An error occurred while trying to write to the entity “claims” [id=d150a3cb-49c3

The comment from sayalip helped me in my case. For some reason the "@GeneratedValue" wasn't added to the primary key field in the XSD by Appian, so I added this manually and the error was resolved. 

Thank you ! It helped me.

I got this same error. (Details: org.hibernate.id.IdentifierGenerationException: ids for this class must be manually assigned before calling save())

I had wanted to create my first Appian WEB API.

I created a Data Store Entity without an autogenerated ID field.  

I created a Service Account and got an API key, put the Service account into the viewer group and gave it access to my DSE, per the docs (Creating Web APIs - Appian 21.3)

My primary key(PK) field is unique, and called CNUMBER.

I tried to use the first example example in the

a!writeToDataStoreEntity(
  dataStoreEntity: cons!CES_POINTER_CHECKS_DATASTOREENTITY,
  valueToStore: type!Employee(
    CNUMBER: http!request.queryParameters.CNUMBER,
    CDATE: http!request.queryParameters.CDATE,
    CAMOUNT: http!request.queryParameters.CAMOUNT,
    CDESC: http!request.queryParameters.CDESC
  ),
  onSuccess: a!httpResponse(
    statusCode: 200,
    headers: {
      a!httpHeader(name: "Content-Type", value: "application/json")
    },
    body: a!toJson(
      fv!storedValues
    )
  ),
  onError: a!httpResponse(
    statusCode: 500,
    headers: {
      a!httpHeader(name: "Content-Type", value: "application/json")
    },
    body: a!toJson(
      {
        error: "There was an error writing to the data store"
      }
    )
  )
)

When I tested it in the WEB API node it worked perfectly and added or updated a record in my table.

When I tried to access remotely, I got the error.

I tried adding an auto generated id field, then the WEB API node failed and I still got the error. I would up fixing this by using the Web API Tutorial Level II example:  Web API Tutorial - Level II - Appian 21.3

So the working code is:

a!localVariables(
   local!value: cast(
   'type!{urn:com:appian:types}CES_CHECKS',
    a!fromJson(http!request.body)
    ),
    a!writeToDataStoreEntity(
        dataStoreEntity: cons!CES_POINTER_CHECKS_DATASTOREENTITY,
        valueToStore: local!value,
        onSuccess: a!httpResponse(
        statusCode: 200,
        headers: {
       a!httpHeader(
       name: "Content-Type",
      value: "application/json"
     )
    },
     body: a!toJson(fv!storedValues)
    ),
    onError: a!httpResponse(
    statusCode: 500,
    headers: {
    a!httpHeader(
    name: "Content-Type",
   value: "application/json"
   )
  },
  body: a!toJson(
  {
    error: "There was another error writing to the data store"    
   }
   )
  )
 )

)

Which works great when called from UBUNTU curl as follows:

curl myenv.appian.community/.../myenv_cendpoint -H "Appian-API-Key:MySecretApiKeykjldsjfksjflsjdfsjldsjfkldjslfj" -H "Content-Type:application/json" --request POST --data '{"CNUMBER":12,"CDATE":"20210920","CAMOUNT":2123.44,"CDESC":"a desc"}'

This was a pain to hack out.  Hope this helps someone!

Thanks this help!