I have the following mapping with a n to n table with composite key:

@Entity
class Reader {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    var id:Long?=null
    
    @OneToMany(mappedBy="reader")
    val readings=mutableListOf()

    @OneToOne
    var bestReading:Reading=...

}

@Entity
class Book {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    var id:Long?=null
    
    @OneToMany(mappedBy="book")
    val readings=mutableListOf()
}

@Entity
@IdClass(Reading.Id::class)
class Reading(

    @Id
    @ManyToOne
    val book:Book,

    @Id
    @ManyToOne
    val reader:Reader
) {
    data class Id(val book:Book,val reader:Reader) : Serializable
    var comment:String=""
}

I want the 'bestReading' relation of Reader to use just the primary key of reader (id) and a book_id field which is both the primary key of the Book and the book_id of the Reading. Is it possible and how?