OData V4 Edm.Binary Deserialization Fails for Base64URL Payloads returned by odatav4 api

[AlexDiwong]

Describe the Bug

The api to get the binary data for a purchase order returns the data in the OutputBinaryData property as Base64Url encoded, but the sdk expects base64 encoded which fails the deserialization.

Api used:
odata4/sap/api_purchaseorder_2/srvd_a2x/sap/purchaseorder/0001/PurchaseOrder/:id/SAP__self.GetOutputBinaryData()

AI summary of the problem:
odata-v4-core binary deserialization rejects valid Base64URL values for Edm.Binary.

In ODataGenericConverter ODataGenericConverter.java, binary decoding uses Base64.getDecoder() only. If an OData V4 service returns URL-safe Base64 (- and _) in an Edm.Binary field, typed deserialization fails and logs Not deserializable.

This Breaks typed deserialization for services returning Base64URL-encoded binary (for example, S/4HANA GetOutputBinaryData response field OutputBinaryData).

Steps to Reproduce

1. Compile a purchase order service
2. Use the service to GetOutputBinaryData()
3. See deserialisation error when trying to deserialize the response to D_PurOrdGetOutputBinaryDataR.

Expected Behavior

Either the API should conform to returning base64 encoded binaries (which probably would be tricky to roll out), or the sdk needs to correctly treat the OutputBinaryData property to be Base64Url-encoded.

Used Versions

• Java and Maven version via mvn --version: ...
• SAP Cloud SDK version: 5.26.0
• Spring Boot or CAP version: ...

Impact

Inconvenience, We implemented a work around where we get the response raw and manually decode the property.

[newtork]

I take you would like to push for following changes in

cloud-sdk-java/datamodel/odata-v4/odata-v4-core/src/main/java/com/sap/cloud/sdk/datamodel/odatav4/adapter/ODataGenericConverter.java

Lines 55 to 56 in a100c76

	private static final ODataGenericConverter<byte[]> BINARY =
	new ODataGenericConverter<>(byte[].class, Base64.getEncoder()::encodeToString, Base64.getDecoder()::decode);

with...?

    private static final ODataGenericConverter<byte[]> BINARY =
-       new ODataGenericConverter<>(byte[].class, Base64.getEncoder()::encodeToString, Base64.getDecoder()::decode);
+       new ODataGenericConverter<>(byte[].class, Base64.getUrlEncoder().withoutPadding()::encodeToString, Base64.getUrlDecoder()::decode);

[AlexDiwong]

I was looking at doing a PR along those lines, but as far as I can tell it's used for several services, and I'm not sure if this is a bug in the purchase order api or if it's the case for all services.

[AlexDiwong]

Another alternative could be to do base64url as a fallback, but that implies irregularities in the api design which isn't very nice. It would also hide the base64 deserialization error behind a base64url error if it fails both which I also suspect is not the best developer experience.

 @Nonnull
  private static byte[] decodeBinary( @Nonnull final String value )
    {
        try {
            return Base64.getDecoder().decode(value);
        }
        catch( final IllegalArgumentException ignored ) {
            return Base64.getUrlDecoder().decode(value);
        }
    }

[newtork]

Quick update, we're still working on it :)