Insert into one table of ManytoMany and joining table hibernate-CodePudding

Hi I am new to Hibernate and trying to build a Rest APP.

I have 3 tables in the database as shown in the above image.

USERS table has ManyToMany relation with GROUPS table and USER_GROUP is an association table.

I am using ORM, Hibernate and CurdRepository.

I am able to insert into users table and group table with save() method of CurdRepository.

Now I am trying to add a row in GROUPS table and USER_GROUP table only. Can anyone lead me to the right direction?

For example:

I want to add an groupid to GROUPS table and then associate it with an user id

Let's say I want to insert (10) groupid in GROUPS and (14,10) in USER_GROUP table.

Is it doable with ORM, if yes how?

Thanks in advance

CodePudding user response：

There are many articles online about exactly this model to showcase how to use Hibernate. Here is one article I quickly found by googling for "hibernate user group example": https://www.codejava.net/frameworks/hibernate/hibernate-many-to-many-association-annotations-example

CodePudding user response：

To use existing connecting table, USE_GROUP, User entity will be like following .

@Entity
public class Users {
    @Id
    private Integer userid;

    private String password;

    @ManyToMany(cascade = { CascadeType.MERGE, CascadeType.PERSIST })
    @JoinTable(name = "USER_GROUP", joinColumns = { @JoinColumn(name = "USERID") }, 
        inverseJoinColumns = { @JoinColumn(name = "GROUPID") })
    private Set<Groups> groups;

    // Getter, Setter
}

And then client code, add new User and Group, will be something like below.

User user = new User()
// set password , etc
Set<Groups> groups = new HashSet<>();
Group group = new Group();
// set 
groups.add(group);

user.setGroups(groups);

userRepository.save(user);