Kotlin:Collection既没有泛型类型,也没有OneToMany.targetEntity()

Question

我有一个Enum课程 RoleType

public enum RoleType {
    SYSTEM_ADMIN, PROJECT_ADMIN, USER;
}

在我的User实体类中,我为枚举集合提供了以下映射.这是Java代码:

@JsonProperty
@ElementCollection
@Enumerated(EnumType.STRING)
@CollectionTable(name = "user_role", joinColumns = @JoinColumn(name = "user_id"))
private Set<RoleType> roles;

我将此User实体类转换Kotlin为以下代码:

@JsonProperty
@Enumerated(EnumType.STRING)
@ElementCollection
@CollectionTable(name = "user_role", joinColumns = arrayOf(JoinColumn(name = "user_id")))
var roles: kotlin.collections.Set<RoleType>? = null

转换后,hibernate抛出以下异常:

Collection has neither generic type or OneToMany.targetEntity() defined: com.a.b.model.User.roles

它在Java之前运行良好.

我也试过像这样添加targetClassin @ElementCollection:

@ElementCollection(targetClass = RoleType::class)

但它也引发了另一个例外.

Fail to process type argument in a generic declaration. Member : com.a.b.model.User#roles Type: class sun.reflect.generics.reflectiveObjects.WildcardTypeImpl
ERROR [2017-05-27 04:46:33,123] org.hibernate.annotations.common.AssertionFailure: HCANN000002: An assertion failure occurred (this may indicate a bug in Hibernate)
! org.hibernate.annotations.common.AssertionFailure: Fail to process type argument in a generic declaration. Member : com.a.b.model.User#roles Type: class sun.reflect.generics.reflectiveObjects.WildcardTypeImpl

注:如果我改变的修改roles,从var到val,它的工作,但我需要这是一个可变的类型.我不明白一个字段的可变性是如何在hibernate中创建问题的.

注意:我正在使用Kotlin 1.1.2-2和Hibernate 5.2版本.

Answer 1

你试过改变吗？

var roles: Set<RoleType>? = null

至

var roles: MutableSet<RoleType>? = null

如果您查看接口定义Set,您将看到它定义为,public interface Set<out E> : Collection<E>而MutableSet定义为public interface MutableSet<E> : Set<E>, MutableCollection<E>

Set<out E>相信Java的等价物Set<? extends E>而不是你想要的东西Set<E>.