Maven Java 9

Different ways to build projects on Java 9 with Maven. The goal is to be able to simply run mvn clean install and then launch the resulting JAR with java -jar target/demo-java-9.jar.

• <executable>
• .mavenrc
• toolchain

Some approaches are more intrusive, others more brittle - have a look at the individual solutions for a small discussion of its pros and cons.

💥 Compiler Arguments 💥

In case you're trying to use some of the new command line options like --add-modules, be aware that the following doesn't work:

<plugin>
	<groupId>org.apache.maven.plugins</groupId>
	<artifactId>maven-compiler-plugin</artifactId>
	<version>3.6.1</version>
	<configuration>
		<compilerArgs>
			<arg>--add-modules java.xml.bind</arg>
		</compilerArgs>
		<fork>true</fork>
	</configuration>
</plugin>

With this configuration I got errors like the following:

[INFO] -------------------------------------------------------------
[ERROR] COMPILATION ERROR :
[INFO] -------------------------------------------------------------
[ERROR] javac: invalid flag: --add-modules java.xml.bind
Usage: javac <options> <source files>
use --help for a list of possible options

Apparently it's common knowledge that <arg> will put arguments that contain a space into quotes before passing them, so I had to do the following instead:

<compilerArgs>
	<arg>--add-modules</arg><arg>java.xml.bind</arg>
</compilerArgs>

Obvious, right? 🤔