quarkusio/quarkus · error · IllegalArgumentException

Couldn't find id field of

Error message

Couldn't find id field of 

What it means

During REST Data Panache build-time generation, EntityClassHelper.getIdField walks the entity's class hierarchy via Jandex looking for an @Id field. If none is found up the chain, it throws IllegalArgumentException naming the entity class.

Source

Thrown at extensions/panache/mongodb-rest-data-panache/deployment/src/main/java/io/quarkus/mongodb/rest/data/panache/deployment/EntityClassHelper.java:44

    public FieldInfo getIdField(String className) {
        return getIdField(index.getClassByName(DotName.createSimple(className)));
    }

    private FieldInfo getIdField(ClassInfo classInfo) {
        ClassInfo tmpClassInfo = classInfo;
        while (tmpClassInfo != null) {
            for (FieldInfo field : tmpClassInfo.fields()) {
                if (field.type().name().equals(OBJECT_ID) || field.hasAnnotation(BSON_ID_ANNOTATION)) {
                    return field;
                }
            }
            if (tmpClassInfo.superName() != null) {
                tmpClassInfo = index.getClassByName(tmpClassInfo.superName());
            } else {
                tmpClassInfo = null;
            }
        }
        throw new IllegalArgumentException("Couldn't find id field of " + classInfo);
    }

    public MethodDescriptor getSetter(String className, FieldInfo field) {
        return getSetter(index.getClassByName(DotName.createSimple(className)), field);
    }

    private MethodDescriptor getSetter(ClassInfo entityClass, FieldInfo field) {
        if (entityClass == null) {
            return null;
        }
        MethodInfo methodInfo = entityClass.method(JavaBeanUtil.getSetterName(field.name()), field.type());
        if (methodInfo != null) {
            return MethodDescriptor.of(methodInfo);
        } else if (entityClass.superName() != null) {
            return getSetter(index.getClassByName(entityClass.superName()), field);
        }
        return null;
    }

View on GitHub (pinned to e1c734241f)

Solutions

1. Add an @Id annotated field (e.g. public ObjectId id;) to the entity class or one of its superclasses.
2. Verify the superclass holding the id is part of the application and indexed (not an unindexed external jar without Jandex).
3. Ensure you use a supported id annotation from the Panache stack (@Id / ObjectId).

Example fix

// before
public class Book {
    public String isbn; // no @Id
}
// after
public class Book {
    @Id
    public ObjectId id;
    public String isbn;
}

// application-side check at startup
if (Book.class.getDeclaredFields().stream().noneMatch(f -> f.isAnnotationPresent(Id.class))) {
    throw new IllegalStateException("Book has no @Id field");
}

When it happens

Trigger: Using mongodb-rest-data-panache with an entity/repository whose entity class has no field annotated @Id (or whose @Id is on an unsupported ancestor not in the index).

Common situations: Migrating entities from another persistence framework that names ids differently (e.g. 'key' without @Id); manually written entities that forgot @Id; ObjectId id fields defined in a parent class excluded from the Jandex index.

Related errors

• Couldn't find id field of ${classInfo}
• Update types are only supported in MongoDB contexts
• Could not find indexed method: . with descriptor and arg ty
• Failed to process ${path}
• Annotation instance ${annotationInstance} does not match ann

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/d292f0ff7e7950e7. Report an issue: GitHub.