We will use spray-servlet to build a war file of our API. So we can run it in a java app server. I assume we already have a working REST API. We will need a web.xml, under src/main/webapp/WEB-INF/:

<?xml version="1.0"?>
<web-app>
 <listener>
 <listener-class>spray.servlet.Initializer</listener-class>
 </listener>

 <servlet>
 <servlet-name>SprayConnectorServlet</servlet-name>
 <servlet-class>spray.servlet.Servlet30ConnectorServlet</servlet-class>
 <async-supported>true</async-supported>
 </servlet>

 <servlet-mapping>
 <servlet-name>SprayConnectorServlet</servlet-name>
 <url-pattern>/*</url-pattern>
 </servlet-mapping>
</web-app>

We need an sbt plugin to build wars. Add this to project/plugins.sbt:

addSbtPlugin("com.earldouglas" % "xsbt-web-plugin" % "1.0.0")

We’ll add dependencies to build.sbt, and also extra tasks:

name := "exampleAPI"

version := "1.0"

scalaVersion := "2.11.2"

libraryDependencies ++= {
 val akkaVersion = "2.3.6"
 val sprayVersion = "1.3.2"
 Seq(
 "io.spray" %% "spray-can" % sprayVersion,
 "io.spray" %% "spray-servlet" % sprayVersion, //We need spray-servlet
 "io.spray" %% "spray-routing" % sprayVersion,
 "io.spray" %% "spray-json" % "1.3.1",
 "io.spray" %% "spray-testkit" % sprayVersion % "test",
 "org.scalatest" %% "scalatest" % "2.2.4" % "test",
 "com.typesafe.akka" %% "akka-actor" % akkaVersion,
 "com.typesafe.akka" %% "akka-testkit" % akkaVersion % "test",
 "com.typesafe.akka" %% "akka-slf4j" % akkaVersion,
 "ch.qos.logback" % "logback-classic" % "1.1.2"
 )
}

//This adds tomcat dependencies, you can also use jetty()
tomcat() 

We’ll need to extend spray.servlet.WebBoot:

import akka.actor.{Props, ActorSystem}
import spray.servlet.WebBoot

// this class is instantiated by the servlet initializer
// it needs to have a default constructor and implement
// the spray.servlet.WebBoot trait
class Boot extends WebBoot {
 //we need an ActorSystem to host our application in
 implicit val system = ActorSystem("SprayApiApp")
 
 //create apiActor
 val apiActor = system.actorOf(Props[ApiActor], "apiActor")

 // the service actor replies to incoming HttpRequests
 val serviceActor = apiActor
}

And add a reference to this class in application.conf:

spray.servlet {
boot-class = “Boot”
}

• on spray.io is a good example application

Now we can run sbt package to build a war. And in sbt, use container:start to start a tomcat server with our application. And container:stop to stop it.

A good way to restart the server every time we change code is:

~container:start