Spring 引导数据 JPA 查询具有 @ManyToMany 集合的实体

Question

我有一个名为 Club 的实体，它与一个名为 Type 的实体具有 @ManytoMany 关系。这种类型有各种俱乐部标签，例如它是足球俱乐部还是游泳俱乐部。所以一个俱乐部可以有多种类型，也可以在俱乐部之间共享某种类型。当我想 select 一个俱乐部时，我还想显示与访问类型集合的俱乐部相关联的标签。我应该如何实现这一目标？

@Data
@Entity
@EntityListeners(AuditingEntityListener.class)
public class Club {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;

    @Column(length = 20)
    private String name;

    @Column(length = 20)
    private String shortName;

    @Column(length = 80)
    private String description;

    @Column(length = 50)
    private String email;

    private boolean status;

    @Lob
    private Blob logo;

    @Lob
    private Blob cover;

    @Column(length = 50)
    private String website;

    private double longitude;

    private double latitude;

    @Column(length = 20)
    private String registrationId;

    @CreatedDate
    @Temporal(TemporalType.DATE)
    @Column(nullable = false, updatable = false)
    private Date registrationDate;

    @Temporal(TemporalType.DATE)
    private Date lastActiveDate;

    @OneToMany(mappedBy = "club")
    private List<Favourite> favourites;

    @ManyToMany
    private List<Type> type;

    @OneToOne(fetch = FetchType.LAZY)
    private Address address;

}
@Entity
@Data
@EntityListeners(AuditingEntityListener.class)
public class Type {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;

    @Column(length = 10)
    private String tag;

    @ManyToMany(mappedBy = "type")
    private List<User> user;

    @ManyToMany(mappedBy = "type")
    private List<Club> club;

    @CreatedDate
    @Temporal(TemporalType.DATE)
    @Column(nullable = false, updatable = false)
    private Date createdDate;

}

在 ClubRespository.java 中，我正在尝试像这样访问类型集合的标记变量。

@Repository
public interface ClubRepository extends JpaRepository<Club, Integer> {

    @Query("SELECT new com.service.payload.response.ClubSend(c.id, c.name, c.type.tag, c.shorName, c.description, c.email, c.logo, c.cover, c.longitude, c.latitude, c.address) FROM Club c JOIN c.type WHERE c.id=c.type.club.id")
    List<Club> findAllClubs();

}

ClubSend 是一个 DTO class 我创建它是为了映射我想要显示的字段，但是当我这样做时，我收到了这个错误。

Caused by: java.lang.IllegalArgumentException: org.hibernate.QueryException: illegal attempt to dereference collection [club0_.id.type] with element property reference [tag] [SELECT new com.vayemo.mysponsor.service.payload.response.ClubSend(c.id, c.name, c.type.tag, c.shorName, c.description, c.email, c.logo, c.cover, c.longitude, c.latitude, c.address) FROM com.vayemo.mysponsor.service.model.Club c JOIN c.type WHERE c.id=c.type.club.id]

Caused by: org.hibernate.QueryException: illegal attempt to dereference collection [club0_.id.type] with element property reference [tag] [SELECT new com.vayemo.mysponsor.service.payload.response.ClubSend(c.id, c.name, c.type.tag, c.shorName, c.description, c.email, c.logo, c.cover, c.longitude, c.latitude, c.address) FROM com.vayemo.mysponsor.service.model.Club c JOIN c.type WHERE c.id=c.type.club.id]

Caused by: org.hibernate.QueryException: illegal attempt to dereference collection [club0_.id.type] with element property reference [tag]

Answer 1

您的问题是查询中的 c.type 是一个列表，因此无法取消引用 c.type.club。如果要访问类型对象，则需要在连接期间为其提供别名（如 ... FROM Club c JOIN c.type t ...），但据我所知，您的 where 子句隐含在 [=13 的声明中=]关系。如果您想了解更多详情，请查看 this Whosebug answer.

Spring 引导数据 JPA 查询具有 @ManyToMany 集合的实体

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