Groovy Java 9 modules support

Question

I've spent some time to migrate my project written in Groovy to Java 10. Now it's possible to compile and run it. But still it doesn't use any benefits of Java 9 modularity.
Googling about Groovy and Java 9 modules gives almost nothing.

So is it possible to migrate Groovy project to use JDK 10 with Project Jigsaw modules?

Answer 1

Well, after a few days of experiments I come up with the answer - yes, it is possible to use Groovy with Project Jigsaw modules.
But it needs some additional effort.

Let's say we have following file structure:

├── build
├── jigsaw
│   └── module
│       └── test
│           └── Application.groovy
├── lib
│   └── groovy.all.jar
└── module-info.java  

module-info.java

module main {
    requires groovy.all;
}

Application.groovy

package jigsaw.module.test

class Application {
    static void main(String[] args) {
        println "Hello module!"
    }
}

First of all we need to compile module-info.java file with javac instead of compiling all files using groovyc because groovy treats module file as closure.

Let's do it:

javac -d build --module-path lib/ module-info.java

--module-path will include our groovy.all.jar as automatic module with name derived from JAR-file name.

Next we need to compile Application.groovy

groovyc -d build jigsaw/module/test/Application.groovy

It goes smoothly.
After compilation we have module-info.class (aka module descriptor) and Application.class.

├── build
│   ├── jigsaw
│   │   └── module
│   │       └── test
│   │           └── Application.class
│   └── module-info.class
├── jigsaw
│   └── module
│       └── test
│           └── Application.groovy
├── lib
│   └── groovy.all.jar
└── module-info.java

Now let's try to run our compiled module.

java --module-path build:lib --module main/jigsaw.module.test.Application

And this is what we get

Error occurred during initialization of boot layer
java.lang.module.FindException: Unable to derive module descriptor for lib/groovy.all.jar
Caused by: java.lang.module.InvalidModuleDescriptorException: Provider class moduleName=groovy-all not in module

And what does it mean? I don't know. After a lot of googling I found something similar.

So we need to manually remove from JAR these files:

• /META-INF/services/org.codehaus.groovy.source.Extensions
• /META-INF/services/org.codehaus.groovy.runtime.ExtensionModule

Finally our Java module is able to start

java --module-path build:lib --module main/jigsaw.module.test.Application
Hello module!

---

All manipulations were done using Oracle JDK 10 and Groovy 2.4.15.