Redirect legacy loggers to slf4j/logback

sbt-logging.scala

import sbt.Keys._
import sbt._

object ApplicationBuild extends Build {

  val unifiedLogging = Seq(
    "commons-logging" % "commons-logging" % "99-empty",
    "log4j" % "log4j" % "99-empty",

    "org.slf4j" % "log4j-over-slf4j" % "1.7.9",
    "org.slf4j" % "jcl-over-slf4j" % "1.7.9",
    "org.slf4j" % "jul-to-slf4j" % "1.7.9"
  )
  
  val appDependencies = libraryDependencies ++= unifiedLogging
  
  val main = Project("your_project", file(".")).settings(
    appDependencies: _*
  ).settings(
    resolvers += "version99" at "http://version99.qos.ch/"
  )
}