spring - Kotlin Hibernate 中删除 ManyToOne 列表类型

Question

我正在尝试在 Springs 中创建一个简单的 ManyToOne 关系

// City.kt
package com.example.helpme.entity

import javax.persistence.*
import javax.validation.constraints.*

@Entity
data class City(
    @Id id: Int,
    var name: String,
    @ManyToOne(optional = false) state: State
)

// State.kt
package com.example.helpme.entity

import javax.persistence.*
import javax.validation.constraints.*

@Entity
data class State(
    @Id id: Int,
    var name: String,
    @OneToMany cities: Set<City> = emptySet(),
)

但是 Intelij Idea 告诉我 'One To Many' attribute value type should not be '? extends City'

当我尝试运行时，我得到了

org.springframework.beans.factory.BeanCreationException:创建在类路径资源[org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaConfiguration.class]中定义的名为“entityManagerFactory”的bean时出错:调用init方法失败；嵌套异常是 org.hibernate.AnnotationException:Collection 既没有定义泛型类型，也没有定义 OneToMany.targetEntity():com.example.helpme.entity.State.products

Answer 1

将 Set 更改为 MutableSet 对我有用

// State.kt
package com.example.helpme.entity

import javax.persistence.*
import javax.validation.constraints.*

@Entity
data class State(
    @Id id: Int,
    var name: String,
    @OneToMany cities: MutableSet<City> = mutableSetOf(),
)