Configure packaging 

Use the packaged jar on classpaths instead of class directory 

By default, a project exports a directory containing its resources and compiled class files. Set exportJars to true to export the packaged jar instead. For example,

exportJars := true

The jar will be used by run, test, console, and other tasks that use the full classpath.

Add manifest attributes 

By default, sbt constructs a manifest for the binary package from settings such as organization and mainClass. Additional attributes may be added to the packageOptions setting scoped by the configuration and package task.

Main attributes may be added with Package.ManifestAttributes. There are two variants of this method, once that accepts repeated arguments that map an attribute of type java.util.jar.Attributes.Name to a String value and other that maps attribute names (type String) to the String value.

For example,

Compile / packageBin / packageOptions +=
  Package.ManifestAttributes(java.util.jar.Attributes.Name.SEALED -> "true")

Other attributes may be added with Package.JarManifest.

Compile / packageBin / packageOptions +=  {
  import java.util.jar.{Attributes, Manifest}
  val manifest = new Manifest
  manifest.getAttributes("foo/bar/").put(Attributes.Name.SEALED, "false")
  Package.JarManifest( manifest )
}

Or, to read the manifest from a file:

Compile / packageBin / packageOptions +=  {
  val file = new java.io.File("META-INF/MANIFEST.MF")
  val manifest = Using.fileInputStream(file)( in => new java.util.jar.Manifest(in) )
  Package.JarManifest( manifest )
}

Change the file name of a package 

The artifactName setting controls the name of generated packages. See the Artifacts page for details.

Modify the contents of the package 

The contents of a package are defined by the mappings task, of type Seq[(File,String)]. The mappings task is a sequence of mappings from a file to include in the package to the path in the package. See Mapping Files for convenience functions for generating these mappings. For example, to add the file in/example.txt to the main binary jar with the path “out/example.txt”,

Compile / packageBin / mappings += {
  (baseDirectory.value / "in" / "example.txt") -> "out/example.txt"
}

Note that mappings is scoped by the configuration and the specific package task. For example, the mappings for the test source package are defined by the Test / packageSrc / mappings task.