如何解决将非集合映射为@OneTomany、@ManyTomany或@CollectionOfElements的非法尝试

Question

@Entity
@Table(name = "user_roles_activity")
public class UserRolesActivity {

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

    @Column(name = "user_id")
    private Long userId;

    @Column(name = "role_id")
    private Long roleId;

    @OneToMany
    @JoinTable(name = "user_role_activities_mapping", joinColumns = @JoinColumn(name = "user_roles_id"), inverseJoinColumns = @JoinColumn(name = "activity_id"))
    private Activity activity;

}

@Entity
@Table(name = "activities")
public class Activity {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

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

}

Answer 1

从错误：

非法尝试将非集合映射为@onetomany、@manytomany或@collectionofelements

您试图在不是集合的东西上建立OneToMany关系。因此，如果根据您的需求，每个UserRolesActivity映射到许多活动是有意义的，那么您可以使用如下内容：

@Entity
@Table(name = "user_roles_activity")
public class UserRolesActivity {

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

@Column(name = "user_id")
private Long userId;

@Column(name = "role_id")
private Long roleId;

@OneToMany
@JoinTable(name = "user_role_activities_mapping", joinColumns = @JoinColumn(name = "user_roles_id"), inverseJoinColumns = @JoinColumn(name = "activity_id"))
private List<Activity> activities;

}