Custom Package Formats

This section provides an overview of different packaging flavors.

SBT Assembly

Main Goal

Create a fat-jar with sbt-assembly in order to deliver a single,
self-containing jar as a package instead of the default lib/ structure

First add the sbt-assembly plugin to your plugins.sbt file.

addSbtPlugin("com.eed3si9n" % "sbt-assembly" % "0.11.2")

The next step is to remove all the jar mappings from the normal mappings and only add the assembly jar. In this example we’ll set the assembly jar name ourself, so we know exactly what the output should look like. Finally we change the scriptClasspath so it only contains the assembled jar. This is what the final build.sbt should contain:

import AssemblyKeys._

// the assembly settings

// we specify the name for our fat jar
assembly / jarName := "assembly-project.jar"

// using the java server for this application. java_application is fine, too

// removes all jar mappings in universal and appends the fat jar
Universal / mappings := {
    // universalMappings: Seq[(File,String)]
    val universalMappings = (Universal / mappings).value
    val fatJar = (Compile / assembly).value
    // removing means filtering
    val filtered = universalMappings filter {
        case (file, name) =>  ! name.endsWith(".jar")
    // add the fat jar
    filtered :+ (fatJar -> ("lib/" + fatJar.getName))

// the bash scripts classpath only needs the fat jar
scriptClasspath := Seq( (assembly / jarName).value )


Main Goal

Create a package that contains a single fat-jar that has been shrunken / optimized / obfuscated with proguard.

First add the sbt-proguard plugin to the plugins.sbt file:

addSbtPlugin("com.lightbend.sbt" % "sbt-proguard" % "0.3.0")

Then configure the proguard options in build.sbt:


// to configure proguard for scala, see
Proguard / proguardOptions ++= Seq(
  // ...

// specify the entry point for a standalone app
Proguard / proguardOptions += ProguardOptions.keepMain("com.example.Main")

Proguard / proguardVersion := "6.0.3"

// filter out jar files from the list of generated files, while
// keeping non-jar output such as generated launch scripts
Universal / mappings := (Universal / mappings).value.
  filter {
    case (file, name) => !name.endsWith(".jar")

// ... and then append the jar file emitted from the proguard task to
// the file list
Universal / mappings ++= (Proguard / proguard). => jar -> ("lib/" + jar.getName))

// point the classpath to the output from the proguard task
scriptClasspath := (Proguard / proguard) => jar.getName)

Now when you package your project using a command such as sbt Universal/packageZipTarball, it will include fat jar that has been created by proguard rather than the normal output in /lib.

Multi Module Builds

Main Goal

Aggregate multiple projects into one native package

If you want to aggregate different projects in a multi module build to a single package, you can specify everything in a single build.sbt

import NativePackagerKeys._

name := "mukis-fullstack"

// used like the groupId in maven
ThisBuild / organization := "de.mukis"

// all sub projects have the same version
ThisBuild / version := "1.0"

ThisBuild / scalaVersion := "2.11.2"

// common dependencies
ThisBuild / libraryDependencies ++= Seq(
    "com.typesafe" % "config" % "1.2.0"

// this is the root project, aggregating all sub projects
lazy val root = Project(
    id = "root",
    base = file("."),
    // configure your native packaging settings here
    settings = packageArchetype.java_server++ Seq(
        maintainer := "John Smith <[email protected]>",
        packageDescription := "Fullstack Application",
        packageSummary := "Fullstack Application",
        // entrypoint
        Compile / mainClass := Some("de.mukis.frontend.ProductionServer")
    // always run all commands on each sub project
    aggregate = Seq(frontend, backend, api)
) dependsOn(frontend, backend, api) // this does the actual aggregation

// --------- Project Frontend ------------------
lazy val frontend = Project(
    id = "frontend",
    base = file("frontend")
) dependsOn(api)

// --------- Project Backend ----------------
lazy val backend = Project(
    id = "backend",
    base = file("backend")
) dependsOn(api)

// --------- Project API ------------------
lazy val api = Project(
    id = "api",
    base = file("api")

Custom Packaging Format

Main Goal

Use native packager to define your own custom packaging format
and reuse stuff you already like

The very core principle of native packager are the mappings. They are a sequence of File -> String tuples, that map a file on your system to a location on your install location.

Defining a custom mapping format is basically transforming these mappings into the format of you choice. To do so, we recommend the following steps

  1. Create a new configuration scope for you packaging type

  2. Define a packageBin task in your new scope that transforms the mappings into a package

The following examples demonstrates how to create a simple text format, which lists all your mappings inside a package format. A minimal build.sbt would look like this

import NativePackagerKeys._

val TxtFormat = config("txtFormat")

val root ="."))
    // adding your custom configuration scope
    .configs( TxtFormat )
        name := "mukis-custom-package",
        version := "1.0",
        Compile / mainClass := Some("de.mukis.ConfigApp"),
        Linux / maintainer := "Nepomuk Seiler <[email protected]>",
        Linux / packageSummary := "Custom application configuration",
        packageDescription := "Custom application configuration",
        // defining your custom configuration
        TxtFormat / packageBin := {
            val fileMappings = (Universal / mappings).value
            val output = target.value / s"${packageName.value}.txt"
            // create the is with the mappings. Note this is not the ISO format -.-
            IO.write(output, "# Filemappings\n")
            // append all mappings to the list
            fileMappings foreach {
                case (file, name) => IO.append(output, s"${file.getAbsolutePath}\t$name${IO.Newline}")

To create your new “packageFormat” just run

TxtFormat / packageBin

If you want to read more about sbt configurations: