@javax.persistence.Entity
@Table(name="Parent")
@Access(AccessType.FIELD)
public class Parent implements Entity<Long>{
   
    @Id
    @Column(name="ID", unique = true, nullable = false)
    @GeneratedValue(generator = "DEFAULT_SEQ")
    @SequenceGenerator(name = "DEFAULT_SEQ", sequenceName = "DEFAULT_SEQ", allocationSize = 1)
    public Long id;

    //Get and Set metods 
}

@javax.persistence.Entity
@Table(name="Children")
@Access(AccessType.FIELD)
public class Children implements Entity<Long>{
   
    @Id
    @Column(name="ID", unique = true, nullable = false)
    @GeneratedValue(generator = "DEFAULT_SEQ")
    @SequenceGenerator(name = "DEFAULT_SEQ", sequenceName = "DEFAULT_SEQ", allocationSize = 1)
    public Long id;

    @ManyToOne
    @JoinColumn(name = "PARENT_ID")
    public Parent parent;

    //Get and Set metods 
}

@OneToMany(fetch=FetchType.EAGER, mappedBy = "parent")
public List<Children> childrens;

@OneToMany(fetch=FetchType.LAZY, mappedBy = "parent")
public List<Children> childrens;