Ktor handle empty response for arrays - kotlin

Question

I have recently started using Ktor and got stuck at the very beginning itself.
I have a very simple response, which could have content like below -
{
"result": true,
"data": [
{
"Name": "Danish",
"Credit": "80"
},
{
"Name": "Kumar",
"Credit": "310"
}
]
}
Or it could be like this -
{
"result": false,
"data": [],
"message": "No data available, use default user",
"default": [
{
"Name": "Default User",
"Credit": "100"
}
]
}
And my response class is like -
#Serializable
data class UserResponse(
#SerialName("result") var result: Boolean? = null,
#SerialName("data") var data: ArrayList<User?>? = null,
#SerialName("message") var message: String? = null,
#SerialName("default") var default: ArrayList<User?>? = null
)
#Serializable
data class UserResponse(
#SerialName("Name") var name: String? = null,
#SerialName("Credit") var credit: String? = null,
)
io.ktor.client.call.NoTransformationFoundException: No transformation found: class io.ktor.utils.io.ByteBufferChannel
And I am getting NoTransformationFoundException, I think it could be due to data object being empty, but how to fix this?
According to this, we can catch this exception, but I can't use this as I need other data to be used.

Answer 1

Exception looks like you haven't install Json content negotiation plugin, when creating ktor client. It should be like this:
val httpClient = HttpClient {
install(ContentNegotiation) {
json()
}
}
Then you can use this client like this:
val response: UserResponse = httpClient.get("URL").body()