quarkusio/quarkus · error · RuntimeException

${classInfo.name()} has to be an interface

Error message

${classInfo.name()} has to be an interface

What it means

The REST Data Panache processor validates each discovered resource class and requires it to be a Java interface; a class bound to REST Data Panache is rejected at build time with this RuntimeException.

Source

Thrown at extensions/panache/hibernate-orm-rest-data-panache/deployment/src/main/java/io/quarkus/hibernate/orm/rest/data/panache/deployment/HibernateOrmPanacheRestProcessor.java:149

            List<ClassInfo> listenersForEntityType = getListenersByEntityType(index.getIndex(), resourceMethodListeners,
                    entityType);
            DataAccessImplementor dataAccessImplementor = new RepositoryDataAccessImplementor(repositoryClassName);
            String resourceClass = resourceImplementor.implement(
                    classOutput, dataAccessImplementor, resourceInterface, entityType, listenersForEntityType);
            // Make sure that repository bean is not removed and will be injected to the generated resource
            unremovableBeansProducer.produce(new UnremovableBeanBuildItem(
                    new UnremovableBeanBuildItem.BeanClassNameExclusion(repositoryClassName)));

            restDataResourceProducer.produce(new RestDataResourceBuildItem(
                    new ResourceMetadata(resourceClass, resourceInterface, entityType, idType,
                            getEntityFields(index.getIndex(), entityType))));
        }
    }

    private void validateResource(IndexView index, ClassInfo classInfo) {
        if (!Modifier.isInterface(classInfo.flags())) {
            throw new RuntimeException(classInfo.name() + " has to be an interface");
        }

        if (classInfo.interfaceNames().size() > 1) {
            throw new RuntimeException(classInfo.name() + " should only extend REST Data Panache interface");
        }

        if (!index.getKnownDirectImplementors(classInfo.name()).isEmpty()) {
            throw new RuntimeException(classInfo.name() + " should not be extended or implemented");
        }
    }

    private List<Type> getGenericTypes(ClassInfo classInfo) {
        return classInfo.interfaceTypes()
                .stream()
                .findFirst()
                .orElseThrow(() -> new RuntimeException(classInfo.toString() + " does not have generic types"))
                .asParameterizedType()
                .arguments();

View on GitHub (pinned to e1c734241f)

Solutions

1. Convert the resource from a class to an interface that extends PanacheEntityResource or PanacheRepositoryResource
2. Remove the class from REST Data Panache scanning if it was never meant to be a resource
3. Check imports/annotations so only the interface is registered

Example fix

// before
public class PersonResource implements PanacheEntityResource<Person, Long> {}
// after
public interface PersonResource extends PanacheEntityResource<Person, Long> {}

if (!resourceClass.isInterface())
    throw new IllegalStateException(resourceClass + " must be an interface extending a Panache REST Data resource");

static boolean isResourceInterface(Class<?> c) {
    return c.isInterface();
}

When it happens

Trigger: Annotating a concrete class with @ResourceClass or having the processor pick up a class (not interface) named/registered as an entity or repository resource in HibernateOrmPanacheRestProcessor.findEntityResources/findRepositoryResources.

Common situations: Typo: writing 'class MyResource implements ...' instead of 'interface MyResource extends ...'; copying a repository implementation into the scanned package.

Related errors

• ${classInfo.name()} should only extend REST Data Panache int
• ${classInfo.name()} should not be extended or implemented
• Couldn't find id field of ${classInfo}
• has to be an interface
• should only extend REST Data Panache interface

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/7c818ced09523f50. Report an issue: GitHub.