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Yet another Typesafe config Scala wrapper powered by circe


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Small library for translating between HOCON, Java properties, and JSON documents and circe's JSON AST.

At a high-level it can be used as a circe powered front-end for the Typesafe config library to enable boilerplate free loading of settings into Scala types. More generally it provides parsers and printers for interoperating with Typesafe config's JSON AST.


To use this library configure your sbt project with the following line:

libraryDependencies += "io.circe" %% "circe-config" % "0.8.0"



The following examples use io.circe:circe-generic as a dependency to automatically derive decoders. They load the configuration found in application.conf.

scala> import com.typesafe.config.{ ConfigFactory, ConfigMemorySize }
scala> import io.circe.generic.auto._
scala> import io.circe.config.syntax._
scala> import scala.concurrent.duration.FiniteDuration

scala> case class ServerSettings(host: String, port: Int, timeout: FiniteDuration, maxUpload: ConfigMemorySize)
scala> case class HttpSettings(server: ServerSettings, version: Option[Double])
scala> case class AppSettings(http: HttpSettings)

// Load default configuration and decode instances
scala> import io.circe.config.parser

scala> parser.decode[AppSettings]()
res0: Either[io.circe.Error,AppSettings] = Right(AppSettings(HttpSettings(ServerSettings(localhost,8080,5 seconds,ConfigMemorySize(5242880)),Some(1.1))))

scala> parser.decodePath[ServerSettings]("http.server")
res1: Either[io.circe.Error,ServerSettings] = Right(ServerSettings(localhost,8080,5 seconds,ConfigMemorySize(5242880)))

scala> val config = ConfigFactory.load()

// Decode instances from an already loaded configuration

scala> config.as[ServerSettings]("http.server")
res2: Either[io.circe.Error,ServerSettings] = Right(ServerSettings(localhost,8080,5 seconds,ConfigMemorySize(5242880)))

scala> config.as[HttpSettings]("http")
res3: Either[io.circe.Error,HttpSettings] = Right(HttpSettings(ServerSettings(localhost,8080,5 seconds,ConfigMemorySize(5242880)),Some(1.1)))

scala> config.as[AppSettings]
res4: Either[io.circe.Error,AppSettings] = Right(AppSettings(HttpSettings(ServerSettings(localhost,8080,5 seconds,ConfigMemorySize(5242880)),Some(1.1))))

If you are using cats.effect.IO, or some other type F[_] that provides a cats.ApplicativeError, you can use the following:

scala> import cats.effect.unsafe.implicits.global
scala> import cats.effect.IO
scala> import io.circe.generic.auto._
scala> import io.circe.config.parser

scala> case class ServerSettings(host: String, port: Int)
scala> case class HttpSettings(server: ServerSettings, version: Option[Double])
scala> case class AppSettings(http: HttpSettings)

scala> parser.decodeF[IO, AppSettings]()
res0: cats.effect.IO[AppSettings] = IO(AppSettings(HttpSettings(ServerSettings(localhost,8080),Some(1.1))))

scala> val settings: IO[AppSettings] = parser.decodeF[IO, AppSettings]()
scala> settings.unsafeRunSync()
res1: AppSettings = AppSettings(HttpSettings(ServerSettings(localhost,8080),Some(1.1)))

scala> parser.decodePathF[IO, ServerSettings]("http.server")
res2: cats.effect.IO[ServerSettings] = IO(ServerSettings(localhost,8080))

scala> parser.decodePathF[IO, ServerSettings]("path.not.found").attempt.unsafeRunSync()
res3: Either[Throwable,ServerSettings] = Left(io.circe.ParsingFailure: Path not found in config)

This makes the configuration directly available in your F[_], such as cats.effect.IO, which handles any errors.


Contributions are very welcome. Please see instructions on how to create issues and submit patches.


To release version x.y.z run:

> sbt -Dproject.version=x.y.z release


circe-config is licensed under the Apache License, Version 2.0 (the "License"); you may not use this software except in compliance with the License.

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.