Hibernate @ManyToMany 删除关系

问题描述

我有 2 个实体:User 和 UsersList.

I have 2 entities: User and UsersList.

@Entity
@Table(name = "USERS")
public class User {
    @Id
    @GeneratedValue
    @Column(name = "ID")
    private Long id;

    @ManyToMany(cascade = CascadeType.REMOVE, mappedBy = "users")
    private List<UsersList> usersLists = new ArrayList<UsersList>();

    public List<UsersList> getUsersLists() {
        return usersLists;
    }

    public void setUsersLists(List<UsersList> usersLists) {
        this.usersLists = usersLists;
    }
}

和

@Entity
@Table(name = "USERS_LIST")
public class UsersList {
    @Id
    @GeneratedValue
    @Column(name = "ID")
    private Long id;

    @ManyToMany
    private List<User> users = new ArrayList<User>();

 public List<User> getUsers() {
        return users;
    }

    public void setUsers(List<User> users) {
        this.users = users;
    }
}

和这样的代码:

// 1
List<User> dbUsers; // 3 the user instances are persisted in DB
UsersList usersList = new UsersList();
usersList.setUsers(dbUsers);

// 2 - now persist the usersList using hibernate...
saveWithHibernate(usersList);

//3 - delete using a persisted user
deleteWithHibernate(dbUsers.get(0).getId());

在哪里

deleteWithHibernate(Long id) {
        User usr = hibernateTemplate.get(User.class, id);
        hibernateTemplate.delete(usr);
}

在第 1 步中，我在 USERS (USER_ID) 表中有 3 行.

In step 1 I have 3 rows in the USERS (USER_ID) table.

在第 2 步(第二条评论)之后，我在 USERS_LIST (USERS_LIST_ID) 表中有 1 行，在连接表 USERS_LIST_USERS (USER_ID, USERS_LIST_ID) 中有 3 行.

After step 2 (second comment) I have 1 row in the USERS_LIST (USERS_LIST_ID) table and into the join table USERS_LIST_USERS (USER_ID, USERS_LIST_ID) 3 rows.

我想在第 3 步中实现以下目标:当我从表 USERS 中删除一个用户时 - 假设 USER_ID = 4 的用户，我只想从连接表中删除 USER_ID = 4 的行，和其他人留下来.

What I want to achieve in step 3 is the following: when I delete one user from the table USERS - let's say user with USER_ID = 4, I want just the row with USER_ID = 4 from the join table to be deleted, and the others to remain.

我的问题有注释解决方案吗?

Is there an annotation solution to my problem?

推荐答案

你需要的是@JoinTable 属性:

What you need is the @JoinTable attribute:

Hibernate 不知道多对多关系相互引用，并且可能会创建两个连接表.如果您在关系的两侧指定相同的@JoinTable，它将按预期工作.

Hibernate does not know that the many-to-many relations refer to each other and will probably create two join tables. If you specify the same @JoinTable on both sides of the relation it will work as expected.

确保 joinColumn 和 inverseJoinColumn 在对立面上是对立的关系的双方.

Make sure that the joinColumn and the inverseJoinColumn are opposites on the opposingsides of the relation.

• 一侧的joinColumn ==另一侧的inverseJoinColumn
• 一侧的inverseJoinColumn ==另一侧的joinColumn

我希望这会有所帮助.

@Entity
public class Role extends Identifiable {

    @ManyToMany(cascade ={CascadeType.MERGE, CascadeType.PERSIST, CascadeType.REFRESH})
    @JoinTable(name="Role_Permission",
            joinColumns=@JoinColumn(name="Role_id"),
            inverseJoinColumns=@JoinColumn(name="Permission_id")
        )
    public List<Permission> getPermissions() {
        return permissions;
    }

    public void setPermissions(List<Permission> permissions) {
        this.permissions = permissions;
    }
}

@Entity
public class Permission extends Identifiable {

    @ManyToMany(cascade = {CascadeType.MERGE, CascadeType.PERSIST, CascadeType.REFRESH})
    @JoinTable(name="Role_Permission",
            joinColumns=@JoinColumn(name="Permission_id"),
            inverseJoinColumns=@JoinColumn(name="Role_id")
        )
    public List<Role> getRoles() {
        return roles;
    }

    public void setRoles(List<Role> roles) {
        this.roles = roles;
    }

}

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