java - JPA 中的多对多映射

Question

我在表 Users 和 Groups 之间有一个 M:N 关系。现在我正在尝试使用 JPA 连接这两个表，但我总是遇到此异常:

Multiple writable mappings exist for the field [GROUPS.name]. Only one may be defined as writable, all others must be specified read-only.

这是我的 Users 类(为简洁起见，我没有附上 getter 和 setter)，它由 Admin 类和 SignedUser 类实现具有一些额外的属性。

@Entity
@Inheritance(strategy = InheritanceType.JOINED)
public class Users implements Serializable {

    @Id
    @Column(name = "login", nullable = false, length = 10)
    private String login;

    @Column(name = "name", nullable = false, length = 30)
    private String name;

    @Column(name = "surname", nullable = false, length = 50)
    private String surname;

    @Column(name = "email", nullable = false, length = 100)
    private String email;

    @Column(name = "password", nullable = false, length = 20)
    private String password;

    @ManyToMany(mappedBy="users")
    private List<Groups> groups;

这是 Group 类:

@Entity
public class Groups implements Serializable {

    @Id
    @Column(name = "name", nullable = false, length = 20)
    private String groupName;

    @Column(name = "name", nullable = false, length = 50)
    private String descr;

    @ManyToMany
    @JoinTable(name = "user_group",
               joinColumns = {@JoinColumn(name = "groupName")},
               inverseJoinColumns = {@JoinColumn(name = "login")})
    private List<Users> users;

我还尝试将 JoinTable 注释放入 Users 类中，但结果相同。在此先感谢您的任何建议。

Answer 1

在 Group 类中，您有两个映射列 name 作为属性 groupName 和 descr。

该错误与 ManyToMany 无关。