java - 一对多 SQL 关系

Question

我希望与 SQL 建立 OneToMany 关系，以及 ManyToOne 关系。我有一个 Ticket 实体和一个 TeamMember 实体。但是，当我第一次保存 Ticket 实体时，我不会知道 TeamMember，如果我将其设置为 null，我会得到以下结果:

2020-05-29 23:49:55.754  
ERROR 24020 --- [onPool-worker-2]  o.h.engine.jdbc.spi.SqlExceptionHelper:  
Column 'team_member_id' cannot be null

我应该做什么？

门票:

data class Ticket(
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    var id:Long = 0,
    val ticketId:String,
    var price:Int? = null,
    val openDate:LocalDateTime = LocalDateTime.now(),
    var closeDate:LocalDateTime? = null,
    var paypalId:String? = null,
    var paid:Boolean = false,
    var status:TicketStatus = TicketStatus.OPEN,
    @ManyToOne(fetch = FetchType.EAGER)
    @JoinColumn(name = "team_member_id", nullable = false)
    val teamMember: TeamMember? = null,
    @ManyToOne(fetch = FetchType.EAGER)
    @JoinColumn(name = "customer_id", nullable = false)
    val customer:Customer
)

团队成员:

@Entity
data class TeamMember(
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    var id:Long = 0,
    val discordId:String,
    val joinDate:LocalDateTime,
    val ordersCompleted:Int,
    val amountMade:Int,
    val email:String,
    val pastWork:String,
    @OneToMany(mappedBy = "teamMember", cascade = [CascadeType.ALL],
            orphanRemoval = true, fetch = FetchType.EAGER)
    val tickets:Set<Ticket> = setOf()
)

Answer 1

查看这部分代码(Ticket):

@JoinColumn(name = "team_member_id", nullable = false)
val teamMember: TeamMember? = null

您可以使用 nullable=false 将 SQL 列设置为非 null。

但是，您将该属性声明为 TeamMember? 并将其设置为 null。

您可以在持久化之前将 teamMember 设置为非 null 的值，或者将 nullable 设置为 true (取决于您的需要)。