Introduction

The Maven JMod plugin is used to create JMod Files in JDK 9.

Configuration of the Maven JMod Plugin

To use the Maven JMod Plugin you have to configure it as an extensions which means the configuration in your pom file has to look like this:

<project>
  [...]
  <build>
    [...]
    <plugins>
      [...]
      <plugin>
        <artifactId>maven-jmod-plugin</artifactId>
        <version>3.0.0-alpha-1</version>
        <extensions>true</extensions>
        <configuration>
          <!-- configuration elements goes here -->
        </configuration>
      </plugin>
   [...]
</project>

The configuration elements contains the configuration for the plugin like any other Maven plugin. The different elements which can be configured for this plugin can identified by the goals documentation.

Requirements

Based on the foundation of the plugin it is required to have JDK 9 installed. This means either you have it configured via JAVA_HOME which means to run the whole Maven build with JDK 9 or via Toolchains.

Howto configure Maven related to Toolchains can be read in the Toolchains documentation.

Usage of the Maven JMod Plugin

JMod files can contain supplemental configuration files, native libraries, legals notices, header files, man pages and native commands. The JMod files are intended to be used in relationship with JLink to produce Java Run Time Images.

An important thing to mention is that jmod files are not intended to be used for run time and usual module relationships (You can't run a jvm via java using jmod files). For such purposes jar files exists.

You can simply create a jmod file by defining the packaging jmod in your pom file.

The first-mod project looks similar like this (apart from the above configuration):

<project ...>
  <modelVersion>4.0.0</modelVersion>
   [...]
  <groupId>com.corporate.project</groupId>
  <artifactId>first-mod</artifactId>
  <verison>1.0-SNAPSHOT</version>
  <packaging>jmod</packaging>
   [...]
</project>

You can put supplemental configuration files, header files, native libraries, man pages into the appropriate directories. Furthermore you can add java source files etc. into this module and they will be compiled and later added to the resulting jmod file. An example source tree looks like this:

src/
└── main
    ├── cmds
    │   ├── first.cmd
    │   ├── first.sh
    │   └── test.sh
    ├── configs
    │   ├── config.1
    │   ├── config.2
    │   └── sub-configuration
    │       └── config.sub
    ├── headerfiles
    │   └── first.h
    ├── java
    │   ├── com
    │   │   └── corporate
    │   │       └── project
    │   │           └── Main.java
    │   └── module-info.java
    ├── legalnotices
    │   └── first.md
    ├── libs
    │   └── native-lib.so
    └── manpages
        └── the-page.man

The above directories like cmds, configs, headerfiles, legalnotices, libs, manpages are the default directories which are defined by the Maven JMod Plugin. If you really need different directories to be used you can of course configure this but we don't recommend this. You should follow convention over configuration paradigm.

Finally if you like to create the jmod file this can be achieved by using the following Maven call:

mvn clean package

There will be some output lines like this (This is configured using toolchains):

[INFO] --- maven-surefire-plugin:2.19.1:test (default-test) @ first-jmod ---
[INFO] Toolchain in maven-surefire-plugin: JDK[/../jdk1.9.0_ea+181.jdk/Contents/Home]
[INFO] No tests to run.
[INFO]
[INFO] --- maven-jmod-plugin:3.0.0-alpha-1:create (default-create) @ first-jmod ---
[INFO] Toolchain in maven-jmod-plugin: jmod [ /../jdk1.9.0_ea+181.jdk/Contents/Home/bin/jmod ]
[INFO]

If you like to install the resulting jmod file you can of course use:

mvn clean install

or if you like to deploy the resulting artifacts to a remote repository you have to use:

mvn clean deploy

The jmod files will be really installed/deployed as jmod file with the according extension.