hibernate - InstantiationException:当使Entity字段在Kotlin中不可为空时，没有用于实体的默认构造函数

Question

我有一个项目实体(如下所示)。当我尝试改变

var fullName: String?= null

至:

var fullName: String,

我突然从Hibernate收到InstantiationException:

org.hibernate.InstantiationException: No default constructor for entity:

在此之前，没有任何问题。可能出什么问题了？这是Entity类:

package no.inmeta.ris.project.model.entity

import org.hibernate.annotations.GenericGenerator
import java.util.*
import javax.persistence.*

@Entity
data class Project (

    @Id
    @GeneratedValue(generator = "uuid2")
    @GenericGenerator(name = "uuid2", strategy = "uuid2")
    @Column(columnDefinition = "BINARY(16)")
    var id : UUID? = null,

    var fullName: String,

    var shortName: String? = null,

    var prevRefId: String? = null,

    var startDate: Date? = null,

    var endDate: Date?  = null,

    @ManyToMany(fetch = FetchType.EAGER)
    @JoinTable(name = "Associated_Projects",
        joinColumns = [JoinColumn(name = "associated_project")],
        inverseJoinColumns = [JoinColumn(name = "second_associated_project") ])
    var associatedProjects: List<Project?> = mutableListOf(),

    var shortDescription: String? = null,

    var summary: String?  = null,

    var url: String? = null,

    @ManyToMany(fetch = FetchType.EAGER)
    @JoinTable(name = "Project_Types",
        joinColumns = [JoinColumn(name = "project_id")],
        inverseJoinColumns = [JoinColumn(name = "type_id") ])
    var type: List<Type?> = mutableListOf()
    )

Answer 1

为fullName参数提供默认值或使其可为空。

在您的代码中，它没有默认值，因此在生成的Java字节码中，Project类将没有构造函数而没有参数-它至少需要1个参数才能初始化fullName字段。