quarkusio/quarkus · error · IllegalArgumentException

Unknown annotation attribute value:

Error message

Unknown annotation attribute value: 

What it means

Annotations.jandexAnnotationValue() converts a runtime annotation member value into a Jandex AnnotationValue. It handles primitives, String, Class, enum, nested annotations and arrays; any other Java type (arbitrary object) is rejected with IllegalArgumentException. Jandex annotation values must map to one of the metaspace-supported value kinds.

Source

Thrown at independent-projects/arc/processor/src/main/java/io/quarkus/arc/processor/Annotations.java:313

            return org.jboss.jandex.AnnotationValue.createEnumValue(name,
                    DotName.createSimple(((Enum<?>) value).getDeclaringClass().getName()), ((Enum<?>) value).name());
        } else if (value instanceof Class) {
            return org.jboss.jandex.AnnotationValue.createClassValue(name, Types.jandexType((Class<?>) value));
        } else if (value.getClass().isAnnotation()) {
            Class<? extends Annotation> annotationType = annotationType((Annotation) value);
            @SuppressWarnings("unchecked")
            org.jboss.jandex.AnnotationValue[] jandexAnnotationValues = jandexAnnotationValues(
                    (Class<Annotation>) annotationType, (Annotation) value);
            org.jboss.jandex.AnnotationInstance jandexAnnotation = org.jboss.jandex.AnnotationInstance.create(
                    DotName.createSimple(annotationType.getName()), null, jandexAnnotationValues);
            return org.jboss.jandex.AnnotationValue.createNestedAnnotationValue(name, jandexAnnotation);
        } else if (value.getClass().isArray()) {
            org.jboss.jandex.AnnotationValue[] jandexAnnotationValues = Arrays.stream(boxArray(value))
                    .map(it -> jandexAnnotationValue(name, it))
                    .toArray(org.jboss.jandex.AnnotationValue[]::new);
            return org.jboss.jandex.AnnotationValue.createArrayValue(name, jandexAnnotationValues);
        } else {
            throw new IllegalArgumentException("Unknown annotation attribute value: " + value);
        }
    }

    private static Object[] boxArray(Object value) {
        if (value instanceof boolean[]) {
            boolean[] primitiveArray = (boolean[]) value;
            Object[] boxedArray = new Boolean[primitiveArray.length];
            for (int i = 0; i < primitiveArray.length; i++) {
                boxedArray[i] = primitiveArray[i];
            }
            return boxedArray;
        } else if (value instanceof byte[]) {
            byte[] primitiveArray = (byte[]) value;
            Object[] boxedArray = new Byte[primitiveArray.length];
            for (int i = 0; i < primitiveArray.length; i++) {
                boxedArray[i] = primitiveArray[i];
            }
            return boxedArray;

View on GitHub (pinned to e1c734241f)

Solutions

1. Convert the value to a supported type: primitive, String, Class, enum constant, nested annotation, or flat array of these
2. For arrays, pass a proper Java array (not a List) of a supported component type
3. If building AnnotationInstance directly, use org.jboss.jandex.AnnotationValue.create* methods with matching kinds
4. Check the source annotation definition for a member typed outside CDI-allowed types

Example fix

// before
values.put("tags", List.of("a","b")); // List unsupported
// after
values.put("tags", new String[]{"a","b"});

static void checkValue(Object v) {
    boolean ok = v instanceof String || v instanceof Class || v instanceof Enum
        || v instanceof Annotation || v.getClass().isArray() || v instanceof Number || v instanceof Boolean || v instanceof Character;
    if (!ok) throw new IllegalArgumentException("Unsupported: " + v.getClass());
}

static boolean isJandexSafe(Object v) {
    return v == null || v instanceof String || v instanceof Class || v instanceof Enum
        || v instanceof Annotation || v.getClass().isArray();
}

try { AnnotationValue av = jandexAnnotationValue(name, val); }
catch (IllegalArgumentException e) { throw new IllegalArgumentException("Member '" + name + "' needs a Jandex-supported value", e); }

When it happens

Trigger: Building a synthetic AnnotationInstance (e.g. via Annotations.create/Jandex value conversion) whose member value is an unsupported object type — e.g. a List, Map, or custom POJO passed as an annotation attribute value.

Common situations: Extensions/tests constructing AnnotationInstance programmatically with wrong member values; reflection-extracted annotation maps containing unexpected types; version drift where a new value kind isn't handled.

Related errors

• Annotation does not have @Retention(RUNTIME):
• Annotation class not available:
• Value is not set for %s.%s(). Most probably an older version
• Class of nested annotation missing
• Array component kind is

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/65ce66bf0ffd7616. Report an issue: GitHub.