JPA基于主键建立实体一对一关联报错：referenced property unknown

尝试使用JPA在两个实体间建立一对一关联，但其中一个类出现“referenced property unknown”错误。数据库模型为：appraisal表的vehicle_id列关联到vehicle表的id字段。

相关实体代码如下：

Appraisal类

@Entity
@Table(name = "appraisal")
@Data
@IdClass(AppraisalId.class)
public class Appraisal {
    
    @Id
    @Column(name="vehicle_id")
    private Long vehicleId;
    
    @PrimaryKeyJoinColumn
    @OneToOne(mappedBy = "appraisal")
    private Vehicle vehicle;
    
    @Id
    @Column(name="customer_id")
    private Long customerId;
    
    @OneToOne
    @JoinColumn(name="appraised_for", referencedColumnName="id")
    private Customer customer;
    
    //1列省略
}

AppraisalId类

@Data
public class AppraisalId implements Serializable {
    
    private static final long serialVersionUID = -5373569618334807665L;
    
    private Long vehicleId;
    private Long customerId;

}

Vehicle类

@Entity
@Table(name = "vehicle")
@Getter
@Setter
public class Vehicle {
    
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name="id")
    private Long id;
    
    @OneToOne(mappedBy = "vehicle")
    private Appraisal appraisal;
    
    //其他列省略
}

使用Lombok的@Data注解生成getter和setter，错误信息为：Unknown mappedBy in: ca.allauto.ups.model.Appraisal.vehicle, referenced property unknown: ca.allauto.ups.model.Vehicle.appraisal

你搞反了一对一关联的所有者方和被动方：

• appraisal表通过vehicle_id（作为复合主键的一部分）关联vehicle表，因此Appraisal是关联的所有者方（拥有外键的一方），不需要使用mappedBy属性——mappedBy是给被动方（无外键的一方，也就是Vehicle）用的，用来指定所有者方中维护关联的字段。
• 你在Appraisal的vehicle字段上添加了mappedBy = "appraisal"，这会让JPA去Vehicle类中找名为appraisal的字段来维护关联，但实际上Vehicle里的appraisal字段是用mappedBy = "vehicle"指向Appraisal的vehicle字段，这就导致了循环引用的配置错误。

修改Appraisal类中的vehicle字段配置，去掉mappedBy，并明确@PrimaryKeyJoinColumn的关联字段：

@Entity
@Table(name = "appraisal")
@Data
@IdClass(AppraisalId.class)
public class Appraisal {
    
    @Id
    @Column(name="vehicle_id")
    private Long vehicleId;
    
    @OneToOne
    @PrimaryKeyJoinColumn(name = "vehicle_id", referencedColumnName = "id")
    private Vehicle vehicle;
    
    @Id
    @Column(name="customer_id")
    private Long customerId;
    
    @OneToOne
    @JoinColumn(name="appraised_for", referencedColumnName="id")
    private Customer customer;
    
    //1列省略
}

Vehicle类的配置不需要修改，因为它的@OneToOne(mappedBy = "vehicle")已经正确指向了Appraisal中维护关联的vehicle字段。

这样配置后，JPA就能正确识别关联关系：Appraisal通过主键字段vehicle_id关联Vehicle的主键id，Vehicle通过mappedBy被动关联Appraisal的vehicle字段。

内容的提问来源于stack exchange，提问作者Rob Gravelle