如何在Gatling中动态生成JSon？

import io.gatling.core.Predef._
import io.gatling.http.Predef._
import io.gatling.jsonpath.JsonPath

class MySimulation extends Simulation {

  val httpConf = http.baseUrl("http://example.com")

  val scn = scenario("My Scenario")
    .exec { session =>
      val dynamicValue = "some dynamic value"
      val jsonBody = s"""{"key": "$dynamicValue"}"""
      session.set("jsonBody", jsonBody)
    }
    .exec(http("My Request")
      .post("/api/endpoint")
      .body(StringBody("${jsonBody}")).asJson
      .check(jsonPath("$.result").is("success")))

  setUp(scn.inject(atOnceUsers(1))).protocols(httpConf)
}