在 Spring Boot JPA 中以多对多关系访问@JoinTable

Question

我创建了一个 API，其中包含演员、电影和类别实体。演员和电影通过映射到名为 movie_actor 的连接 table 的多对多关系连接，类别通过一对多关系与电影连接。

我正在尝试编写一个本机查询，该查询 return 是一个整数，表示来自特定演员播放过的特定类别的电影数量，例如查询将 return 2如果演员出演了 2 部不同的科幻电影。从数据库级别执行此操作没有问题，我可以看到连接 table movie_actor 但是 table 在我的 api 中仍然无法访问，因为它不是一个单独的实体。我如何创建它以自动将演员和电影 ID 映射为 movie_actor table？

这是一个在 H2 数据库中适用于我的示例代码：

SELECT COUNT(*) FROM MOVIE M JOIN MOVIE_ACTOR MA on M.MOVIE_ID = MA.MOVIE_ID WHERE ACTOR_ID = 1 AND CATEGORY_ID = 1

这是我的实体：

演员：

@Entity
@Data
@Table(name = "actor")
@AllArgsConstructor
@NoArgsConstructor
public class Actor {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "actor_id")
private long actorId;

@Column(name = "name")
private String name;

@Column(name = "surname")
private String surname;

@Nullable
@ManyToMany(mappedBy = "actors", fetch = FetchType.EAGER)
@JsonBackReference
private List<Movie> movies = new ArrayList<>();

public Actor(String name, String surname){
    this.name = name;
    this.surname = surname;
}
}

电影：

@Entity
@Data
@Table(name = "movie")
@AllArgsConstructor
@NoArgsConstructor
public class Movie {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "movie_id")
private long movieId;

@Column(name = "title")
private String title;

@ManyToMany
@JoinTable(
        name = "movie_actor",
        joinColumns = @JoinColumn(name = "movie_id"),
        inverseJoinColumns = {@JoinColumn(name = "actor_id")}
)
@JsonManagedReference
private List<Actor> actors = new ArrayList<>();

@ManyToOne
@JoinColumn(name = "CATEGORY_ID")
@JsonManagedReference
private Category category;
}

Answer 1

因此您必须在 API 中使其可访问。一种选择是将交集 table movie_actor 映射到实体 MovieActor 并将 Actor 和 Movie 之间的 ManyToMany 关系拆分为 OneToMany 与 MovieActor 的关系，如：

@Entity
@Data
@Table(name = "movie_actor")
@AllArgsConstructor
@NoArgsConstructor
public class MovieActor {
    @EmbeddedId
    private MovieActorId productOrderId = new MovieActorId();

    @ManyToOne(cascade = CascadeType.ALL, optional = false)
    @MapsId("movieId")
    @JoinColumn(name = "product_id", nullable = false)
    private Movie movie;

    @ManyToOne(cascade = CascadeType.ALL, optional = false)
    @MapsId("actorId")
    @JoinColumn(name = "order_id", nullable = false)
    private Actor actor;

    public void addMovieActor(Movie aMovie, Actor aActor) {
        movie = aMovie;
        actor = aActor;

        aMovie.getMovieActors().add(this);
        aActor.getMovieActors().add(this);
    }
}

@Embeddable
@Getter
@Setter
public class MovieActorId  implements Serializable {
    @Column(name = "movie_id")
    private Long movieId;

    @Column(name = "actor_id")
    private Long actorId;
}

@Entity
@Data
@Table(name = "actor")
@AllArgsConstructor
@NoArgsConstructor
public class Actor {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "actor_id")
    private long actorId;

    @OneToMany(mappedBy = "actor")
    private List<MovieActor> movieActors = new ArrayList<>();
}

@Entity
@Data
@Table(name = "movie")
@AllArgsConstructor
@NoArgsConstructor
public class Movie {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "movie_id")
    private long movieId;

    @OneToMany(mappedBy = "movie")
    private List<MovieActor> movieActors = new ArrayList<>();
}

现在您可以在查询中访问交集 table MovieActor。如果需要，您甚至可以向此 table 添加更多列。

在 Spring Boot JPA 中以多对多关系访问@JoinTable

Accessing @JoinTable in many-to-many relationship in Springboot JPA

java

jpa

h2

spring-data-jpa

spring-boot