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JVM library

Use the jvm/lib product type in a module to build a JVM library.

Module layout

Here is an overview of the module layout for a JVM library:

my-module/
├─ resources/ # (1)!
│  ╰─ logback.xml # (2)!
├─ src/
│  ├─ lib.kt
│  ╰─ Util.java # (3)!
├─ test/
│  ╰─ LibTest.java # (4)!
│  ╰─ UtilTest.kt
├─ testResources/
│  ╰─ logback-test.xml # (5)!
╰─ module.yaml
  1. Resources placed here are copied into the resulting JAR.
  2. This is just an example resource and can be omitted.
  3. You can mix Kotlin and Java source files in a single module, all in the src folder.
  4. You can test Java code with Kotlin tests or Kotlin code with Java tests.
  5. This is just an example resource and can be omitted.

Maven compatibility layout for JVM-only modules

If you're migrating from Maven, you can also configure the Maven-like layout

Packaging

The kotlin package command isn't defined by default for JVM libraries.

If publishing to Maven Central is enabled, then kotlin package creates a Maven Central ZIP bundle that is ready to be uploaded to the Central Portal. More specifically, enabling Maven Central publication provides the maven-central-bundle packaging format, and because it's the only one, it means the kotlin package command is effectively kotlin package --format=maven-central-bundle.

Publishing

The kotlin publish <repository> command can be used to publish the library to a Maven repository. Read more about this in the publishing guide.