注释异常：mappedBy 引用未知目标实体属性

Question

我是 Hibernate 和 JPA 的新手，我正在尝试连接电影、评分者和评级的数据库。我一直收到错误 Caused by: org.hibernate.AnnotationException: mappedBy reference an unknown target entity property: com.stephenalexander.projects.movierecommender.rating.Rating.movie in com.stephenalexander.projects.movierecommender.movie.Movie.ratings。每个 Movie 对象和每个 Rater 对象都与 Rating 具有 OneToMany 关系。这是我写的东西：

评分：

package com.stephenalexander.projects.movierecommender.rating;

import com.stephenalexander.projects.movierecommender.movie.Movie;
import com.stephenalexander.projects.movierecommender.rater.Rater;

import javax.persistence.*;
import java.time.LocalDateTime;
import java.util.Objects;


@Entity
@Table(name="rating")
public class Rating {
    @Column(name = "rating_id")
    private Long ratingId;
    @Column(name = "rating")
    private Double ratingValue;
    private LocalDateTime time;

    @ManyToOne
    @JoinColumn(name = "rater_id", nullable = false)
    private Rater rater;

    @ManyToOne
    @JoinColumn(name = "movie_id", nullable = false)
    private Movie movie;

电影：

package com.stephenalexander.projects.movierecommender.movie;

import com.stephenalexander.projects.movierecommender.rating.Rating;

import javax.persistence.*;
import java.util.List;

@Entity
@Table(name = "movie")
public class Movie {
    @Id
    @GeneratedValue(
            strategy = GenerationType.AUTO
    )

    @Column(name = "movie_id")
    private Integer movieId;
    private String title;
    private int year;
    @Column(name = "posterurl")
    private String posterUrl;
    @Column(name = "runningtime")
    private int runningTime;

    @OneToMany(fetch = FetchType.LAZY, mappedBy = "movie")
    List<Rating> ratings;

评分者：

package com.stephenalexander.projects.movierecommender.rater;

import com.stephenalexander.projects.movierecommender.rating.Rating;

import javax.persistence.*;
import java.util.List;
import java.util.Objects;

@Entity
@Table(name = "rater")
public class Rater {
    @Id
    @GeneratedValue(
            strategy = GenerationType.AUTO
    )
    @Column(name = "rater_id")
    private Long raterId;

    @OneToMany(fetch = FetchType.LAZY, mappedBy = "rater")
    private List<Rating> ratings;

我看过其他一些帖子，这个错误似乎最常见的原因是 mappedBy 注释引用了所有者 class 中实例变量名称以外的其他内容。我相信我做对了，因为 Rating class 有一个名为 rater 的变量和一个名为 movie 的变量。我不确定还有什么可能导致错误。非常感谢阅读！

编辑：在此处的答案中添加我的评论以阐明我认为这些注释是如何工作的：

据我理解，List<Rating> ratings是mappedBy:"movie"，所以Rating中的movie对象通过其注解会告诉你关系在哪一列建立在，它是电影的主键和评分的外键，movie_id。 rater_id 也一样。这不是整个事情的运作方式吗？

编辑 2：我的另一个想法可能是一种误解...如果我已经在我的 psql 数据库中设置了关系，那么这些符号是否不是必需的？这是多余的吗？我认为这些的目的是让我更轻松地浏览 java 中的查询。在我不断尝试编写查询和运行导致错误导致我相信我的代码不知道这些表是相关的之后，我被引导到这些定义关系的符号。以下是它们在 PostgreSQL 中的全部设置方式：

-----------+-----------------------------+-----------+----------+-------------------------------------------
 rating_id | integer                     |           | not null | nextval('rating_rating_id_seq'::regclass)
 rater_id  | integer                     |           | not null |
 movie_id  | integer                     |           | not null |
 rating    | smallint                    |           |          |
 time      | timestamp without time zone |           |          |
Indexes:
    "rating_pkey" PRIMARY KEY, btree (rating_id)
Foreign-key constraints:
    "rating_movie_id_fkey" FOREIGN KEY (movie_id) REFERENCES movie(movie_id) ON UPDATE CASCADE
    "rating_rater_id_fkey" FOREIGN KEY (rater_id) REFERENCES rater(rater_id) ON UPDATE CASCADE

                Table "public.rater"
  Column  |  Type   | Collation | Nullable | Default
----------+---------+-----------+----------+---------
 rater_id | integer |           | not null |
Indexes:
    "rater_pkey" PRIMARY KEY, btree (rater_id)
Referenced by:
    TABLE "rating" CONSTRAINT "rating_rater_id_fkey" FOREIGN KEY (rater_id) REFERENCES rater(rater_id) ON UPDATE CASCADE

                         Table "public.movie"
   Column    |          Type          | Collation | Nullable | Default
-------------+------------------------+-----------+----------+---------
 movie_id    | integer                |           | not null |
 title       | character varying(100) |           | not null |
 year        | smallint               |           | not null |
 runningtime | smallint               |           | not null |
 posterurl   | character varying(350) |           |          |
Indexes:
    "movie_pkey" PRIMARY KEY, btree (movie_id)
Referenced by:
    TABLE "movies_genres" CONSTRAINT "fk_movie" FOREIGN KEY (movie_id) REFERENCES movie(movie_id)
    TABLE "movies_directors" CONSTRAINT "fk_movie" FOREIGN KEY (movie_id) REFERENCES movie(movie_id)
    TABLE "movies_countries" CONSTRAINT "fk_movie" FOREIGN KEY (movie_id) REFERENCES movie(movie_id)
    TABLE "rating" CONSTRAINT "rating_movie_id_fkey" FOREIGN KEY (movie_id) REFERENCES movie(movie_id) ON UPDATE CASCADE

Answer 1

@Column(name = "movie_id")
private Integer movieId;

@ManyToOne
@JoinColumn(name = "movie_id", nullable = false)
private Movie movie;

你在评级和电影中有一个与 movie_id 相同的列。因此有冲突。

改变其中之一。

Answer 2

缺少的是 @OneToMany 的 targetEntity = Rating.class 参数。所以不同类内的函数注解如下：

电影

@OneToMany(fetch = FetchType.LAZY, targetEntity = Rating.class, mappedBy = "movie")
private List<Rating> ratings

评价者

@OneToMany(fetch = FetchType.LAZY, targetEntity = Rating.class, mappedBy = "rater")
private List<Rating> ratings

评分

@ManyToOne
@JoinColumn(name = "rater_id", nullable = false)
private Rater rater;

@ManyToOne
@JoinColumn(name = "movie_id", nullable = false)
private Movie movie;

感谢所有看过这篇文章的人！

注释异常：mappedBy 引用未知目标实体属性

Annotation Exception: mappedBy reference an unknown target entity property

java

spring

annotations

hibernate

jpa

注释异常：mappedBy 引用未知目标实体 属性

Annotation Exception: mappedBy reference an unknown target entity property

java

spring

annotations

hibernate

jpa

注释异常：mappedBy 引用未知目标实体属性