Issue with picocli and GraalVM native-image

Question

I'm trying to build a Java application which will be built into a Linux command line application using native-image provided by GraalVM. I have the below code:

@CommandLine.Command(
        name = "my-application",
        mixinStandardHelpOptions = true,
        helpCommand = true,
        version = "my-application 1.0",
        description = "My file manipulation application."
)
public class MyApplication implements Callable<Integer> {

    private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper(new YAMLFactory()
            .enable(YAMLGenerator.Feature.LITERAL_BLOCK_STYLE)
            .disable(YAMLGenerator.Feature.WRITE_DOC_START_MARKER)
    );

    @CommandLine.Parameters(index = "0", description = "The source file.")
    private File sourceFile;

    @CommandLine.Parameters(index = "1", description = "The target files.")
    private List<File> targetFiles;

    @CommandLine.Option(names = {"-env", "--environment"}, defaultValue = "TEST")
    private Environment environment; // TEST or PROD

    @CommandLine.Spec CommandLine.Model.CommandSpec spec;

    public static void main(String[] args) {
        int exitCode = new CommandLine(new MyApplication()).execute(args);
        System.exit(exitCode);
    }

    @Override
    public Integer call() throws Exception {
        spec.commandLine()
                .getOut()
                .println("Starting my-application tool execution...");

        // Some file manipulation using Jackson.

        spec.commandLine().getOut().println("Execution finished successfully.");

        return 0;
    }

I build the JAR with maven package and this jar has all needed dependencies. Then I build the native application with:

native-image -jar my-application-1.0-SNAPSHOT-jar-with-dependencies.jar -H:+ReportExceptionStackTraces --no-fallback

And when running the application with:

./my-application-1.0-SNAPSHOT-jar-with-dependencies inputfile.txt outputfile1.txt outputfile2.txt

I get the following error:

Exception in thread "main" picocli.CommandLine$InitializationException: picocli.CommandLine$AutoHelpMixin@62037019 is not a command: it has no @Command, @Option, @Parameters or @Unmatched annotations
    at picocli.CommandLine$Model$CommandReflection.validateCommandSpec(CommandLine.java:11680)
    at picocli.CommandLine$Model$CommandReflection.extractCommandSpec(CommandLine.java:11510)
    at picocli.CommandLine$Model$CommandSpec.forAnnotatedObject(CommandLine.java:6236)
    at picocli.CommandLine$Model$CommandSpec.mixinStandardHelpOptions(CommandLine.java:7220)
    at picocli.CommandLine$Model$CommandReflection.extractCommandSpec(CommandLine.java:11505)
    at picocli.CommandLine$Model$CommandSpec.forAnnotatedObject(CommandLine.java:6236)
    at picocli.CommandLine.<init>(CommandLine.java:227)
    at picocli.CommandLine.<init>(CommandLine.java:221)
    at picocli.CommandLine.<init>(CommandLine.java:196)
    at com.test.MyApplication.main(MyApplication.java:42)

The application works fine when I run it via IntelliJ or a simple java -jar command.

I tried a few things, as removing mixinStandardHelpOptions and helpCommand, but I start getting errors like "Unmatched arguments from index 0" or NullPointer with the spec (for printing outputs).

Before introducing picocli I was successfully able to run the native application and manipulating the files with ObjectMapper, so I believe that the packaging and image building procedure is correct.

Tried to follow the tip here:

https://github.com/remkop/picocli/issues/631

But I'm not sure how to proceed, tried adding something like

@Reflections({
        @Reflection(scanClass = CommandLine.Mixin.class),
        @Reflection(scanClass = CommandLine.HelpCommand.class)
})

But nothing changed.

Any help would be appreciated :)

Answer 1

Just found out that I was missing a dependency:

<!-- https://mvnrepository.com/artifact/info.picocli/picocli-codegen -->
<dependency>
    <groupId>info.picocli</groupId>
    <artifactId>picocli-codegen</artifactId>
    <version>4.6.3</version>
</dependency>

For more information:

https://www.infoq.com/articles/java-native-cli-graalvm-picocli/