Apache Maven Compiler Plugin – Setting the --release of the Java Compiler

Setting the `--release` of the Java Compiler

Starting with 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 old -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>3.14.0</version>
        <configuration>
          <release>8</release>
        </configuration>
      </plugin>
    </plugins>
    [...]
  </build>
  [...]
</project>

Note: The value in the release parameter follows Java's new Version-String Scheme (JEP 223)} 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.

Usage on JDK 8

The --release option is not supported using JDK 8. However, since Compiler plugin version 3.13.0 you can use the release property also on JDK 8. The plugin will convert it to source and target automatically.

To enable a project that targets Java 8 to be built using JDK 8 and also JDK 9 or later requires the conditional usage of the --release option, when using a plugin version below 3.13.0 or compilerId different that javac.

This may be done through the use of a profile:

<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>

Since version 3.13.0 of the Compiler Plugin together with the default javac compilerId you don't need conditional parametrisation of release. The release parameter will only be effective for Java 9 or above, otherwise the source and target will be passed to the compiler.

So you can simply configure as:

<project>
 [...]
 <build>
   [...]
   <plugins>
     <plugin>
       <groupId>org.apache.maven.plugins</groupId>
       <artifactId>maven-compiler-plugin</artifactId>
       <version>3.14.0</version>
       <configuration>
         <release>8</release>
         <source>8</source>
         <target>8</target>
       </configuration>
     </plugin>
   </plugins>
   [...]
 </build>
 [...]
</project>