# Incomprehensible type issue =\> why the hell "required: io.gatling.core.session.Session" ???
**URL:** https://community.gatling.io/t/incomprehensible-type-issue-why-the-hell-required-io-gatling-core-session-session/5377
**Category:** Gatling (Open-Source)
**Created:** [November 27, 2019, 2:39pm UTC](https://community.gatling.io/t/incomprehensible-type-issue-why-the-hell-required-io-gatling-core-session-session/5377 "2019-11-27T14:39:51Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@Nicolas\_Delucinge](https://community.gatling.io/u/Nicolas_Delucinge)
#### Post date: [November 27, 2019, 2:39pm UTC](https://community.gatling.io/t/incomprehensible-type-issue-why-the-hell-required-io-gatling-core-session-session/5377/1 "2019-11-27T14:39:51Z")
Hello everybody
I am using following “pure Scala” function within my scenario
def extractCharacteristicFromConfig(config:String, numChar:Int): String = {
val jsonObject: JsValue = Json.parse(config)
//println("==\> DEBUG : config=" +config +" - numChar=" +numChar)
return Json.stringify(jsonObject(numChar))
}
and when i am doing my mvn:gatling test I got this kind of issue from ZincCompiler
found : Int
required: io.gatling.core.session.Session
return Json.stringify(jsonObject(numChar))
^
15:29:30.711 [ERROR] i.g.c.ZincCompiler$ - one error found
15:29:30.718 [ERROR] i.g.c.ZincCompiler$ - Compilation crashed
I am 100% sure than input parameters (config & numChar) are correctly set thanks to the previous DEBUG println
I really dont get the reason of this type mistmatch issue (even if I am pretty sure it is an obvious one for Gatling experts 🙂 )
Thanks in advance for any suggestion!!
For your information here is the overall call chain:
val sc\_scenario\_1\_loop = scenario(Prefix + " - S&C loop")
.exec(SC\_Execution\_Chain())
def SC\_Execution\_Chain() =
exec(
session =\> {
val conf = dataGen.getRandomConfiguration(“c:/TEMP/configurations.json”)
// lets create 3 session variables to store information required to manage PUT /…/characteritics requests
session.set(“randomConfig”, (conf \ “configuration”).get)
.set(“configCharacteristics”, (conf \ “characteristics”).get)
.set(“nbConfigCharacteristics”, (conf \ “characteristics” \ “id”).size)
}
)
// start a new product configuration
.exec(postConfiguration())
.exec(
session =\> {
session.set(“scEncodedConfigurationId”, percentEncoding(session(“scConfigurationId”).as[String]))
}
)
// for i from 1 to nbConfigCharacteristics do
.repeat(session =\> session(“nbConfigCharacteristics”).as[Int], “i”) {
exec(
session =\> {
session.set(“characteristicSetting”, extractCharacteristicFromConfig(session(“configCharacteristics”).as[String], session(“i”).as[Int]))
}
)
.exec(putConfigurationCharacteristics("${scEncodedConfigurationId}", “${characteristicSetting}”))
}
// get the from a complete JSON configuration (=[{characteristic}, …, {characteristic}])
def extractCharacteristicFromConfig(config:String, numChar:Int): String = {
val jsonObject: JsValue = Json.parse(config)
//println("==\> DEBUG : config=" +config +" - numChar=" +numChar +" - char=" +Json.stringify(jsonObject(numChar)))
return Json.stringify(jsonObject(numChar))
}
---
### Author:  [@slandelle](https://community.gatling.io/u/slandelle)
#### Post date: [November 27, 2019, 2:59pm UTC](https://community.gatling.io/t/incomprehensible-type-issue-why-the-hell-required-io-gatling-core-session-session/5377/2 "2019-11-27T14:59:59Z")
Please mind your language here. Some people will find “why the hell” offensive.
I don’t know what your JsValue is (Play?) but it looks like it doesn’t have an apply method so you can’t call jsonObject(Int).
---
### Author:  [@Nicolas\_Delucinge](https://community.gatling.io/u/Nicolas_Delucinge)
#### Post date: [November 27, 2019, 4:37pm UTC](https://community.gatling.io/t/incomprehensible-type-issue-why-the-hell-required-io-gatling-core-session-session/5377/3 "2019-11-27T16:37:40Z")
Hi Stephane
Very sorry for the “why the hell” - I did not want to offend anyone
Indeed JsValue comes from JSON Play framework.
To be sure I tested the content of the extractCharacteristicFromConfig is a “pure Scala context” (using below piece of code)
import play.api.libs.json.\_
val numChar:Int = 2
val config:String =
“”"
> [
> {“id”:“T\_RATED\_CURRENT”,“bomPath”:“00000010”,“value”:“50\_A”},
> {“id”:“T\_POLES\_DESCRIPTION”,“bomPath”:“00000010”,“value”:“4P”},
> {“id”:“TC\_CONNECTIONS”,“bomPath”:“0000”,“value”:“COMPRESSION\_LUG”}
> ]
> “”"
> val jsonObject: JsValue = Json.parse(config)
> println(“Debug: config=” +config +" - numChar=" +numChar +" - char=" +jsonObject(numChar))
> println("Debug : " +Json.stringify(jsonObject(numChar)))
==\> It works fine
What confuse me is the required: io.gatling.core.session.Session error message that makes me think that I am using “badly” Gatling and I dont get why…
---
### Author:  [@slandelle](https://community.gatling.io/u/slandelle)
#### Post date: [November 27, 2019, 5:01pm UTC](https://community.gatling.io/t/incomprehensible-type-issue-why-the-hell-required-io-gatling-core-session-session/5377/4 "2019-11-27T17:01:13Z")
Your problem is that both play-json and Gatling provide implicit conversions with similar signature and they clash with each other.
You have 2 solutions:
- move play-json code to its own classes where you don’t import Gatling components
- make play-json conversions explicit: Json.stringify(JsValue.jsValueToJsLookup(jsonObject)(numChar))