GraalVM support for native images

[klopfdreh]

Description

Because we want to use jgit in GraalVM native images it would be great if this could be achieved through this ticket.

Motivation

jgit in GraalVM native images.

Alternatives considered

N/A

Additional context

N/A

Spring Boot Workaround

@Configuration
@ImportRuntimeHints(GitHubRuntimeHints.class)
@Slf4j
public class GitHubRuntimeHints implements RuntimeHintsRegistrar {

    @Override
    public void registerHints(RuntimeHints hints, ClassLoader classLoader) {
        Arrays.stream(System.getProperty("java.class.path").split(File.pathSeparator)).forEach(classpathEntry -> {
            // If the classpathEntry is no jar skip it
            if (!classpathEntry.endsWith(".jar")) {
                return;
            }

            try (JarInputStream is = new JarInputStream(Files.newInputStream(Path.of(classpathEntry)))) {
                JarEntry entry = is.getNextJarEntry();
                while (entry != null) {
                    String entryName = entry.getName();
                    if (entryName.endsWith(".class") && entryName.startsWith("org/eclipse/jgit") && !entryName.contains("package-info")) {
                        String githubApiClassName = entryName.replace("/", ".");
                        String githubApiClassNameWithoutClass = githubApiClassName.substring(0, githubApiClassName.length() - 6);
                        log.info("Registered class {} for reflections and serialization.", githubApiClassNameWithoutClass);
                        hints.reflection().registerType(TypeReference.of(githubApiClassNameWithoutClass), MemberCategory.values());
                        hints.serialization().registerType(TypeReference.of(githubApiClassNameWithoutClass));
                    }
                    entry = is.getNextJarEntry();
                }
            } catch (IOException e) {
                log.warn("Error while reading jars", e);
            }
        });

        hints.reflection()
            .registerType(TypeReference.of(IOException.class),
                hint -> hint.withMembers(MemberCategory.values())
            );

        hints.resources()
            .registerPattern("application.yml");
    }
}

Before the native-image command is used you have to set the environment varialbes

# Git configuration home folder
ENV XDG_CONFIG_HOME=/writablePath/
# Don't read git system configuration
ENV GIT_CONFIG_NOSYSTEM=true

Important: this is not a good solution as it enables all jgit classes for reflections and serialization.

An example of a native build can be found here: https://github.com/klopfdreh/native-cloud-config-test/blob/main/client/Dockerfile (Note: This does not use builder-image with multi stage and is only an example)