How to add missing fields to a document?

Kernel
1

I’m trying to do calculations on a document that has computed fields. However the json from which I deserialize the document does not contain all of the calculated fields. While running the computation I get the following exception:

Caused by: com.mgmtp.a12.md.rt.api.ComputationException: Field instance '/Root[1]/PaymentWithInvoice[1]' not found!
        at com.mgmtp.a12.md.internal.rt.ComputationResultImpl.createComputedValue(ComputationResultImpl.java:79)
        at com.mgmtp.a12.md.internal.rt.ComputationResultImpl.<init>(ComputationResultImpl.java:57)
        at com.mgmtp.a12.md.internal.rt.DocumentDynamicRtService.compute(DocumentDynamicRtService.java:96)

How can I add such missing fields to the document before the computation such that I can avoid this exception?

2

I use a document visitor to add those fields:

@RequiredArgsConstructor
public class MissingFieldsAddingDocumentVisitor extends DefaultDocumentVisitor {

	private final DocumentFactory documentFactory;

	@Override
	public VisitProcess visitGroupInstance(GroupInstance groupInstance) {
		Group group = groupInstance.getModelElement();
		Set<Element> existingFields = groupInstance.getChildren().stream().filter(FieldInstance.class::isInstance)
				.map(ElementInstance::getModelElement).collect(Collectors.toSet());
		List<Field> missingFields = group.getElements().stream().filter(Field.class::isInstance).map(Field.class::cast)
				.filter(e -> !existingFields.contains(e)).collect(Collectors.toList());

		if (!missingFields.isEmpty()) {
			missingFields.forEach((field -> documentFactory.createFieldInstance(field, groupInstance)));
		}

		return super.visitGroupInstance(groupInstance);
	}
}

This visitor is used to walk the document and will add missing fields to all previously existing groups of the document.