I have 2 tables email_address and group_email

email_address
id
name
email
is_group

group_email
id
group_id (one to many relationship with id filed email_address table)
email_addr_id (one to many relationship with id filed of email_address table )

I want to get list of email_addresses and if it is group then also list of group email addresses. How should I configure entity?

@Entity
@Table(name = "email_address")
public class EmailAddressDom {

@Id
@Column(name = "id")
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "email_address_id_seq")
@SequenceGenerator(name = "email_address_id_seq", sequenceName = "email_address_id_seq")
private int id;

@Column(name = "name")
private String name;

@Column(name = "email")
private String email;

@Column(name = "is_group")
private boolean isGroup;

// which annotation should be there
private List<EmailAddressDom> groupEmails;

Could you describe the design goal? It seems very strange to have a is_group column on your email_address table since it seems to represent an email address for a person. The group_email table is where you seem to want to define your groups? The typical design for such a thing, from a purely relational perspective, would be that the group_email would be many:many with email_address - one email could belong to multiple groups and one group can contain many emails. These would probably be best modeled as Entities and would use a bi-directional association.

I would recommend you think about the design a bit more and then grab one of the many good books on JPA/Hibernate and read about some of these basic associations.