gradle/gradle · error · IllegalArgumentException

Unable to create an instance of type %s

Error message

Unable to create an instance of type %s

What it means

ManagedObjectFactory.newInstance(owner, propertyName, type, paramType) is invoked from generated managed-property code to materialize a parameterized managed value (for example the element type of a collection property). It delegates to the ManagedObjectRegistry; when no registered @ManagedObjectCreator factory can produce the (type, paramType) pair, the registry returns null and this IllegalArgumentException with the class name is thrown.

Source

Thrown at platforms/core-configuration/model-core/src/main/java/org/gradle/internal/instantiation/generator/ManagedObjectFactory.java:88

        roleHandler.applyRoleTo(owner, value);
    }

    // Called from generated code
    public Object newInstance(ModelObject owner, String propertyName, Class<?> type) {
        Object providedType = getManagedObjectRegistry().newInstance(type);
        if (providedType != null) {
            return attachOwner(providedType, owner, propertyName);
        }
        return attachOwner(instantiator.newInstanceWithDisplayName(type, displayNameFor(owner, propertyName)), owner, propertyName);
    }

    // Called from generated code
    public Object newInstance(ModelObject owner, String propertyName, Class<?> type, Class<?> paramType) {
        Object providedType = getManagedObjectRegistry().newInstance(type, paramType);
        if (providedType != null) {
            return attachOwner(providedType, owner, propertyName);
        }
        throw new IllegalArgumentException("Unable to create an instance of type " + type.getName());
    }

    // Called from generated code
    public Object newInstance(ModelObject owner, String propertyName, Class<?> type, Class<?> keyType, Class<?> valueType) {
        Object providedType = getManagedObjectRegistry().newInstance(type, keyType, valueType);
        if (providedType != null) {
            return attachOwner(providedType, owner, propertyName);
        }
        throw new IllegalArgumentException("Unable to create an instance of type " + type.getName());
    }

    private static ManagedPropertyName displayNameFor(ModelObject owner, String propertyName) {
        if (owner.getModelIdentityDisplayName() instanceof ManagedPropertyName) {
            ManagedPropertyName root = (ManagedPropertyName) owner.getModelIdentityDisplayName();
            return new NestedManagedPropertyName(root, propertyName);
        } else {
            return new RootManagedPropertyName(cachedOwnerDisplayNameOf(owner), propertyName);
        }

View on GitHub (pinned to 534f27719b)

Solutions

1. Register an @ManagedObjectProvider service with an @ManagedObjectCreator method that creates CustomType.
2. Declare the element as a managed (abstract) type in the plugin's managed schema so built-in factories apply.
3. Check the paramType: built-ins cover collections of managed and standard types; custom parameterizations need explicit creators.

Example fix

// before
// managed property: List<CustomType> getRules(); — no provider registered for CustomType
// after
@ManagedObjectProvider
public class CustomTypesProvider {
    @ManagedObjectCreator
    public CustomType create(Class<CustomType> type) { return schema.newInstance(type); }
}

if (managedObjectRegistry.newInstance(type, paramType) == null) {
    throw new IllegalStateException(
        "no @ManagedObjectCreator for " + type.getName() + "<" + paramType.getName() + ">");
}

When it happens

Trigger: A managed schema property such as List<CustomType> where CustomType has no registered creator: generated code calls this method, getManagedObjectRegistry().newInstance(type, paramType) returns null, and the exception fires.

Common situations: Adding new managed types to a software-model plugin without registering their @ManagedObjectProvider; using an arbitrary concrete class where the model requires a managed (abstract) type; parameterizing collections with unmanaged element types.

Related errors

• Could not create an instance of type %s.
• Service %s annotated with @ManagedObjectProvider must have a
• Method %s annotated with @ManagedObjectCreator must not be s
• Invalid %s: %s
• Component '{name}' not found.

AI-assisted analysis of gradle/gradle@534f27719b (2026-08-22). Data as JSON: /api/errors/2a7d60d93f268543. Report an issue: GitHub.