如何在Kotlin中对委托属性进行JPA注释？

Question

假设我有一个JPA实体，比如

@Entity
@Table(name = "plasmid_reference")
class PlasmidReference {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    var id: Int? = null

    @Column(name = "project_id")
    var projectId: Int? = null

    @Column(name = "plasmid_id")
    var plasmidId: Int? = null
}

现在，我知道对于plasmid_reference联接表中的每一个条目，这些属性都不能为空。（事实上，数据库强制执行此操作。）

@Entity
@Table(name = "plasmid_reference")
class PlasmidReference {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    lateinit var id: Int

    @Column(name = "project_id")
    lateinit var projectId: Int

    @Column(name = "plasmid_id")
    lateinit var plasmidId: Int
}

好吧，让我们使用建议的解决方案，并转换为使用委托。

@Entity
@Table(name = "plasmid_reference")
class PlasmidReference {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    var id by notNull<Int>()

    @Column(name = "project_id")
    var projectId by notNull<Int>()

    @Column(name = "plasmid_id")
    var plasmidId by notNull<Int>()
}

这仍然不能编译，因为

此批注不适用于目标“带有委托的成员属性”

@Entity
@Table(name = "plasmid_reference")
class PlasmidReference {

    @field:Id
    @field:GeneratedValue(strategy = GenerationType.IDENTITY)
    var id by notNull<Int>()

    @field:Column(name = "project_id")
    var projectId by notNull<Int>()

    @field:Column(name = "plasmid_id")
    var plasmidId by notNull<Int>()
}

@Entity
@Table(name = "plasmid_reference")
class PlasmidReference {

    @delegate:Id
    @delegate:GeneratedValue(strategy = GenerationType.IDENTITY)
    var id by notNull<Int>()

    @delegate:Column(name = "project_id")
    var projectId by notNull<Int>()

    @delegate:Column(name = "plasmid_id")
    var plasmidId by notNull<Int>()
}

The attribute [plasmidId] is not present in the managed type [EntityTypeImpl@960932033:PlasmidReference 
[ javaType: class com.[...].PlasmidReference descriptor: RelationalDescriptor(com.[...].PlasmidReference --> [DatabaseTable(plasmid_reference)]), mappings: 3]].
    at org.eclipse.persistence.internal.jpa.metamodel.ManagedTypeImpl.getAttribute(ManagedTypeImpl.java:151)
    at org.springframework.data.jpa.repository.query.QueryUtils.toExpressionRecursively(QueryUtils.java:635)

我如何解决这个问题？

Answer 1

将其移动到构造函数定义中应该可以做到这一点

@Entity
@Table(name = "plasmid_reference")
class PlasmidReference(
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    var id: Int? = null,
    @Column(name = "project_id")
    var projectId: Int,
    @Column(name = "plasmid_id")
    var plasmidId: Int
)