Scala Load Configuration With PureConfig

In this post, we will discuss a better way of loading the configuration of certain types. Nowadays, we use Typesafe config for the same purpose. PureConfig also uses Typesafe config internally but also provides the better way of doing this.

PureConfig is not a configuration library. It can be seen as a better front-end for existing libraries. It uses the Typesafe Config library for loading raw configurations and then uses the raw configurations to do its magic.

The goal of PureConfig is to create, at compile-time, the boilerplate necessary to load a configuration of a certain type. In other words, you define what to load and PureConfig provides how to load it.

To use the PurConfig, we need to add the dependency in build.sbt for scala 2.11, 2.12:

"com.github.pureconfig" %% "pureconfig" % "0.7.2"

Now define the config in the application.conf file:

company {
    full-name = "Knoldus Software LLP"
    started = 2012
    employees = "80-120"
    offices = ["India", "Singapore", "US", "Canada"]
    offices-in-india {
        head-office = "Delhi"
        development = "Noida"
    }
}

As you can see above, there are different types of values present: List, Map, String, Int.

Now define the Scala types for the config to be converted:

case class Company(company: CompanyDetails)

case class CompanyDetails(fullName: String,
                          started: Int,
                          employees: String,
                          offices: List[String],
                          officesInIndia: Map[String, String],
                          extraActivity: Option[String])

By analyzing the config and the case class, you will notice that field’s name in the config is in Kebab case (full-name), while in the case class it is in camel case (fullName). This is the default behavior. We will see the customized behavior for defining a field’s name in some upcoming posts.

Now load the config:

import pureconfig.error.ConfigReaderFailures
import pureconfig.loadConfig

val simpleConfig: Either[ConfigReaderFailures, Company] = loadConfig[Company]

simpleConfig match {
    case Left(ex) => ex.toList.foreach(println)

    case Right(config) => println(s"Company's Name ${config.company.fullName}")
      println(s"Company started at ${config.company.started}")
      println(s"Company's strength is ${config.company.employees}")
      println(s"Company's presence are in  ${config.company.offices}")
      println(s"Company's office in India are  ${config.company.officesInIndia}")
      println(s"Company's extra activity is  ${config.company.extraActivity}")
  }

That’s it! Hope you enjoyed the read! If you want to explore more, you can get the full code here.

Happy Config'ing!