Setting the --release of the Java Compiler

Starting JDK 9, the javac executable can accept the --release option to specify against which Java SE release you want to build the project. For example, you have JDK 11 installed and used by Maven, but you want to build the project against Java 8. The --release option ensures that the code is compiled following the rules of the programming language of the specified release, and that generated classes target the release as well as the public API of that release. This means that, unlike the -source and -target options, the compiler will detect and generate an error when using APIs that don't exist in previous releases of Java SE.

Since version 3.6 of the Compiler Plugin, this option can be provided either via a property:

<project>
  [...]
  <properties>
    <maven.compiler.release>8</maven.compiler.release>
  </properties>
  [...]
</project>

or by configuring the plugin directly:

<project>
  [...]
  <build>
    [...]
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.12.1</version>
        <configuration>
          <release>8</release>
        </configuration>
      </plugin>
    </plugins>
    [...]
  </build>
  [...]
</project>

Note: The value in the release parameter follows the new version naming scheme adopted since Java 9. As such, the release number does not start with 1.x anymore. Also note that the supported release targets include the release of the currently used JDK plus a limited number of previous releases.

<project>
  [...]
  <profiles>
    [...]
    <profile>
      <id>set-compiler-release</id>
      <activation>
        <jdk>[9,)</jdk>
      </activation>
      <properties>
        <maven.compiler.release>8</maven.compiler.release>
      </properties>
    </profile>
    [...]
  </profiles>
  [...]
</project>