Java Development Tools

I am using JDeveloper 11.1.1.9.0

I am trying to create a relationship using the URL

http://<RestReourceBaseUrl>

and I have mentioned the Content-Type as application/vnd.oracle.adf.batch+json.

Below is the REST payload.

{
   "parts":[
      {
         "id":"ExistingPG_Add",
         "path":"/parentEntity/100000011628005/child/RelationEntity",
         "operation":"create",
         "payload":[
            {
              "RelEntityId": 100000011628007
            }
         ]
      }
   ]
}

But it is showing the error

Attribute RelEntityId in ParentChildRelationEO is required.

I have provided the mandatory attribute RelEntityId in the REST payload. But still it is showing the error.

Please advise.

Thanks,

Nigel.