Hibernate的@ManyToMany删除关系

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 opposingsides 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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