You can open this sample inside an IDE using the IntelliJ native importer or Eclipse Buildship.

This sample shows how to build a JNI library with Gradle implemented in Kotlin and C++; however, this applies to other native language as well. The library includes JUnit tests with minimal configuration.

build.gradle
plugins {
	id 'org.jetbrains.kotlin.jvm' version '1.3.72'
	id 'dev.nokee.jni-library'
	id 'dev.nokee.cpp-language'
}

repositories {
	jcenter()
}

dependencies {
	implementation platform('org.jetbrains.kotlin:kotlin-bom:1.3.72')
	implementation 'org.jetbrains.kotlin:kotlin-stdlib-jdk8'

	testImplementation 'org.jetbrains.kotlin:kotlin-test'
	testImplementation 'org.jetbrains.kotlin:kotlin-test-junit'
}
build.gradle.kts
plugins {
	id("org.jetbrains.kotlin.jvm") version "1.3.72"
	id("dev.nokee.jni-library")
	id("dev.nokee.cpp-language")
}

repositories {
	jcenter()
}

dependencies {
	implementation(platform(kotlin("bom")))
	implementation(kotlin("stdlib-jdk8"))

	testImplementation(kotlin("test"))
	testImplementation(kotlin("test-junit"))
}

To build and test the library:

$ ./gradlew build

BUILD SUCCESSFUL
7 actionable tasks: 7 executed

The JNI library produced inside ./build/libs directory:

$ ls ./build/libs/*.jar
./build/libs/kotlin-cpp-jni-library.jar

Since there is only one variant, the native component is included inside the main JAR:

$ jar tf ./build/libs/kotlin-cpp-jni-library.jar
META-INF/
META-INF/MANIFEST.MF
META-INF/kotlin-cpp-jni-library.kotlin_module
com/
com/example/
com/example/greeter/
com/example/greeter/NativeLoader.class
com/example/greeter/Greeter.class
com/example/greeter/Greeter$Companion.class
libkotlin-cpp-jni-library.dylib

For more information, see JNI Library Plugin and C++ Language Plugin reference chapters.