Insert in to join table Spring JPA with Kotlin - kotlin

Question

My entiti of member:
#Entity(name = "Members")
data class Member(
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
val id: Long? = null,
#Column(unique = true)
#Basic
val uid: String,
#Column(unique = true)
#Basic val email: String,
#ManyToMany(fetch = FetchType.LAZY, cascade = [CascadeType.ALL])
#JoinTable(name = "groups_members")
#JsonIgnore
val groups: Collection<Group?> = ArrayList(),
#OneToMany(mappedBy = "member")
#JsonIgnore
val tasks: List<Task?> = ArrayList(),
#OneToMany(mappedBy = "creator")
#JsonIgnore
val createdTasks: List<Task?> = ArrayList(),
#OneToMany(mappedBy = "creator")
#JsonIgnore
val createdMeetings: List<Meeting?> = ArrayList(),
#OneToMany(mappedBy = "creator")
#JsonIgnore
val createdGroups: List<Group?> = ArrayList(),
#ManyToMany(fetch = FetchType.LAZY, cascade = [CascadeType.ALL])
#JoinTable(name = "meetings_members")
#JsonIgnore
val meetings: List<Meeting?> = ArrayList()
)
entity of group of members:
package com.kotlincoders.tmsapi.data
import com.fasterxml.jackson.annotation.JsonIgnore
import javax.persistence.*
#Entity(name = "team")
data class Group(
#Id #GeneratedValue(strategy = GenerationType.IDENTITY) val id: Long? = null,
#Column(unique = true, name = "name")
#Basic
val name: String,
#Basic
val description: String,
#ManyToMany(fetch = FetchType.LAZY, cascade = [CascadeType.ALL], mappedBy = "groups")
#JsonIgnore
val members: List<Member> = ArrayList(),
#OneToMany(mappedBy = "group")
#JsonIgnore
val tasks: List<Task> = ArrayList(),
#JsonIgnore
#ManyToOne val creator: Member
){
override fun toString(): String {
return "Group(id=${this.id},name=${this.name},description=${this.description})"
}
fun addMember(member: Member){
members.plus(member)
member.groups.plus(this)
}
}
Method in controller:
#PostMapping("/add/")
fun add(#RequestBody request: AddGroupRequest) {
val member = memberService.findByUid(request.creatorUid)
var group = Group(name = request.title, creator = member, description = request.description)
group.addMember(member)
groupService.save(group)
}
But when i try add member to group i don't have any exception but nothing is inserted to join table and i don know why.
Groups are added succesfully.
I have the same problem with others entities, and i tryed many ways to solve it and nothing works.

Answer 1

The problem here is related to lazy fetching, to solve that try to use kotlin allOpen plugin (More info in the link at the end of the answer).
Using data classes (with val) with JPA is not the best option, read this quote from spring example:
Here we don’t use data classes with val properties because JPA is not designed to work with immutable classes or the methods generated automatically by data classes. If you are using other Spring Data flavor, most of them are designed to support such constructs so you should use classes like data class User(val login: String, …​) when using Spring Data MongoDB, Spring Data JDBC, etc.
https://github.com/spring-guides/tut-spring-boot-kotlin#persistence-with-jpa