Spring JPA Projection duplicates parent entity when fetching nested collection with JPQL - json

Question

Quick explanation
While fetching a nested collection from a JPQL query it serializes one parent object for each nested object. The intended behavior would be serializing one single parent object with a single collection/set of objects.
Using Spring DATA/DATA REST
JPQ Query
#Query(
"""
select distinct ticketOrder.id as id, user.name as name, ticket as tickets from TicketOrder ticketOrder
inner join User user on user.id = ticketOrder.user.id
inner join Ticket ticket on ticket.ticketOrder.id = ticketOrder.id
where user.uid = :uid
"""
)
fun findByUserUid(uid: UUID, pageable: Pageable): Page<TicketOrderProjection>
Related Entity Classes
TicketOrder
class TicketOrder(
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "order_id", nullable = false)
val id: Long? = null,
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(nullable = false)
val user: User,
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(nullable = false, updatable = false)
val raffle: Raffle? = null,
#OneToMany(mappedBy = "ticketOrder", cascade = [CascadeType.ALL], orphanRemoval = true, fetch = FetchType.LAZY)
var tickets: MutableList<Ticket> = mutableListOf(),
#OneToOne(fetch = FetchType.LAZY)
var transaction: Transaction?,
#CreationTimestamp
#Column(name = "created_at", updatable = false)
val createdAt: Timestamp? = null,
#UpdateTimestamp
#Column(name = "updated_at")
val updatedAt: Timestamp? = null,
#Column(name = "completed_at", nullable = true)
var completedAt: LocalDateTime? = null,
#Column
var checkoutCode: String? = null,
#Enumerated(EnumType.STRING)
#Column(name = "order_status", nullable = false)
var status: TicketOrderStatus
)
/* ... omitted for brevity */
Ticket
#Entity
class Ticket(
#Id
#GeneratedValue(strategy = IDENTITY)
#Column(name = "ticket_id", nullable = false)
val id: Long? = null,
#Column(name = "ticket_number", nullable = false, columnDefinition = "UNIQUE")
val ticketNumber: Int,
#ManyToOne
#JoinColumn
var ticketOrder: TicketOrder? = null,
#ManyToOne
#JoinColumn
var raffle: Raffle
)
User
class User(
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "user_id", nullable = false)
val id: Long? = null,
#Column(nullable = false)
val name: String,
#Column(nullable = false)
val phone: Long,
#Column(nullable = false)
val email: String,
#Column(nullable = false, updatable = false)
val uid: UUID = UUID.randomUUID(),
#CreationTimestamp
#Column(name = "created_at", updatable = false)
val createdAt: Timestamp? = null
)
Projections
TicketOrderProjection
#Projection(types = [TicketOrder::class])
interface TicketOrderProjection {
val id: Long
val name: String
val tickets: Set<TicketsProjection>
}
TicketsProjection
#Projection(types = [Ticket::class])
interface TicketsProjection {
#get:Value("#{target.id}")
val id: Int
}
Finally
Response at RestController
{
"content": [
{
"name": "Raphael Heizer",
"id": 10,
"tickets": [
{
"id": 21
}
]
},
{
"name": "Raphael Heizer",
"id": 10,
"tickets": [
{
"id": 22
}
]
},
{
"name": "Raphael Heizer",
"id": 10,
"tickets": [
{
"id": 23
}
]
}
],
"pageable": {
// omitted
}
Expected response
{
"content": [
{
"name": "Raphael Heizer",
"id": 10,
"tickets": [
{
"id": 21,
},
{
"id": 22
},
{
"id": 23
}
]
},
],
"pageable": {
// omitted
}