Standalone deployment

Launching Scalatra as a servlet

We need some glue code to launch an embedded Jetty server with the ScalatraListener.

package com.example  // remember this package in the sbt project definition
import org.eclipse.jetty.server.Server
import org.eclipse.jetty.servlet.{DefaultServlet, ServletContextHandler}
import org.eclipse.jetty.webapp.WebAppContext
import org.scalatra.servlet.ScalatraListener

object JettyLauncher { // this is my entry object as specified in sbt project definition
  def main(args: Array[String]): Unit = {
    val port = if(System.getenv("PORT") != null) System.getenv("PORT").toInt else 8080

    val server = new Server(port)
    val context = new WebAppContext()
    context setContextPath "/"
    context.setResourceBase("src/main/webapp")
    context.addEventListener(new ScalatraListener)
    context.addServlet(classOf[DefaultServlet], "/")

    server.setHandler(context)

    server.start
    server.join
  }
}

Be sure to define the appropriate ScalatraBootstrap:

import org.scalatra.LifeCycle
import javax.servlet.ServletContext
import org.scalatra.TemplateExample // this is the example Scalatra servlet

class ScalatraBootstrap extends LifeCycle {
  override def init(context: ServletContext) {
    context mount (new TemplateExample, "/*")
  }
}

The ScalatraBootstrap can be in the usual place, but if you would like to specify a specific package and class, you can do so with an init parameter:

    ...
    context setContextPath "/"
    context.setResourceBase("src/main/webapp")
    context.setInitParameter(ScalatraListener.LifeCycleKey, "org.yourdomain.project.ScalatraBootstrap")
    context.addEventListener(new ScalatraListener)
    ...

You’ll also need to ensure that the jetty-webapp library dependency in build.sbt contains a compile directive. Assuming your jetty-webapp declaration looks something like this:

"org.eclipse.jetty" % "jetty-webapp" % "9.2.15.v20160210" % "container",

change container to container;compile:

"org.eclipse.jetty" % "jetty-webapp" % "9.2.15.v20160210" % "container;compile",

Note: If sbt complains that configuration 'container' doesn’t exist, add and enable the sbt-scalatra to your project.

With the sbt-assembly plugin you can make a launchable jar. Now save this alongside your Scalatra project as JettyLauncher.scala and run sbt clean assembly. You’ll have the ultimate executable jar file in the target soon. Try

java -jar **-assembly-**.jar

and see it will launch the embedded Jetty at port 8080 with the example Scalatra project running. On an OS X 10.6 machine with JVM 1.6, this setup costs ~38MB memory.