How to add random value in Json Body in Gatling?

I need to create a random positive integer each time and send it to Json body in Gatling.

I used the below code to create a random positive ineger:

val  r = new scala.util.Random;
val OrderRef = r.nextInt(Integer.MAX_VALUE);

but, How can I feed the randomly generated value into the json body?

I tried:

.exec(http("OrderCreation")
.post("/abc/orders")
.body(StringBody("""{    "orderReference": "${OrderRef}"}""").asJson)  

But, this doesn't seem to work. Any clues please.

Thanks!