@Entity
@Table(name = "APP_USER", indexes = { @Index(name = "USER_ORG_GROUP_INDX", columnList = "GROUP_ID") })
public class User 


    @ManyToMany
    @JoinTable(
            name = "APP_USER_ROLE",
            joinColumns = @JoinColumn(name = "USER_ID", referencedColumnName="ID"),
            inverseJoinColumns = @JoinColumn(name="ROLE_ID", referencedColumnName="ID")
    )
    List<Role> roles;

User savedUser = userRepository.save(user);

Hibernate: 
    update
        app_role 
    set
        code=?,
        name=?,
        system=? 
    where
        id=?
Hibernate: 
    insert 
    into
        app_user_role
        (user_id, role_id) 
    values
        (?, ?)