Native Image Maven Plugin

To simplify the generation of native images, Native Image now works out of Maven with the Native Image Maven Plugin.

You can build a native executable directly with Maven using the mvn package command without running the native-image command as a separate step. However, the Maven project that uses the plugin should be built on a JDK containing the native-image tool in <java.home>/lib/svm/bin/native-image (or <java.home>/jre/lib/svm/bin/native-image for a Java 8 JDK). GraalVM is such a JDK (if native-image has been previously installed with gu).

Next, add native-image-maven-plugin into the <plugins> section of the pom.xml file:

<plugin>
    <groupId>org.graalvm.nativeimage</groupId>
    <artifactId>native-image-maven-plugin</artifactId>
    <version>${graalvm.version}</version>
    <executions>
        <execution>
            <goals>
                <goal>native-image</goal>
            </goals>
            <phase>package</phase>
        </execution>
    </executions>
    <configuration>
        <skip>false</skip>
        <imageName>example</imageName>
        <buildArgs>
            --no-fallback
        </buildArgs>
    </configuration>
</plugin>

Last, add the org.graalvm.sdk library dependency in the <dependencies> list:

<dependency>
    <groupId>org.graalvm.sdk</groupId>
    <artifactId>graal-sdk</artifactId>
    <version>${graalvm.version}</version>
    <scope>provided</scope>
</dependency>

The plugin figures out which JAR files it needs to pass to the native image and what the executable main class should be. If the heuristics fails with the no main manifest attribute, in target/<name>.jar error, the main class should be specified in the <configuration> node of the plugin. When mvn package completes, an executable is ready for use, generated in the target directory of the project.

Maven Plugin Customization #

If you use Native Image Maven plugin, it will pick up all the configuration for your application stored below the META-INF/native-image/ resource location, as described in Native Image Build Configuration. It is also possible to customize the plugin within a <configuration> node. The following configurations are available.

1. Configuration parameter <mainClass>: if the execution fails with the no main manifest attribute, in target/<name>.jar error, the main class should be specified. By default the plugin consults several locations in the pom.xml file in the following order to determine what the main class of the image should be:
   • <maven-shade-plugin> <transformers> <transformer> <mainClass>
   • <maven-assembly-plugin> <archive> <manifest> <mainClass>
   • <maven-jar-plugin> <archive> <manifest> <mainClass>
2. Configuration parameter <imageName>: if an image filename is not set explicitly, use parameter <imageName> to provide a custom filename for the image.
3. Configuration parameter <buildArgs>: if you want to pass additional options for to the native image builder, use the <buildArgs> parameter in the definition of the plugin. For example, to build a native image with assertions enabled that uses com.test.classname as a main class, add:

<configuration>
    <imageName>executable-name</imageName>
    <mainClass>com.test.classname</mainClass>
    <buildArgs>
        --no-fallback
    </buildArgs>
    <skip>false</skip>
</configuration>

If you use GraalVM Enterprise as the JAVA_HOME environment, the plugin builds a native image with Enterprise features enabled, e.g., an executable will automatically be built with compressed references and other optimizations enabled.

Reusing configuration from a parent POM #

The <buildArgs> element can be combined between parent and children POM. Suppose the following parent POM definition:

<plugin>
    <groupId>org.graalvm.nativeimage</groupId>
    <artifactId>native-image-maven-plugin</artifactId>
    <version>${graalvm.version}</version>
    <configuration>
        <imageName>${project.artifactId}</imageName>
        <mainClass>${exec.mainClass}</mainClass>
        <buildArgs>
            <buildArg>--no-fallback<buildArg>
        </buildArgs>
    </configuration>
</plugin>

Children projects have the ability to append <buildArg>s in the following way:

<plugin>
    <groupId>org.graalvm.nativeimage</groupId>
    <artifactId>native-image-maven-plugin</artifactId>
    <configuration>
        <buildArgs combine.children="append">
            <buildArg>--verbose</buildArg>
        </buildArgs>
    </configuration>
</plugin>

In this case, the arguments that will be passed to the native-image executable will be:

--no-fallback --verbose