JPA@OneToMany不保存父ID

我使用Spring Boot和JPA开发API

{
    "name": "Rice",
    "description": "Lorem ipsum dolor sit amet",
    "variants": [
        {
            "amount": 1,
            "unit": "kg",
            "price": 60000
        }
    ]
}

这是我的模型:

产品.kt

data class Product(
        @Id
        @GeneratedValue
        var id: Long = 0,
        var name: String = "",
        var photo: String = "",
        var description: String = "",

        @OneToMany(mappedBy = "product", cascade = [CascadeType.ALL])
        @JsonBackReference
        var variants: MutableList<Variant> = mutableListOf()
)

@Entity
data class Variant(
        @Id
        @GeneratedValue
        var id: Long = 0,
        var amount: Int = 0,
        var unit: String = "",
        var price: Double = 0.0,

        @ManyToOne(fetch = FetchType.LAZY)
        @JoinColumn(name = "product_id")
        @JsonManagedReference
        var product: Product? = null
)

是否需要应用其他配置? 谢谢你