage
    case "remote" => RemoteStorage
    case x => throw new RuntimeException(s"Invalid storage type $x specified")
  }
  ...
}

In this way you can't accidentally instantiate a class you didn't intend.