Scala SBT `build.sbt` example of hooking/injecting arbitrary shell commands and using non-native libraries in the build definition via a task run after successful compilation.

build.sbt

organization  := "org.foo.bar"

name := "JustAnExample"

version := "1.0"

scalaVersion := "2.10.3"

scalacOptions := Seq("-unchecked", "-deprecation", "-encoding", "utf8")

val foobar = taskKey[Unit]("foobar")

foobar := {
    // Run a shell command and print output.
    val process = java.lang.Runtime.getRuntime().exec("ls -al /");
    val reader = new java.io.BufferedReader(new java.io.InputStreamReader(process.getInputStream()))
    while (reader.ready()) {
        println(reader.readLine())
    }
    // Downlaoad files from S3.
    val auth = new com.amazonaws.auth.BasicAWSCredentials(java.lang.System.getenv("AWS_ACCESS_KEY"), java.lang.System.getenv("AWS_SECRET_KEY"))
    val client = new com.amazonaws.services.s3.AmazonS3Client(auth)
    val myFile = new File("/tmp/myFile")
    client.getObject(new com.amazonaws.services.s3.model.GetObjectRequest(System.getenv("AWS_S3_BUCKET_NAME"), fileName), myFile)
}

// Trigger after compilation.
foobar <<= foobar triggeredBy (compile in Compile)

project_plugins.sbt

// @see http://www.scala-sbt.org/0.13.5/docs/Extending/Plugins.html
libraryDependencies += "com.amazonaws" % "aws-java-sdk"  % "1.6.12"