Update 24th of March 2017

There seems to be quite a bit of interest on the subject, if you don’t find the answer to what you are looking for don’t hesitate to leave a comment and if I know the answer I’ll update the page so that everybody else can benefit from it.

Update 20th of February 2017

Maven 3.3.9 does not seem to work very well with java 9, Maven 3.2.5 is fine. seems to be some cglib access, there should be a way to open the package if I knew which one was failing.

To run the test with mockito

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-surefire-plugin</artifactId>

    <configuration>
        <argLine>--add-opens java.base/java.lang=ALL-UNNAMED</argLine>
    </configuration>
</plugin>

all the -XaddExports:java.base/sun.nio.ch=ALL-UNNAMED should now be replaced by --add-opens java.base/sun.nio.ch=ALL-UNNAMED

Update 2nd of November 2016

the Maven plugin 3.6.0 has been officially release with jigsaw support.

Gave it a quick try and I have some issues running/compiling the tests. seems that the test might need a module-info.java.

Will update when I have more info.

Also note that

Maven building java 9-ea with jigsaw

If you don’t have a module-info.java then you don’t need to change anything.

State of maven integration

Maven - Java 9 Jigsaw

maven-compiler-plugin

The maven-compiler-plugin on the branch maven-compiler-plugin_jigsaw-ea integrates with javac 9. There is no current release.

checkout

svn co http://svn.apache.org/repos/asf/maven/plugins/branches/maven-compiler-plugin_jigsaw-ea

build

cd maven-compiler-plugin_jigsaw-ea
mvn clean install

you can now use the plugin from your local repo.

I also have a version built available by adding the following to your pom

<pluginRepositories>
    <pluginRepository>
        <id>arnaudroger-maven-plugin-repository</id>
        <url>https://arnaudroger.github.io/maven</url>
    </pluginRepository>
</pluginRepositories>

profile

all you need to do now is to add a profile for jdk 9-ea with that plugin. You will also need to overwrite the asm dependency to 6.0_ALPHA to support the new bytecode version.

   <profile>
        <id>jdk19</id>
        <activation>
            <jdk>9-ea</jdk>
        </activation>
        <build>
            <plugins>
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <version>3.6-jigsaw-SNAPSHOT</version>
                    <configuration>
                        <source>9</source>
                        <target>9</target>
                    </configuration>
                    <dependencies>
                        <dependency>
                            <groupId>org.ow2.asm</groupId>
                            <artifactId>asm</artifactId>
                            <version>6.0_ALPHA</version>
                        </dependency>
                    </dependencies>
                </plugin>
            </plugins>
        </build>
    </profile>

module-info.java

The jigsaw maven-compiler-plugin will compile will switch to the modular build if module-info.java is present.

You can find more info at Jigsaw QuickStart. start with a empty one see what you need to import.

module mypackage {}

et Voila!

Potential troubles

ClassLoaders

The ClassLoader hierarchy is slightly changed. When you start your application you won’t get an URLClassLoader. if your code rely on that … your will need to change it.

third party library

Some third-party libraries depend on part of the jre that is no more accessible. You might need to add instruction to export those when running the unit tests or compiling - for preprocessor, note that you will need to then fork javac.

for the test

<profile>
    <id>jdk19</id>
    <activation>
        <jdk>9-ea</jdk>
    </activation>
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <configuration>
                    <argLine>-XaddExports:java.base/sun.nio.ch=ALL-UNNAMED -XaddExports:jdk.unsupported/sun.misc=ALL-UNNAMED</argLine>
                </configuration>
            </plugin>
        </plugins>
    </build>
</profile>

for the javac

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>3.6-jigsaw-SNAPSHOT</version>
    <configuration>
        <source>9</source>
        <target>9</target>
        <fork>true</fork>
        <compilerArgs>
            <arg>-J-XaddExports:jdk.compiler/com.sun.tools.javac.code=ALL-UNNAMED</arg>
            <arg>-J-XaddExports:jdk.compiler/com.sun.tools.javac.comp=ALL-UNNAMED</arg>
        </compilerArgs>
    </configuration>
    <dependencies>
        <dependency>
            <groupId>org.ow2.asm</groupId>
            <artifactId>asm</artifactId>
            <version>6.0_ALPHA</version>
        </dependency>
    </dependencies>
</plugin>

you can verify which dependencies a jar has by using jdeps

jdeps ~/.m2/repository/io/netty/netty-all/4.0.39.Final/netty-all-4.0.39.Final.jar

### netty You will need to export the following packages to run the code

java.base/sun.nio.ch
java.base/sun.security.util
java.base/sun.security.x509
jdk.unsupported/sun.misc

beware though that running in travis-ci it failed with the direct buffer, I had to deactivate the native epoll support.

-Dcassandra.native.epoll.enabled=false

Lombok

Currently as of 1.16.10 Lombok still has issues with java9 as it relies on classes that are not present anymore.

To get the preprocessor as far as you can you will need to add the following to the maven-compiler-plugin configuration.

<compilerArgs>
    <arg>-J-XaddExports:jdk.compiler/com.sun.tools.javac.code=ALL-UNNAMED</arg>
    <arg>-J-XaddExports:jdk.compiler/com.sun.tools.javac.comp=ALL-UNNAMED</arg>
    <arg>-J-XaddExports:jdk.compiler/com.sun.tools.javac.file=ALL-UNNAMED</arg>
    <arg>-J-XaddExports:jdk.compiler/com.sun.tools.javac.main=ALL-UNNAMED</arg>
    <arg>-J-XaddExports:jdk.compiler/com.sun.tools.javac.model=ALL-UNNAMED</arg>
    <arg>-J-XaddExports:jdk.compiler/com.sun.tools.javac.processing=ALL-UNNAMED</arg>
    <arg>-J-XaddExports:jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED</arg>
    <arg>-J-XaddExports:jdk.compiler/com.sun.tools.javac.tree=ALL-UNNAMED</arg>
</compilerArgs>

Osgi bundle

BND seems to work pretty well, there is only 2 config to add.

_noee, it does not recognise the java version and can’t generate the Require-Capabilities.
_failok, it fails on the module-info.class being at the root package.

<plugin>
    <groupId>org.apache.felix</groupId>
    <artifactId>maven-bundle-plugin</artifactId>
    <extensions>true</extensions>
    <version>3.2.0</version>
    <configuration>
        <instructions>
            <_noee>true</_noee>
            <_failok>true</_failok>
        </instructions>
    </configuration>
</plugin>