Hibernate的@ManyToMany删除关系 [英] Hibernate @ManyToMany delete relation

问题描述

我有2个实体：用户和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code像这样的：

// 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());

其中，

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

在步骤1中我有3行中的用户（USER_ID）表。

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

在步骤2中（第二个评论）我在USERS_LIST（USERS_LIST_ID）表和插入连接表USERS_LIST_USERS（USER_ID，USERS_LIST_ID）3行1列。

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步实现如下：当我从USERS表中删除一个用户 - 让我们说有USER_ID = 4的用户，我想只是一行USER_ID = 4从连接表被删除，和其他人保持

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.

是否有标注解决我的问题？

Is there an annotation solution to my problem?

推荐答案

您需要的是@JoinTable属性：

What you need is the @JoinTable attribute:

Hibernate不知道，很多一对多的关系互相引用，并可能会创建两个连接表。如果指定的关系，双方在同一@JoinTable它会正常工作。

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.

请确保joinColumn和inverseJoinColumn是对立的对立
关系的两侧。

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

• 在一边joinColumn ==在另一边inverseJoinColumn


• 在一边inverseJoinColumn == joinColumn在另一边

我希望这有助于。

@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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