Demo .mavenrc

README.md

@@ -4,5 +4,6 @@ Different ways to build projects on Java 9 with Maven.
 The goal is to be able to simply run `mvn install` and then launch the resulting JAR with `java -jar target/demo-java-9.jar`.
 
 * [toolchain](toolchain)
+* [.mavenrc](mavenrc)
 
 Some approaches are more intrusive, others more brittle - have a look at the individual solutions for a small discussion of its pros and cons.

mavenrc/README.md

@@ -0,0 +1,19 @@
+# `mavenrc`
+
+Maven can apparently be configured with the [mostly undocumented][jira-mavenrc-doc] files `~/.mavenrc` (for current user) and `/etc/mavenrc` (for all users).
+In there, environment variables and command line options for the Java command can be configured.
+
+With this, it is easy to set `JAVA_HOME` just for the Maven command, which will lead to it running with the specified version.
+Here's the content of that file:
+
+```
+JAVA_HOME="/path/to/your/jdk-9"
+```
+
+## Pros and Cons
+
+If you not only want to compile with Java 9 but also use Java 9 features, you still have to specify the target `1.9` in your [pom](pom.xml).
+Note that this puts the pom into an awkward state where it is supposed to use JDK 9 but does not reference where it might come from (unlike the [toolchain approach](../toolchain))
+
+
+[jira-mavenrc-doc]: https://issues.apache.org/jira/browse/MNGSITE-246

mavenrc/pom.xml

@@ -0,0 +1,41 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+				 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+				 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+
+	<groupId>org.codefx.demo.mvn-java-9</groupId>
+	<artifactId>demo</artifactId>
+	<version>java-9</version>
+
+	<build>
+		<plugins>
+			<!-- target Java 9 -->
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-compiler-plugin</artifactId>
+				<version>3.6.1</version>
+				<configuration>
+					<source>1.9</source>
+					<target>1.9</target>
+					<release>9</release>
+				</configuration>
+			</plugin>
+			<!-- make resulting JAR executable -->
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-jar-plugin</artifactId>
+				<version>3.0.2</version>
+				<configuration>
+					<archive>
+						<manifest>
+							<addClasspath>true</addClasspath>
+							<mainClass>org.codefx.demo.mvn_java9.Main</mainClass>
+						</manifest>
+					</archive>
+				</configuration>
+			</plugin>
+		</plugins>
+	</build>
+
+</project>

mavenrc/src/main/java/org/codefx/demo/mvn_java9/Main.java

@@ -0,0 +1,18 @@
+package org.codefx.demo.mvn_java9;
+
+import static java.lang.StackWalker.Option.RETAIN_CLASS_REFERENCE;
+
+public class Main {
+
+	public static void main(String[] args) {
+		printCallerClass();
+	}
+
+	private static void printCallerClass() {
+				Class<?> callerClass = StackWalker
+				.getInstance(RETAIN_CLASS_REFERENCE)
+				.getCallerClass();
+		System.out.println(callerClass);
+	}
+
+}