Gradle 6.4 Finally Supports Java Modules

2020 05 01 head

Java 9 release introduced the concept of modules within the Java language. Java 9 was released in September 2017.

Until now, creating Java modules was quite cumbersome and Gradle did only offer limited support through external plugins.

With the release of Gradle 6.4 in May 2020, software developers can finally easily generate well-behaved Java modules. We had to wait almost three years for native support!

Support for modules is native in the Java plugin.

You only need to add one configuration line.

Start using Java modules and have language support to enforce modularity in your product.

Java Modules in Gradle 6.4

Gradle supports the Java module system with everything you need to compile, test and execute tests for Java modules. You can also build Javadoc.

While there is some overlap with Gradle’s dependency management features, Java modules offer module boundaries that are enforced by the Java runtime. Modularity is enforced at the language level instead of coding conventions or using external tools such as ArchUnit.

The only thing you need to configure is module path inference for the Java plugins. [1]

 java {

Then you just need to make sure you write a proper Java module by providing a module information file. An example of a module information file is

 module net.tangly.fsm {
   exports net.tangly.fsm;
   exports net.tangly.fsm.dsl;
   exports net.tangly.fsm.utilities;
   requires org.apache.logging.log4j;
   requires static org.jetbrains.annotations;

Java 14 in Gradle Java 14 was also released in Spring 2020. It is worth experimenting with the new preview features. The following configuration is needed in Gradle to compile, test, execute and generate JavaDoc when using Java 14 preview features.

 tasks.withType(JavaCompile) {
     options.encoding = 'UTF-8'
     options.fork = true
     options.incremental = true
     options.warnings = true
     options.deprecation = true
     options.compilerArgs += ["-parameters", "--enable-preview", "-Xlint:unchecked"]
   tasks.withType(Test) {
     options {
       setExcludeTags(['integration', 'localTest'] as Set)
     jvmArgs += "--enable-preview"
     maxParallelForks = 8
     failFast = false
   tasks.withType(Javadoc) {
     enabled = true
     javadoc.options {
       addBooleanOption('-enable-preview', true)
       addStringOption('-release', '14')
   tasks.withType(JavaExec) {
     jvmArgs += '--enable-preview'

Beware that JaCoCo shall only release a version supporting code coverage for JDK 14 and, in particular, record not before June 2020.

1. Gradle 7.0 released in Spring 2021 transparently supports Java modules. If you use the java-library plugin, the support of Java modules is transparent.