Other JVM languages

Jenesis is not a Java-only build tool. Drop .kt, .scala or .groovy sources into a module and it resolves the matching compiler and builds them, mixed freely with Java, into one modular jar and its generated POM, with no build script to write. You do not turn a language on. Jenesis detects it from the file extensions present and wires the right compiler into the same step graph Core concepts described.

This chapter covers what changes when a module holds more than Java: how two compilers share one module, the one rule that decides which packages you can export, the standard-library dependency each language needs, and how to run a compiler plugin.

One module, two compilers

A mixed module is compiled by two compilers in sequence. Jenesis runs the other-language compiler and javac in a fixed order over the same sources, each producing its own classes into the module. Because both write into one module, the exported jar looks exactly like a single-language one - a consumer never sees the seam.

The order is not arbitrary, and it differs by language:

For Kotlin and Scala, the language compiler runs first: it reads your .java files only to resolve symbols (so Sample.kt can call a Java Greeter) but leaves the Java output to javac, which compiles the .java sources and module-info.java afterwards. For Groovy it is the mirror image: javac runs first and owns all Java output, then groovyc compiles the .groovy sources, reaching Java types through the classes javac already produced.

• Demo 41: Kotlin
• Demo 44: Scala
• Demo 46: Groovy

Which packages you can export

That order decides one thing you need to know: whether a package holding only non-Java code can be exported.

When javac validates an exports <package> directive, it checks that the package is populated in the module's output. For Kotlin and Scala this just works: their compiler already ran, so javac sees the Kotlin or Scala classes through --patch-module and accepts the export. You can export a package that contains a single Kotlin (or Scala) class and no Java type at all.

For Groovy you cannot. groovyc runs after javac, so at export-check time the package's Groovy classes do not exist yet and only Java types count. The rule is:

The standard-library dependency

Each language needs its standard library on the module path. You declare it as a normal requires in module-info.java, and Jenesis resolves it through Maven like any other dependency:

Groovy's jar carries an Automatic-Module-Name, so org.apache.groovy resolves as an automatic module. The Scala standard library lives entirely in one module - scala-library - with scala3-library_3 being an empty aggregator, so nothing splits package scala across two modules and the Java Module System accepts it on the module path with no hand-written wiring.

Pinning the compiler

Every language compiler resolves in its own dependency group - kotlinc, scalac or groovyc - kept completely apart from your module's own main-group dependencies. That separation matters: the running compiler is locked independently of the standard library your module ships against, so pinning a different kotlin-stdlib for your code can never downgrade the kotlinc that compiles it.

The compilers float a latest version by default. Run the pin step to record each resolved compiler jar with its version and SHA-256, exactly as it pins your Java compilers and dependencies (see Pinning & bills of materials):

java build/jenesis/Make.java pin

A compiler plugin

A Kotlin or Scala compiler plugin is declared exactly like a Java annotation processor (Building & running), with one addition: name the compiler first, so the plugin resolves in that compiler's own group rather than on javac's processor path.

/**
 * @jenesis.plugin kotlinc maven/org.jetbrains.kotlin/kotlin-serialization-compiler-plugin
 */
module demo.serialize {
    requires kotlinx.serialization.core;
}

Jenesis resolves the plugin under the kotlinc group, and the Kotlin compiler picks up the jar and loads it itself - you never name an entry point. Above, the kotlinx.serialization plugin generates a @Serializable class's serializer(), and the requires provides the annotation and the runtime types the generated code references. The Scala path is identical: @jenesis.plugin scalac <coordinate> resolves in the scalac group, and scalac loads the plugin the same way.

The plugin's version is pinned the usual way, coordinated to the compiler - the pin step writes back its @jenesis.pin line for you.

• Demo 43: Kotlin compiler plugin

API documentation

When you build documentation jars (jenesis.project.documentation, Building & running), each language uses its own documentation tool: Dokka for Kotlin, scaladoc for Scala, groovydoc for Groovy, javadoc for Java. You do not configure this; Jenesis scans the sources and picks tools to cover the languages present. When one tool can document every language in the module it runs alone and renders a single document: Java + Kotlin is one Dokka document, Java + Groovy one groovydoc document. Any mix that includes Scala, or Kotlin together with Groovy, splits the output, with javadoc rendering the Java at the archive root and each remaining language in its own subfolder. Either way the produced -javadoc.jar always has a root index.html, so it satisfies a repository like Maven Central.