I have just released static-config which is very small library that allows to scrap some boilerplate when working with typesafehub/config. Here you can find motivation for writing it.

Motivation

I tend to use typesafehub/config pretty extensively and in most cases I use it in similarly way: application.conf in resources + wrapping object for type safe accessing of config entries. Here is small example:

application.conf

my-app {
  app-name = "My Fancy App"
  kafka {
    brokers = ["broker1", "broker2"]
  }
  http {
  interface = "0.0.0.0"
    port = 8080
  }
}

Config.scala

object Config {
  val config = ConfigFactory.load().getConfig("my-app")
  
  val `app-name` = config.getString("app-name")
	
  object kafka {
    val config = Config.config.getConfig("kafka")
    val brokers = config.getStringList("brokers")
  }
	
  object http {
    val config = Config.config.getConfig("http")
    val interface = config.getString("interface")
    val port = config.getInt("port")
  }
}

As you can see, Config code is rather verbose. Every config entry is triplicated(application.conf, name of the variable and argument to the getXY. Moreover, for each entry we need to specify from which config we want to get our entry. That made me think.

static-config

So I developed this tiny library to scrap (almost) all of this boilerplate. I have to mention it wouldn’t be possible without great lihaoyi/sourcecode.

Here is above example written with static-config.

import com.typesafe.config.{Config, ConfigFactory}
import staticconfig._

object SConfigExample extends SConfig {

  override def config: Config = ConfigFactory.load()
  
  object `my-app` extends LocalSConfigNode {
    val `app-name` = configEntry(_.getString)
  
    object kafka extends LocalSConfigNode {
      val brokers = configEntry(_.getStringList)
    }
  
    object http extends LocalSConfigNode {
      val interface = configEntry(_.getString)
      val port = configEntry(_.getInt)
    }
  }
}

No boilerplate left! Success! (In fact we could make ConfigFactory.load() a default implementation of config but that has some drawbacks. Let’s just act like it is not there.)

How it works?

I didn’t lie, this library has only 6 relevant lines of code. If you’re interested go and read it!