apache/beam · error · IllegalArgumentException

cannot register Coder : method named 'of' with arguments of

Error message

cannot register Coder : method named 'of' with  arguments of Coder type is not accessible

What it means

After signature checks, getFactoryMethod calls setAccessible(true) on the `of` method so it can be invoked reflectively even if package-private or in a restricted package. If a SecurityManager (or similar access control) rejects the setAccessible call, a SecurityException is caught and rethrown as this IllegalArgumentException. Registration fails because the provider cannot guarantee it can invoke the factory.

Source

Thrown at sdks/java/core/src/main/java/org/apache/beam/sdk/coders/CoderProviders.java:148

                + numTypeParameters
                + " arguments of Coder type is not static");
      }
      if (!coderClazz.isAssignableFrom(factoryMethodCandidate.getReturnType())) {
        throw new IllegalArgumentException(
            "cannot register Coder "
                + coderClazz
                + ": "
                + "method named 'of' with "
                + numTypeParameters
                + " arguments of Coder type does not return a "
                + coderClazz);
      }
      try {
        if (!factoryMethodCandidate.isAccessible()) {
          factoryMethodCandidate.setAccessible(true);
        }
      } catch (SecurityException exn) {
        throw new IllegalArgumentException(
            "cannot register Coder "
                + coderClazz
                + ": "
                + "method named 'of' with "
                + numTypeParameters
                + " arguments of Coder type is not accessible",
            exn);
      }

      return factoryMethodCandidate;
    }

    @Override
    public String toString() {
      return MoreObjects.toStringHelper(getClass())
          .add("rawType", rawType)
          .add("factoryMethod", factoryMethod)
          .toString();

View on GitHub (pinned to 12126d8942)

Solutions

1. Make the `of` method `public` in the Coder class so setAccessible is unnecessary
2. If a SecurityManager is active, grant ReflectPermission("suppressAccessChecks") to the Beam codebase in the policy file
3. Avoid cross-module reflection: keep the coder class and its factory in an exported/open module
4. Fall back to CoderProviders.forCoder(typeDescriptor, coderInstance) with a directly constructed coder

Example fix

// before
static <T> MyCoder<T> of(Coder<T> c) { ... }  // package-private
// after
public static <T> MyCoder<T> of(Coder<T> c) { ... }

static boolean ofIsPublic(Class<?> coderClazz) throws NoSuchMethodException {
  Class<?>[] argTypes = new Class<?>[coderClazz.getTypeParameters().length];
  java.util.Arrays.fill(argTypes, Coder.class);
  return java.lang.reflect.Modifier.isPublic(
      coderClazz.getDeclaredMethod("of", argTypes).getModifiers());
}

try {
  CoderProvider provider = CoderProviders.fromStaticMethods(rawType, coderClazz);
} catch (IllegalArgumentException e) {
  if (e.getCause() instanceof SecurityException) {
    throw new IllegalStateException(
        "Grant ReflectPermission('suppressAccessChecks') or make 'of' public", e);
  }
  throw e;
}

When it happens

Trigger: CoderProviders.fromStaticMethods(rawType, coderClazz) where coderClazz's `of` method is non-public (package-private/private) or the class is in another module, and the running JVM has a SecurityManager denying suppressAccessChecks, or strong JPMS encapsulation blocks the access widening.

Common situations: Package-private `of` methods registered from another package; running inside a sandboxed environment (app server, old SecurityManager policy) without ReflectPermission("suppressAccessChecks"); Java 9+ module encapsulation scenarios in combination with security policies.

Understand the failure class

Background: Permission denied / not authorized / 403 Forbidden: access-control rejections when the caller lacks the required role, grant, or ownership — this error's family across 18 libraries.

Related errors

• error when invoking Coder factory method
• cannot register Coder : does not have an accessible method n
• cannot register Coder : method named 'of' with arguments of
• cannot register Coder : method named 'of' with arguments of
• Unable to find UserCodeException.wrap

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/5ca2ba6eade81089. Report an issue: GitHub.