Code based Odata CLient Proxy Response handler returns Exception when the response contains null

[aravindhan2529]

hi, 

we are using code based odata client proxy -( rest service ) to send or receive data . i have defined the model class and set the response body structure for the HTTP operation. In the response handler class - /IWBEP/IF_CP_RESPONSE_HANDLER~HANDLE_REST_RESPONSE, it is unable to parse the response to the desired format and getting error /IWBEP/CM_CP-168: Instance of a complex type could not be deserialized. I have defined the response structure fields to be of type string and as nullable. 

Response payload structure: 

[
  {
    "status": 500,
     "id" : null,
    "externalId": null,
"message": "Some string"
  }
]

Some of the fields in the response structure are optional and they are ignored or sent as null by other REST API. Can you please guide what is wrong/missing and how to resolve the error. 

Thanks 

[aravindhan2529]

Hi JyothirAditya, Since the proxy model is already marked as nullable and the same mapping works when those fields contain actual values, I would look more closely at how the generated client proxy handles `null` for those properties. The error `/IWBEP/CM_CP-168` suggests the issue is happening during deserialization of the complex type rather than simply a JSON structure mismatch. It might be worth checking the generated proxy definition and the exact ABAP types used for `id` and `externalId`, especially how their nullable properties are represented. If you can share the generated response structure/model definition for these fields, it would be easier to narrow down where the `null` handling is failing.

[sravan_aleshwaram]

Hello @JyothirAditya_Kundhurthi 

The JSON response does not match the proxy model

For nullable fields, ensure the proxy property is marked nullable. If null handling still fails, ask the REST API to omit null fields or send empty strings.

Then regenerate the OData client proxy/model and retest.

Thanks,
Sravan

[JyothirAditya_Kundhurthi]

its not possible to omit or send empty strings from other system. i have defined the property as nullable, The json response matched the proxy model.This issue arises only when the response is different, for other case able to map the data.