Is there a way to add maven dependencies while using the maven-jlink-plugin?

Question

I'm using this Github project to get exposed to the new modular features in Java 9. I would like to add dependencies to the project and be able to build a native image. However, when I try to add a new dependency to the pom.xml, and add the requires statement to the module-info.java, I get a the following error from the maven-jlink-plugin:

Error: module-info.class not found for joda.time module

I'm trying to use this as a proof of concept that I can deploy images using the new linking phase, but naturally I need to be able to have external dependencies and I need to use maven (work constraint).

Changes to mod-jar/pom.xml

...
 <dependencies>
    <dependency>
      <groupId>joda-time</groupId>
      <artifactId>joda-time</artifactId>
      <version>2.9.9</version>
    </dependency>
  </dependencies>
...

mod-jar/module-info.java

module com.soebes.nine.jar {
  requires java.base;
  requires joda.time;
  exports com.soebes.example.nine.jar;
}

Logs:

[INFO] --- maven-jlink-plugin:3.0.0-alpha-1:jlink (default-jlink) @ mod-jlink ---
[INFO] Toolchain in maven-jlink-plugin: jlink [ /Library/Java/JavaVirtualMachines/jdk-9.0.1.jdk/Contents/Home/bin/jlink ]
[INFO] The following dependencies will be linked into the runtime image:
[INFO]  -> module: com.soebes.nine.one ( /Users/sebastianrestrepo/Projects/jdk9-jlink-jmod-example/maven-example/mod-1/target/jmods/com.soebes.nine.one.jmod )
[INFO]  -> module: com.soebes.nine.two ( /Users/sebastianrestrepo/Projects/jdk9-jlink-jmod-example/maven-example/mod-2/target/jmods/com.soebes.nine.two.jmod )
[INFO]  -> module: com.soebes.nine.jar ( /Users/sebastianrestrepo/Projects/jdk9-jlink-jmod-example/maven-example/mod-jar/target/com.soebes.nine.jar-1.0-SNAPSHOT.jar )
[INFO]  -> module: joda.time ( /Users/sebastianrestrepo/.m2/repository/joda-time/joda-time/2.9.9/joda-time-2.9.9.jar )
[ERROR] 
Error: module-info.class not found for joda.time module
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary:
[INFO] 
[INFO] parent ............................................. SUCCESS [  1.460 s]
[INFO] com.soebes.nine.one ................................ SUCCESS [  2.022 s]
[INFO] com.soebes.nine.two ................................ SUCCESS [  1.392 s]
[INFO] com.soebes.nine.jar ................................ SUCCESS [  1.388 s]
[INFO] mod-jlink .......................................... FAILURE [  1.061 s]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 7.911 s
[INFO] Finished at: 2017-11-03T15:27:35-04:00
[INFO] Final Memory: 26M/981M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-jlink-plugin:3.0.0-alpha-1:jlink (default-jlink) on project mod-jlink: 

I would really appreciate any help. Thanks.

Answer 1

This has not much to do with the plugin I believe. Module joda.time in your case seems to be an automatic module.

The jlink tool does not support linking of automatic modules because they can rely on the arbitrary content of the classpath, which goes against the idea of a self-contained Java runtime.

So there are two ways to fix this probably :-

• (you don't own the jar) Temporarily go ahead create a module-info.java[you could use jdeps tool for it] and update the jar[using jar tool] with the corresponding compiled class as in projects under Java 9.

• (you own the dependency) Permanently migrate the jar to Java 9 itself, where it would consist of the module-info.class by itself after being compiled and packaged.

Answer 2

You could use the ModiTect Maven plug-in to add a module descriptor to the JAR and create a modular runtime image with that module.

Disclaimer: I'm the author of ModiTect.