Spring 数据 JPA | 从 @ManyToMany 关系中的 @JoinTable 中删除 MyGroup 时仅删除条目

Question

I am using spring Boot 2.0 and spring data jpa with hibernate. I am creating a web application where a user can make group, and other user can join this group. For this, i created two Entity named User and MyGroup as below.

@MappedSuperclass
public class BaseEntity {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

}



@Entity
public class User extends BaseEntity {

    String name;

    @ManyToMany(fetch = FetchType.LAZY, mappedBy = "members")
    Set<MyGroup> joinedGroup= new HashSet<MyGroup>();

}

@Entity
public class MyGroup extends BaseEntity {

    String name;

    @ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    Set<User> members = new HashSet<User>();

}

Here, I want that, If a group is removed, then it's relationship entry from joined table is also removed but user should not be removed. This code is removing even users also. plz suggest how may i delete group and relationship entry only.

Answer 1

CascadeType.ALL at MyGroup.java removes all the associated users upon deleting a group. So, replace the cascade CascadeType.ALL with CascadeType.MERGE