quarkusio/quarkus · error · UnsupportedOperationException

Decorating built-in bean types is not supported! Decorator $

Error message

Decorating built-in bean types is not supported! Decorator ${decoratorClass} is attempting to decorate ${decoratedType.name()}

What it means

Arc forbids decorating built-in bean types such as Instance, Event, BeanManager, or resource types. If a decorator's decorated type's raw name matches a BuiltinBean, createDecorator throws this UnsupportedOperationException because interception of built-in beans is not supported.

Source

Thrown at independent-projects/arc/processor/src/main/java/io/quarkus/arc/processor/Decorators.java:102

        }
        if (decoratedTypes.isEmpty()) {
            throw new DefinitionException("The decorator " + decoratorClass + " has no decorated type");
        }

        // The delegate type of a decorator must implement or extend every decorated type
        Set<Type> delegateTypes = Types.getDelegateTypeClosure(delegateInjectionPoint, beanDeployment);
        for (Type decoratedType : decoratedTypes) {
            if (!delegateTypes.contains(decoratedType)) {
                throw new DefinitionException("The delegate type " + delegateInjectionPoint.getRequiredType()
                        + " does not implement the decorated type: " + decoratedType);
            }
            for (BuiltinBean bean : BuiltinBean.values()) {
                if (bean.equals(BuiltinBean.RESOURCE)) {
                    // do not take Resource into consideration
                    continue;
                }
                if (bean.hasRawTypeDotName(decoratedType.name())) {
                    throw new UnsupportedOperationException("Decorating built-in bean types is not supported! " +
                            "Decorator " + decoratorClass + " is attempting to decorate " + decoratedType.name());
                }
            }
        }

        if (priority == null) {
            if (beanDeployment.strictCompatibility) {
                // decorator without `@Priority` is disabled per the specification
                return null;
            }

            LOGGER.info("The decorator " + decoratorClass + " does not declare any @Priority. " +
                    "It will be assigned a default priority value of 0.");
            priority = 0;
        }

        if (Modifier.isAbstract(decoratorClass.flags())) {
            JandexTypeSystem ts = JandexTypeSystem.of(beanDeployment.getBeanArchiveIndex());

View on GitHub (pinned to e1c734241f)

Solutions

1. Do not decorate built-in types; wrap the usage in your own interface or intercept at your own bean instead.
2. For events, create your own event abstraction/facade and decorate that.
3. Use an observer or explicit wrapper class instead of @Decorator for built-in behavior.
4. Ensure the decorated type's raw type is your application interface, not a javax/jakarta or Arc built-in.

Example fix

// before
@Decorator
public class EventLogger implements Event<Payload> { ... }

// after
public interface PayloadEventDispatcher { void dispatch(Payload p); }
@Decorator
public class EventLogger implements PayloadEventDispatcher { @Delegate PayloadEventDispatcher delegate; }

Set<String> builtins = Set.of("jakarta.enterprise.inject.Instance","jakarta.enterprise.event.Event","jakarta.enterprise.inject.spi.BeanManager");
for (Class<?> itf : decorator.getClass().getInterfaces())
    if (builtins.contains(itf.getName())) throw new IllegalStateException("Cannot decorate built-in type " + itf);

When it happens

Trigger: Writing @Decorator SomeDecorator implements Instance<Foo> or decorating Event/BeanManager/other BuiltinBean raw types; only BuiltinBean.RESOURCE is skipped from the check.

Common situations: Trying to add cross-cutting behavior around Event firing or Instance resolution; misreading the spec that decorators apply only to managed beans; copying a decorator onto a built-in type interface.

Related errors

• Decorated interface ${decoratedType} not found in the index
• Injected @Decorated Bean<> has to use the delegate type as i
• Unable to construct type for ${decorator}: ${e.getMessage()}
• Decorated type not found in the bean archive index: ${decora
• The decorator ${decoratorClass} has no @Delegate injection p

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/f63d458607ae6f30. Report an issue: GitHub.