quarkusio/quarkus · error · DefinitionException

Disposer method must not have an @ObservesAsync parameter (a

Error message

Disposer method must not have an @ObservesAsync parameter (alternatively, async observer method must not have a @Disposes parameter): 

What it means

Build-time CDI definition error from Injection.forDisposer: the method declares more than one parameter annotated @Disposes. Exactly one disposed parameter is allowed per disposer method; the method signature follows the message.

Source

Thrown at independent-projects/arc/processor/src/main/java/io/quarkus/arc/processor/Injection.java:419

    static Injection forDisposer(MethodInfo disposerMethod, ClassInfo beanClass, BeanDeployment beanDeployment,
            InjectionPointModifier transformer) {
        if (beanDeployment.hasAnnotation(disposerMethod, DotNames.INJECT)) {
            throw new DefinitionException("Disposer method must not be annotated @Inject "
                    + "(alternatively, initializer method must not have a @Disposes parameter): "
                    + disposerMethod);
        }
        if (beanDeployment.hasAnnotation(disposerMethod, DotNames.PRODUCES)) {
            throw new DefinitionException("Disposer method must not be annotated @Produces "
                    + "(alternatively, producer method must not have a @Disposes parameter): "
                    + disposerMethod);
        }
        if (Annotations.hasParameterAnnotation(beanDeployment, disposerMethod, DotNames.OBSERVES)) {
            throw new DefinitionException("Disposer method must not have an @Observes parameter "
                    + "(alternatively, observer method must not have a @Disposes parameter): "
                    + disposerMethod);
        }
        if (Annotations.hasParameterAnnotation(beanDeployment, disposerMethod, DotNames.OBSERVES_ASYNC)) {
            throw new DefinitionException("Disposer method must not have an @ObservesAsync parameter "
                    + "(alternatively, async observer method must not have a @Disposes parameter): "
                    + disposerMethod);
        }
        if (Annotations.getParameterAnnotations(beanDeployment, disposerMethod)
                .stream()
                .filter(it -> DotNames.DISPOSES.equals(it.name()))
                .count() > 1) {
            throw new DefinitionException("Disposer method must not have more than 1 @Disposes parameter: "
                    + disposerMethod);
        }

        Injection injection = new Injection(disposerMethod,
                InjectionPointInfo.fromMethod(disposerMethod, beanClass, beanDeployment,
                        (annotations, position) -> annotations.stream().anyMatch(a -> a.name().equals(DotNames.DISPOSES)),
                        transformer));
        injection.injectionPoints.forEach(ipi -> validateInjections(ipi, BeanType.MANAGED_BEAN));
        return injection;
    }

View on GitHub (pinned to e1c734241f)

Solutions

1. Split into two methods: one @ObservesAsync observer, one disposer with @Disposes
2. Remove the @ObservesAsync parameter from the disposer
3. Remove the @Disposes parameter if the method was meant to be an async observer

Example fix

// before
void both(@ObservesAsync Ev e, @Disposes Widget w) {}
// after
void observe(@ObservesAsync Ev e) {}
void dispose(@Disposes Widget w) {}

for (Method m : MyClass.class.getDeclaredMethods()) {
    var names = java.util.Arrays.stream(m.getParameterAnnotations()).flatMap(java.util.Arrays::stream)
        .map(a -> a.annotationType().getSimpleName()).collect(java.util.stream.Collectors.toSet());
    if (names.contains("Disposes") && names.contains("ObservesAsync")) throw new IllegalStateException("Async observer+disposer: " + m);
}

When it happens

Trigger: Declaring a method with both a @Disposes parameter and an @ObservesAsync parameter; detected in Injection.forDisposer.

Common situations: Combining async event handling with disposal in one method; refactoring observers into disposers or vice versa.

Related errors

• Disposer method must not have an @Observes parameter (altern
• Decorator declares an async observer method: ${decoratorClas
• Multiple disposed parameters found for ${disposerMethod}
• Producer method must not have an @ObservesAsync parameter (a
• Disposer method must not be annotated @Inject (alternatively

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/453b8cc39480beac. Report an issue: GitHub.