By default, Scalatra uses Logback for logging.

You can easily add logging facilities to your project, if you’ve got the logging dependency in your build.sbt file:

"ch.qos.logback" % "logback-classic" % "1.4.11" % "runtime"

In your servlet or filter class:

import org.slf4j.{Logger, LoggerFactory}

class YourServlet extends ScalatraServlet {

  val logger =  LoggerFactory.getLogger(getClass)

  get("/") {
    // whatever else you want to put in the body of the action

This will get you basic logging support. There are some additional logging libraries you might want to investigate like scala-logging, which act as Scala wrappers around slf4j.

The Scala wrappers use by-name parameters for the log message, and check to see that the logging level is enabled. This is a performance win for complex log messages involving expensive toStrings or many concatenations.