Kotlin - 数据类实体抛出 StackOverflowError

Question

我尝试将 kotlin（版本 1.2.21）与 spring-boot（1.5.9.RELEASE）结合起来。我在使用带有 @Entity 注释的数据类时遇到了问题。我有问题的实体如下所示：

@Entity
@Table(name = "APP_USER")
data class AppUser(

    @Column(name = "USERNAME", unique = true)
    private val username: String,

    @Column(name = "PASSWORD")
    private val password: String,

    @Column(name = "IS_ACTIVE")
    val isActive: Boolean,

    @Column(name = "REGISTRATION_DATE_TIME")
    val registrationDateTime: LocalDateTime = SystemTimeManager.getSystemDateTime(),

    @OneToMany(mappedBy = "appUser", cascade = [CascadeType.ALL], fetch = FetchType.EAGER)
    val authorities: MutableSet<UserAuthority> = mutableSetOf()
) : EntityBase(), UserDetails {


   internal fun addRole(authority: UserAuthority) {
      this.authorities.add(authority)
   }

}


@Entity
@Table(name = "USER_AUTHORITY")
data class UserAuthority(
    @ManyToOne
    @JoinColumn(name = "APP_USER_ID", nullable = false)
    val appUser: AppUser,

    @Column(name = "ROLE", length = 50, nullable = false)
    @Enumerated(value = EnumType.STRING)
    private val authority: Authority
) : EntityBase(), GrantedAuthority {

override fun getAuthority(): String {
    return authority.name
    }   
}

如您所见，我们在 AppUser 和 UserAuthority 之间有 @OneToMany 关系。现在我尝试添加一些这样的权限：

authoritiesCollection.forEach { appUser.addRole(UserAuthority(appUser, Authority.valueOf(it))) }

在执行期间，第一个权限总是正确地添加到 appUser，但是添加第二个权限会产生 StackOverflowError 和堆栈跟踪

java.lang.StackOverflowError
at security.usermanagement.AppUser.hashCode(AppUser.kt)
at security.usermanagement.UserAuthority.hashCode(UserAuthority.kt)

如果我将这些类设为非数据，它会正常工作。我可能可以通过覆盖 hashcode 和 equals 方法来解决这个问题，但是我有很多实体，所以我真的不想这样做。

Answer 1

AppUser 和 UserAuthority 之间存在循环依赖关系。处理hashCode时需要排除一个来打破循环依赖。

您可以通过将导致循环依赖的属性移动到数据类主体来修复它，这样这些属性就不会在自动生成的字段上使用。在这种情况下，它会将authorities 移动到AppUser 正文：

@Entity
@Table(name = "APP_USER")
data class AppUser(

        @Column(name = "USERNAME", unique = true)
        private val username: String,

        @Column(name = "PASSWORD")
        private val password: String,

        @Column(name = "IS_ACTIVE")
        val isActive: Boolean,

        @Column(name = "REGISTRATION_DATE_TIME")
        val registrationDateTime: LocalDateTime = SystemTimeManager.getSystemDateTime(),

) {
    @OneToMany(mappedBy = "appUser", cascade = [CascadeType.ALL], fetch = FetchType.EAGER)
    val authorities: MutableSet<String> = mutableSetOf()

    internal fun addRole(authority: String) {
        this.authorities.add(authority)
    }

}