如何在Kotlin中的委托属性上放置JPA注释？

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

plasmic\u reference

join表中的每个条目，这些属性都不能为null。（事实上，数据库强制执行此操作。）

我怎么能告诉科特林

一种简单的方法是尝试使用

lateinit

@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
}

这甚至不编译

在基元类型的属性上不允许使用“lateinit”修饰符

好的，让我们使用建议的解决方案并转换为使用代理

@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>()
}

aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa我没有主意了

---

如何解决此问题？

将其移动到构造函数定义应该可以解决此问题

@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
)

---

不，恐怕不行：“org.eclipse.persistence.exceptions.DescriptorException异常描述：实例创建方法[com.[…].plasmedreference.]，没有参数，不存在或不可访问。”异常表示类中没有arg构造函数。Hibernate不需要arg构造函数即可工作。它是Java框架，所以当我们想将它与kotlin一起使用时，我们需要使用一些插件。。。瞧，我想这些早在很久以前就已经很活跃了，但我们只有

kotlin noarg

而不是

kotlin jpa

。-非常感谢。

@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)

@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
)