Question

我在JPA中有一个实体，我有兴趣转换为枚举。

我面临的问题是我与该表之间存在关系，该关系由联接表映射。

@Entity
@Table(name = "user")
data class User(
    @ManyToMany
    @JoinTable(
        name = "user_certificates",
        joinColumns = [JoinColumn(name = "user_id")],
        inverseJoinColumns = [JoinColumn(name = "certificate_id")]
    )
    var certificates: List<Certficate> = listOf()
)

这是我有兴趣过渡到的枚举，

enum class Certificate(val id: Int) {
  FOO(1),
  BAR(2),
  BAZ(3)
}

是否可以将其转换为具有ID的枚举并使用相同的user_certificates表来存储附加到具有现有关系的实体的枚举？

Answer 1

同一表可以与用户实体类中的以下映射一起使用：

@ElementCollection(fetch = FetchType.EAGER, targetClass = Certificate::class)
@CollectionTable(name = "user_certificates", joinColumns = [JoinColumn(name = "user_id")])
@Column(name = "certificate_id")
@Convert(converter = CertificateEnumConverter::class)
var certificates: List<Certificate> = listOf(),

转换器看起来像

class CertificateEnumConverter : AttributeConverter<Certificate, Int> {
  override fun convertToDatabaseColumn(attribute: Certificate?) = attribute!!.id

  override fun convertToEntityAttribute(dbData: Int?) = Certificate.fromId(dbData!!)
}

如何在JPA中将实体转换为枚举？

1 个答案: