Question

我正在尝试将Kotlin与JPA一起使用，并且基本上得到了两个应该一起工作的类。我在如何使数据类作物可序列化方面遇到问题。我尝试将@Serializable添加到Crops，但是IntelliJ告诉我Crops没有构造函数。这是两个类：

@Entity
data class Crops(
    val amountOwned: Int = 0
) {

@Id
@ManyToOne(fetch = FetchType.EAGER)
lateinit var user: User


@ManyToOne(fetch = FetchType.EAGER)
lateinit var plant: Plant


constructor(user: User, plant: Plant) : this() {
    this.plant = plant
    this.user = user
}}


@Entity
data class User (
    @Id
    val username: String = "",

    @get: NotBlank
    val password: String = "",

    @get: NotBlank
    val salt: String = "",

    @OneToMany(mappedBy = "user")
    val crops: MutableSet<Crops> = HashSet()

已申请所有帮助！谢谢：）

Answer 1

您必须为作物创建一个IdClass，因为JPA需要为诸如EntityManager.find（）之类的方法创建一个类。

data class CropsId (val username: String = "")

然后将其与@IdClass一起使用

@IdClass(CropsPK::class)
@Entity
data class Crops(
    val amountOwned: Int = 0
) {

@Id
@ManyToOne(fetch = FetchType.EAGER)
lateinit var user: User


@ManyToOne(fetch = FetchType.EAGER)
lateinit var plant: Plant


constructor(user: User, plant: Plant) : this() {
    this.plant = plant
    this.user = user
}}

Composite-id类必须实现Serializable

1 个答案: