Play AutoConfig

AutoConfig is a utility for type-safe configuration in Play (2.6.0 and later). The library provides a convenient macro to generate ConfigLoader instances for arbitrary classes.

Example

For example, suppose I want to read configuration for a hypothetical API I'm making calls to. Let's assume I need an API key, an API password, and I want to configure the request timeout. So I create a class like this:

case class FooApiConfig(
  apiKey: String,
  apiPassword: String,
  requestTimeout: Duration
)
object FooApiConfig {
  implicit val loader: ConfigLoader[FooApiConfig] = AutoConfig.loader
  def fromConfiguration(conf: Configuration) = conf.get[FooApiConfig]("api.foo")
}

The fromConfiguration method shows how you'd use the ConfigLoader using the Configuration#get method. In this case it would read a configuration object that looks like this:

api.foo {
  apiKey = "abcdef"
  apiPassword = "secret"
  requestTimeout = 1 minute
}

The loader macro goes through each parameter of the default constructor and looks for a ConfigLoader in scope for that type, then uses the loader to load the key in the object of the same name. In this case Play already provides loaders for String and Duration. If you had a custom object type nested inside, you could generate a loader in the exact same way.