How to reference a data already existing in the table with Hibernate

Question

I’m creating an api using Java with Springboot, and Ibernate. The idea is to save guests in the database, and these guests have a group, I don’t really understand the notes, but Mapeei with @Manytoone

@Entity
@Table(name = "con_convidado")
public class Convidado {

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

    @Length(max = 20)
    private String nome;


    @Enumerated(EnumType.STRING)
    private Gender genero;

    @ManyToOne(cascade = CascadeType.ALL)
    private Grupo grupo;


    @Enumerated(EnumType.STRING)
    private Age faixaEtaria;

    public Convidado() {

    }

Everything is working normally, but when I enter guests with the same group, in the database it creates a new line, and gets repeated information.

Group Class

@Entity
public class Grupo {

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

    private String nome;

How to reuse what is already on the table, or improve the relationship between them.

Answer 1

If your relationship is just one Convidado X in a Grupo Y and a Group can contain several different Guests, so their relationship is:

In his Entity Grupo is that it must contain:

@ManyToAOne(cascade = CascadeType.ALL)
    private Convidado convidados;