quarkusio/quarkus · error · IllegalArgumentException

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

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.

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;
    }
}

View on GitHub (pinned to e1c734241f)

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

• Name cannot start with '/':${name}
• messageStarts cannot be empty
• AnnotationTransformation is not an AnnotationsTransformer: <
• Invalid configuration value set for 'quarkus.arc.remove-unus
• Different default scopes defined for additional bean class:

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