java - 使用 hibernate 管理多对多关系

Question

我正在制作简单的 spring mvc web 应用程序，并且我正在将 hibernate 与 oracle 结合使用。我有两个模型 - 用户和角色，我想定义它们之间的多对多关系。我看过几个教程并定义了我的模型，如下所示:

这是User类:

@Entity
@Table(name = "AppUser")
public class User {

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "id_sequence")
    @SequenceGenerator(name = "id_sequence", sequenceName = "ID_SEQ")
    @Column(name = "Id")
    private int id;

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

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


    @ManyToMany
    (
        fetch = FetchType.LAZY,
        cascade = {
                      CascadeType.PERSIST,
                      CascadeType.MERGE
                  }
    )
    @JoinTable
    (
        name = "user_roles", 
        joinColumns = { @JoinColumn(name = "user_id", referencedColumnName = "id") }, 
        inverseJoinColumns = { @JoinColumn(name = "role_id", referencedColumnName = "id") }
    )
    private Set<Role> roles = new HashSet<Role>(0);

    //getters and setters....
} 

这是角色类:

@Entity
@Table(name = "role")
public class Role {

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "id_sequence")
    @SequenceGenerator(name = "id_sequence", sequenceName = "ID_SEQ")
    private int id;

    private String role;

    @ManyToMany
    (
        fetch = FetchType.LAZY, 
        cascade = {
                      CascadeType.PERSIST,
                      CascadeType.MERGE
                  },
        mappedBy = "roles"
    )
    private Set<User> users;

    //getters and setters....
}

当我在服务器上运行此应用程序时，出现以下错误:

此错误表明该表不存在，所以我感兴趣的是我应该手动创建它(我不这么认为)还是我在这里遗漏了任何内容？

Answer 1

只需将@ManyToMany 放在一个地方即可。

请删除角色实体中的@ManyToMany。 您可以检查下面的链接以使用 oracle 数据库处理@ManyToMany。 我希望这对您有所帮助:

https://gerardnico.com/jpa/many-to-many#oracle_database