quarkusio/quarkus · error · IllegalArgumentException

'target' can only be a class, a field or a method

Error message

'target' can only be a class, a field or a method: <target>

What it means

BuildTimeConditionBuildItem wraps the target of an @IfBuildTimeClass/@IfBuildTimeProfile-style annotation evaluation, and only CLASS, METHOD and FIELD annotation targets are supported. Any other AnnotationTarget.Kind (e.g. PARAMETER, TYPE) passed to the constructor throws IllegalArgumentException.

Solutions

1. Only create the build item for CLASS, METHOD or FIELD targets
2. Filter/ignore targets of other kinds before constructing the item
3. Move the conditional annotation to a supported target (class/field/method)

Example fix

// before
conditions.produce(new BuildTimeConditionBuildItem(paramTarget, enabled));
// after
if (EnumSet.of(Kind.CLASS, Kind.METHOD, Kind.FIELD).contains(target.kind())) {
    conditions.produce(new BuildTimeConditionBuildItem(target, enabled));
}

if (!EnumSet.of(AnnotationTarget.Kind.CLASS, AnnotationTarget.Kind.METHOD, AnnotationTarget.Kind.FIELD).contains(target.kind())) { skip; }

boolean isSupportedTarget(AnnotationTarget t) {
    return t.kind() == AnnotationTarget.Kind.CLASS
        || t.kind() == AnnotationTarget.Kind.METHOD
        || t.kind() == AnnotationTarget.Kind.FIELD;
}

When it happens

Trigger: Constructing BuildTimeConditionBuildItem with an AnnotationTarget whose kind is not CLASS, METHOD or FIELD — typically when a transformer/processor incorrectly forwards a parameter- or type-annotated target.

Common situations: Custom Arc transformers handling @IfBuildXxx annotations on method parameters or type uses and creating a build item from them; library upgrades changing where an annotation can be placed.

Related errors

• A matching predicate must be set!
• AnnotationTransformation is not an AnnotationsTransformer
• Different default scopes defined for additional bean class
• Invalid configuration value set for…
• Invalid regex pattern

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/2792de6fa5f133d7. Report an issue: GitHub.

Appendix: source

Thrown at extensions/arc/deployment/src/main/java/io/quarkus/arc/deployment/BuildTimeConditionBuildItem.java:20

import org.jboss.jandex.AnnotationTarget;

import io.quarkus.builder.item.MultiBuildItem;

public final class BuildTimeConditionBuildItem extends MultiBuildItem {

    private final AnnotationTarget target;
    private final boolean enabled;

    public BuildTimeConditionBuildItem(AnnotationTarget target, boolean enabled) {
        switch (target.kind()) {
            case CLASS:
            case METHOD:
            case FIELD:
                this.target = target;
                break;
            default:
                throw new IllegalArgumentException("'target' can only be a class, a field or a method: " + target);
        }
        this.enabled = enabled;
    }

    public AnnotationTarget getTarget() {
        return target;
    }

    public boolean isEnabled() {
        return enabled;
    }
}

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