Allow sending fields with null value in create and update batch requests

[JimmyDZH]

Describe the Problem

When we set specific fields to 'null' in our 'create batch' requests, the fields with 'null' values are excluded from the request and are therefore not passed to the SAP system.

SAP allows null values in addition to its initial values with the field annotation "@Semantics.nullValueIndicatorFor:"

With the SDK when we use the following to create an entity with the field "AuszahlungsbetragTatsächlich" and set its value to null explicitly. it seems that the field with the value 'null' is not being sent to the SAP system, which in turn results in the entity being created with an initial value instead of the passed null value.

We encounter the same issue with a put or patch update request. Setting the field spefically to null will set the field to initial.

Is there a way to specifically send the null fields during a create and update batch request?

antrag.setAuszahlungsbetragTatsaechlich(null);
    var createAntragRequest = odataService.createAntrag(antrag);

    try (BatchResponse result =
        odataService.batch().addChangeset(createAntragRequest).execute(destination)) {
 
      Antrag createdAntrag = result.getModificationResult(createAntragRequest).getModifiedEntity();
 
      return sapAntragToEntityMapper.mapAntrag(createdAntrag);
    }

Response after Creation via SDK:

Setting it via postman manually is working as intended:

Request:

Response:

Propose a Solution

It would be helpful to be able to configure the SDK to allow sending of fields with null values, since SAP allows null values.

For example a configuration setting "alwaysSendNullValues" that can be set globally or per request.

Describe Alternatives

No response

Affected Development Phase

Development

Impact

Impaired

Timeline

Go-Live in 1-2 months.

[newtork]

For specific nullable field please try

    var createAntragRequest = odataService.createAntrag(antrag)
+                                         .includingFields(Antrag.AUSZAHLUNGSBETRAG_TATSAECHLICH);

[JimmyDZH]

.includingFields for update does work, for create we get the following error:
Cannot resolve method 'includingFields' in 'CreateRequestBuilder'

[newtork]

Unfortunately I don't see many "good" option with the existing source code.

Our internal implementation for OData v4 in CreateRequestBuilder uses new Gson(). toJson(obj) effectively. Therefore no null values will run.

I think you would need a hack either way.

(1) You could implement your own extension of CreateRequestBuilder (maybe best).

---

(2) Use the generic OData client to send custom JSON payload.

https://sap.github.io/cloud-sdk/docs/java/features/odata/generic-untyped-odata-client

---

(3) Alternatively you customize the entity class.

@RequiredArgsConstructor
@JsonAdapter(NullFieldAntrag.NullFieldAdapter.class)
class NullFieldAntrag extends Antrag
{
    @Delegate
    final Antrag delegate;

    final String nullField;

    public static class NullFieldAdapter extends TypeAdapter<NullFieldAntrag> {
        private static final Gson internal = new Gson();
        private static final Gson internalNull = new GsonBuilder().serializeNulls().create();

        @Override
        public void write(JsonWriter out, NullFieldAntrag wrapper) throws IOException {
            if (wrapper == null || wrapper.delegate == null) {
                out.nullValue();
                return;
            }
            JsonElement tree = internal.toJsonTree(wrapper.delegate);
            JsonObject jsonObject = tree.getAsJsonObject();
            jsonObject.add(wrapper.nullField, JsonNull.INSTANCE);
            internalNull.toJson(jsonObject, out);
        }

        @Override
        public NullFieldAntrag read(JsonReader in) throws IOException {
            throw new UnsupportedOperationException("Read not supported");
        }
    }
}

If you don't want the regular accessors to work on the new class, you can leave out the lombok extension.

such that...

+ antrag = new NullFieldAntrag(antrag, "AuszahlungsbetragTatsaechlich");
  var createAntragRequest = odataService.createAntrag(antrag);

---

(4) Long term solution, you can offer a concrete pull-request to fulfill your actual feature-request.

Currently the SAP Cloud SDK team does not have capacity to implement new features.