apache/maven · error · IllegalArgumentException

Unsupported class-loading strategy '{classLoadingStrategy}'.

Error message

Unsupported class-loading strategy '{classLoadingStrategy}'. Supported values are: parent-first, plugin and self-first

What it means

Error "Unsupported class-loading strategy '{classLoadingStrategy}'. Supported values are: parent-first, plugin and self-first" thrown in apache/maven.

Source

Thrown at impl/maven-cli/src/main/java/org/apache/maven/cling/extensions/BootstrapCoreExtensionManager.java:190

        return Collections.unmodifiableList(extensions);
    }

    private CoreExtensionEntry createExtension(CoreExtension extension, List<Artifact> artifacts) throws Exception {
        String realmId = "coreExtension>" + extension.getGroupId() + ":" + extension.getArtifactId() + ":"
                + extension.getVersion();
        final ClassRealm realm = classWorld.newRealm(realmId, null);
        Set<String> providedArtifacts = Collections.emptySet();
        String classLoadingStrategy = extension.getClassLoadingStrategy();
        if (STRATEGY_PARENT_FIRST.equals(classLoadingStrategy)) {
            realm.importFrom(parentRealm, "");
        } else if (STRATEGY_PLUGIN.equals(classLoadingStrategy)) {
            coreExports.getExportedPackages().forEach((p, cl) -> realm.importFrom(cl, p));
            providedArtifacts = coreExports.getExportedArtifacts();
        } else if (STRATEGY_SELF_FIRST.equals(classLoadingStrategy)) {
            realm.setParentRealm(parentRealm);
        } else {
            throw new IllegalArgumentException("Unsupported class-loading strategy '"
                    + classLoadingStrategy + "'. Supported values are: " + STRATEGY_PARENT_FIRST
                    + ", " + STRATEGY_PLUGIN + " and " + STRATEGY_SELF_FIRST);
        }
        log.debug("Populating class realm {}", realm.getId());
        for (Artifact artifact : artifacts) {
            String id = artifact.getGroupId() + ":" + artifact.getArtifactId();
            if (providedArtifacts.contains(id)) {
                log.debug("  Excluded {}", id);
            } else {
                Path file = artifact.getPath();
                log.debug("  Included {} located at {}", id, file);
                realm.addURL(file.toUri().toURL());
            }
        }
        return CoreExtensionEntry.discoverFrom(
                realm,
                Collections.singleton(artifacts.get(0).getPath().toFile()),
                extension.getGroupId() + ":" + extension.getArtifactId(),

View on GitHub (pinned to e4093d4e12)

When it happens

Trigger: Thrown at impl/maven-cli/src/main/java/org/apache/maven/cling/extensions/BootstrapCoreExtensionManager.java:190 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of apache/maven@e4093d4e12 (2026-08-21). Data as JSON: /api/errors/e46ddcdaa7f47ba2. Report an issue: GitHub.