Library for executing .kts files from regular Kotlin code
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Simon re-wrote tests to run on junit 5 jupiter; created custom exception ty…
…pe which is thrown for script loading errors; added feature to provide custom classloader to script loading
Latest commit 75583ad Nov 28, 2018


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KtsRunner is a light-weight tool that allows the execution of .kts (Kotlin Script) files from ordinary Kotlin programs. It's enabled by JSR 223 (Java Scripting Engines API).


Running a script from file system

A simple usage example for KtsRunner can be described as follows: The declaration of a class is placed in a .kts file, which is supposed to be loaded into a normal Kotlin program so that it can be processed further.

  1. Example class
data class ClassFromScript(val x: String)
  1. .kts file
import de.swirtz.ktsrunner.objectloader.ClassFromScript

ClassFromScript("I was created in kts")
  1. Code to load the object
val scriptReader = Files.newBufferedReader(Paths.get("path/classDeclaration.kts"))
val loadedObj: ClassFromScript = KtsObjectLoader().load<ClassFromScript>(scriptReader)
// >> I was created in kts

As shown, the KtsObjectLoader can be used for executing a .kts script and getting its result. The example shows a script that creates an instance of the ClassFromScript type that is loaded via KtsObjectLoader and then processed in the regular program.

Executing scripts directly

The KtsObjectLoader also allows the evaluation of simple String based scripts:

val scriptContent = "5 + 10"
val fromScript: Int = KtsObjectLoader().load<Int>(scriptContent))
// >> 15

Application Area

You might want to use KtsRunner when some part of your application's source has to be outsourced from the regular code. As an example, you can think of an application that provides a test suite runtime. The actual test cases are provided by a QA team which writes their test scripts using a domain specific language that is provided by the main application. Since you don't want QA to add source files (defining new test cases) to your application all the time, the test case creation is made via independent .kts (Kotlin Scripting) files in which the DSL is being utilized. The test suite main application can use the presented KtsRunner library for loading the test cases provided in .kts files and process them further afterward.

Controlling the ClassLoader

When instantiating an KtsObjectLoader, you can provide an explicit classloader as shown in this test case:

    fun `when passing a custom classloader, it should be used when loading the script`() {
        val myCl = object : ClassLoader() {
            override fun loadClass(name: String?): Class<*> {
                throw IllegalStateException()
       assertExceptionThrownBy<IllegalStateException> {

Getting Started

In your Gradle build, simply include the following repository and dependency:

maven { 
dependencies {