How to join by custom properties

[nonamemanah]

Hello! I need your help.
I have two topics. There is json content in each topics. I need merge messages by unique property in json.
For example:
First json customer:

{
  "customer_id":  102,
  "first_name": "noname",
  "age": 38
}

second json:

{
  "order_id": 1,
  "custId": 102
}

I don't using any dto in my code. Can use JsonObject. I need usage custom properties customer_id and custId as relation properties for merge. Result message will be send to third topic if first and second messages linked by this properties How can I usage this two properties as relation keys?
Thx!

[LGouellec]

Hi @nonamemanah ,

I don't know if you solved this issue, but you probably have to change the key in your topology like this sample :

var stream1 = builder.Stream<String, Customer>("customers"); // key is customerId
var stream2 = builder.Stream<String, Order>("orders"); // key is orderId

stream2
.SelectKey((k,v) => v.CustId)
.Join(stream1, (order, customer) => .... );

Hope it's help