How to add another object in JSON with Ktor - json

Question

I'm creating API server with Ktor and using exposed SQL.
I have two tables like below:
/// Performance Table
#kotlinx.serialization.Serializable
data class PerformanceDAO(val performanceId: String, val title: String, val actor: String)
object Performances : Table() {
val performanceId: Column<String> = varchar("performanceId", 20)
val title: Column<String> = varchar("title", 50)
override val primaryKey = PrimaryKey(performanceId)
}
//Actor Table
object Actors: Table() {
val performanceId: Column<String> = reference("performanceId", Performances.performanceId)
val name: Column<String> = varchar("name", 10)
}
and I'm trying to get data this way:
class PerformanceDAOImpl : PerformanceDAOFacade {
private fun resultRowToPerformance(row: ResultRow) = PerformanceDAO(
performanceId = row[Performances.performanceId],
title = row[Performances.title],
actor = row[Actors.name],
)
override suspend fun allPerformances(): List<PerformanceDAO> = dbQuery {
Actors.leftJoin(Performances)
.slice(Actors.name, Performances.title, Performances.performanceId)
.selectAll()
.groupBy(Performances.title).map(::resultRowToPerformance)
}
}
and then I got only one actors without a key.
{
"performanceId": "PF13234",
"title": "Harry footer",
"actor": [
"John"
]
},
but I want get data like this
{
"performanceId": "PF13234",
"title": "Harry footer",
"actor": [
{
"name: "John",
"image": "/upload/images/image.jpg"
},
{
"name: "Harry",
"image": "/upload/images/image.jpg"
},
]
},
I want to know how to make sub object in JSON with Exposed SQL!

Answer 1

You have to create a separate data class ActorDTO and map it in your code by making subquery. Also, I would advice to make Exposed Entities and then map them to your DAO, it can be much simpler but will add some boilerplate code.
Please check documentation