apache/beam · error · java.lang.RuntimeException

Failed to set field to proto. field

Error message

Failed to set field to proto. field:%s

What it means

ToProtoSetter.setToProto writes a Beam field value into a proto Message builder via reflection-like fieldDescriptor.setField. Any RuntimeException during convert or setField is rethrown as a RuntimeException naming the proto field, preserving the underlying cause.

Solutions

1. Inspect e.getCause() for the actual conversion error
2. Align the Beam schema field types with the proto field types and rebuild the converter
3. Check null handling: the setter skips null beamFieldValue, so errors mean a non-null value failed conversion
4. Regenerate schemas after proto changes so descriptors match

Example fix

// before
// Beam row field 'count' is STRING, proto field int64 -> setField throws
// after
// make Beam schema type match proto: use INT64 for 'count' (or STRING int64 in proto)

// check Beam schema type matches proto field type before converting
if (!beamField.getType().getTypeName().toString().equals(ProtoCatalog.getBeamTypeFromFieldType(fieldDescriptor).getTypeName().toString())) throw new IllegalStateException("type mismatch on " + fieldDescriptor.getName());

try { setter.setToProto(builder, beamType, value); } catch (RuntimeException e) { throw new IllegalStateException("field " + e.getMessage() + " cause: " + e.getCause(), e); }

When it happens

Trigger: Building a proto Message from a Beam Row when the Beam field value cannot be converted to the proto field type or setField rejects the value (wrong class, repeated field misuse, descriptor mismatch).

Common situations: Beam schema field type drifts from the proto (e.g. Beam STRING vs proto int64); nullability mismatch; stale schema after proto regeneration; passing a Message built from a different descriptor set.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

• Failed to get field from proto. field
• Failed to get oneof from proto. oneof
• Failed to set oneof to proto. oneof
• bad type: , want
• base64 decode for failed

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/a63d72756779c2f2. Report an issue: GitHub.

Appendix: source

Thrown at sdks/java/extensions/protobuf/src/main/java/org/apache/beam/sdk/extensions/protobuf/ProtoBeamConverter.java:538

    private final Descriptors.FieldDescriptor fieldDescriptor;
    private final BeamToProtoConverter<BeamT, ProtoT> converter;

    ToProtoFieldSetter(Descriptors.FieldDescriptor fieldDescriptor) {
      this.fieldDescriptor = fieldDescriptor;
      this.converter =
          (BeamToProtoConverter<BeamT, ProtoT>) createBeamToProtoConverter(fieldDescriptor);
    }

    @Override
    public void setToProto(
        Message.Builder message, Schema.FieldType fieldType, @Nullable BeamT beamFieldValue) {
      try {
        if (beamFieldValue != null) {
          ProtoT protoValue = converter.convert(beamFieldValue);
          message.setField(fieldDescriptor, protoValue);
        }
      } catch (RuntimeException e) {
        throw new RuntimeException(
            String.format("Failed to set field to proto. field:%s", fieldDescriptor.getName()), e);
      }
    }
  }

  static class ToProtoOneOfSetter implements ToProtoSetter<OneOfType.@Nullable Value> {
    private final Descriptors.OneofDescriptor oneofDescriptor;
    private final Map<String, ToProtoFieldSetter<Object, Object>> protoSetters;

    ToProtoOneOfSetter(Descriptors.OneofDescriptor oneofDescriptor) {
      this.oneofDescriptor = oneofDescriptor;
      this.protoSetters = createConverters(oneofDescriptor.getFields());
    }

    private static Map<String, ToProtoFieldSetter<Object, Object>> createConverters(
        List<Descriptors.FieldDescriptor> fieldDescriptors) {
      Map<String, ToProtoFieldSetter<Object, Object>> converters = new LinkedHashMap<>();
      for (Descriptors.FieldDescriptor fieldDescriptor : fieldDescriptors) {

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