Logger4s is a wrapping SLF4J purely functional library for Scala.
It's easy to use and does not force a specific target context.
You can run your computations in any type F[_].
Logger4s is published to Sonatype OSS and Maven Central:
- Group id / organization: org.pure4s
- Artifact id / name: logger4s
- Latest version is 0.3.1
Usage with SBT, adding a dependency to the latest version of Logger4s to your build.sbt e.g:
// For Scala 2.11, or 2.12
libraryDependencies += "org.pure4s" %% "logger4s-cats" % "0.3.1" // Cats ecosystem (cats-effect)| Module name | Description | Version |
|---|---|---|
logger4s-core |
Algebras. Only if you want to support any backend | 0.3.1 |
logger4s-cats |
Cats ecosystem (cats-effect) | 0.3.1 |
logger4s-scalaz |
Scalaz ecosystem (scalaz-zio) | 0.3.1 |
Example with LazyLogging and Cats:
import cats.effect.IO
import org.pure4s.logger4s.LazyLogging
import org.pure4s.logger4s.cats.Logger
import org.pure4s.logger4s.cats.Logger._
object Main extends App with LazyLogging {
Logger[IO].info(s"Hello word, functional logger").unsafeRunSync()
//2019-03-03 21:34:04.880 [Main$][INFO ] Hello word, purely functional logger
}Example without LazyLogging and Cats:
import cats.effect.{IO, Sync}
import cats.implicits._
import org.pure4s.logger4s.cats.Logger
case class User(email: String)
class UserService[F[_] : Sync : Logger] {
def findByEmail(email: String): F[Option[User]] = {
Logger[F].info(s"User email is $email") *> Option(User(email)).pure[F]
}
}
object Main extends App {
implicit val instance: Logger[IO] = Logger.instance[IO](classOf[UserService[IO]])
val service = new UserService[IO]
service.findByEmail("[email protected]").unsafeRunSync()
//2019-03-03 21:35:35.286 [UserService][INFO ] User email is [email protected]
}Example for comprehensions with LazyLogging and Cats
import cats.effect.{IO, Sync}
import cats.implicits._
import org.pure4s.logger4s.{LazyLogging, Logger}
import org.pure4s.logger4s.Logger._
case class Session(email: String, token: String)
class AuthService[F[_] : Sync] extends LazyLogging {
def login(email: String, password: String): F[Session] = {
def recoveryStrategy: PartialFunction[Throwable, F[Session]] = {
case error =>
Logger[F].error(s"Error creating session", error) *> Sync[F].raiseError(error)
}
val computation = for {
_ <- Logger[F].info(s"Login with email = $email and password = $password")
session <- Session(email, "token").pure[F]
_ <- Logger[F].info(s"Success login with session = $session")
} yield session
computation recoverWith recoveryStrategy
}
}
object Main extends App {
val service = new AuthService[IO]
service.login("[email protected]","123").unsafeRunSync()
//2019-01-27 21:40:40.557 [AuthService][INFO] - Login with email = [email protected] and password = 123
//2019-01-27 21:40:40.557 [AuthService][INFO] - Success login with session = Session([email protected],token)
}Advance example, custom Show with LazyLogging and Cats:
import cats.Show
import cats.effect.{IO, Sync}
import cats.implicits._
import org.json4s.{Formats, NoTypeHints}
import org.json4s.native.Serialization
import org.pure4s.logger4s.{LazyLogging, Logger}
import org.pure4s.logger4s.Logger._
import org.json4s.native.Serialization.write
case class Client(email: String)
object Client {
implicit val formats: Formats = Serialization.formats(NoTypeHints)
implicit val showAsJson = new Show[Client] {
override def show(client: Client): String = write(client)
}
}
class ClientService[F[_] : Sync] extends LazyLogging{
import Client._
def findByEmail(email: String): F[Option[Client]] = {
val client = Client(email)
Logger[F].info(client) *> Option(client).pure[F]
}
}
object Main extends App {
val service = new ClientService[IO]
service.findByEmail("[email protected]").unsafeRunSync()
//2019-01-27 21:25:26.150 [ClientService][INFO] - {"email":"[email protected]"}
}Example with LazyLogging and Scalaz:
import org.pure4s.logger4s.LazyLogging
import scalaz.zio.{IO, RTS}
import org.pure4s.logger4s.scalaz.Logger
object Main extends App with RTS with LazyLogging {
unsafeRun(Logger[IO[Nothing, ?]].info(s"Hello word, purely functional logger"))
//2019-03-03 21:49:59.905 [Main$][INFO ] Hello word, purely functional logger
}People are expected to follow the conduct-code when discussing the project on the available communication channels.
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