spring-vaadin three tables joined

Hi,
 I have three tables, Groupauthorities,Roles and Groups.
Groupauthorities has three columns eg. id, role_id and group_id.
Roles also has two columns eg. id, rolename_x and groups also has two columns eg. id, groupname_x
Groupauthorities has many-to-one relationship with roles and groups. The groupauthorities must show in vaadin table as below
ID    Roles Name         Group Name
1      ROLE_ADMIN     Administrators
2      ROLE_USER      Administrators
3      ROLE_USER      Users

I googled for the solution how to use spring-data-jpa with many tables joined together and I found it as below
public interface MyRepository extends JpaRepository {
   String sql = "SELECT t1.id as id, t2.role_x as roleX, t3.groupname_x as groupnameX " +
                       "FROM group_authorities as t1, roles as t2, groups as t3 " +
                       "WHERE t2.id = t1.role_id " +
                       "AND t3.id = t1.group_id";
    @Query(name = sql, nativeQuery = true)
    List<Object[]> methodThatQueriesMultipleTables();
}
I use BeanItemContainer to load from the database to vaadin table. However, if I use this one as below, it would reject as it needs one class.
BeanItemContainer groupauthoritiesContainer = new BeanItemContainer<>(GroupAuthorities.class, Roles.class, Groups.class); 
The only one thing I can think of is using Vaadin SQLContainer addon. Remember I use Vaadin Spring addon. It will work with these two addons.

I am not happy with these addons together as I like to keep the codes clean and easy to look at.

What is the solution of using BeanItemContainer or others?

Looking foward to hearing from you.
 

I want to inform you that the problem is solved.

You just overwrite the toString() in the domain/model class.

For example,
@Entity
@Getter
@Setter
@Table(name = "groups")
public class Groups extends AbstractEntity {

    @Basic
    @Column(name = "groupname_x")
    private String groupnameX;

    @OneToMany(mappedBy = "groupsByGroupId")
    private Collection<GroupAuthorities> groupAuthoritiesById;

    @OneToMany(mappedBy = "groupsByGroupId")
    private Collection<GroupMembers> groupMembersesById;

    public Groups() {}

    public Groups(String groupnameX, Long userChanged) {
        this.groupnameX = groupnameX;
        this.userChanged = userChanged;
    }

    @Override    public String toString() {        return id + "," + groupnameX;    }}