quarkusio/quarkus · error · java.lang.IllegalStateException

Not a resolver:

Error message

Not a resolver: 

What it means

EngineProducer.createResolver loads the class named by quarkus.qute.resolver.<n> class-name config and casts it to io.quarkus.qute.Resolver. If the class loads but does not implement Resolver, startup fails with this error. It guards the reflective instantiation of user-supplied resolvers.

Source

Thrown at extensions/qute/runtime/src/main/java/io/quarkus/qute/runtime/EngineProducer.java:366

    @Produces
    @ApplicationScoped
    Engine getEngine() {
        return engine;
    }

    void onShutdown(@Observes ShutdownEvent event) {
        // Make sure to clear the Qute cache
        Qute.clearCache();
    }

    private Resolver createResolver(String resolverClassName) {
        try {
            Class<?> resolverClazz = Thread.currentThread()
                    .getContextClassLoader().loadClass(resolverClassName);
            if (Resolver.class.isAssignableFrom(resolverClazz)) {
                return (Resolver) resolverClazz.getDeclaredConstructor().newInstance();
            }
            throw new IllegalStateException("Not a resolver: " + resolverClassName);
        } catch (InstantiationException | IllegalAccessException | ClassNotFoundException | IllegalArgumentException
                | InvocationTargetException | NoSuchMethodException | SecurityException e) {
            throw new IllegalStateException("Unable to create resolver: " + resolverClassName, e);
        }
    }

    private TemplateGlobalProvider createGlobalProvider(String initializerClassName) {
        try {
            Class<?> initializerClazz = Thread.currentThread()
                    .getContextClassLoader().loadClass(initializerClassName);
            if (TemplateGlobalProvider.class.isAssignableFrom(initializerClazz)) {
                return (TemplateGlobalProvider) initializerClazz.getDeclaredConstructor().newInstance();
            }
            throw new IllegalStateException("Not a global provider: " + initializerClazz);
        } catch (InstantiationException | IllegalAccessException | ClassNotFoundException | IllegalArgumentException
                | InvocationTargetException | NoSuchMethodException | SecurityException e) {
            throw new IllegalStateException("Unable to create global provider: " + initializerClassName, e);
        }

View on GitHub (pinned to e1c734241f)

Solutions

1. Verify the configured class implements io.quarkus.qute.Resolver and has a public no-arg constructor.
2. Fix the quarkus.qute.resolver.<n>.classes property value to the fully-qualified resolver class.
3. Remove the property if a custom resolver is not actually needed.
4. Check the Quarkus migration guide if the class changed its interface after an upgrade.

Example fix

// before
quarkus.qute.resolver.my-resolver.classes=com.example.MyValueResolver
// after
quarkus.qute.resolver.my-resolver.classes=com.example.MyResolver // implements io.quarkus.qute.Resolver

Class<?> c = Class.forName("com.example.MyResolver");
if (!io.quarkus.qute.Resolver.class.isAssignableFrom(c)) throw new IllegalArgumentException("Not a Resolver");

boolean isResolver(Class<?> c) { return io.quarkus.qute.Resolver.class.isAssignableFrom(c); }

try { app.start(); } catch (IllegalStateException e) { if (e.getMessage().startsWith("Not a resolver")) { /* fix quarkus.qute.resolver config */ } else throw e; }

When it happens

Trigger: Setting a quarkus.qute.resolver.*.classes property to a class that exists on the classpath but does not implement io.quarkus.qute.Resolver (e.g. a ValueResolver or SectionHelper was configured by mistake).

Common situations: Copy-pasting config between resolver/global-provider properties; configuring a class from an internal or wrong package; a library class that stopped implementing Resolver after a Quarkus version upgrade.

Related errors

• Unable to create resolver:
• Not a global provider:
• Unable to create global provider:
• Unable to create instance of Logging Filter ''
• The <clazz.getSimpleName()> class [<instanceClass>] could no

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/f2d9d6893e152c6c. Report an issue: GitHub.