@Entity
@Table(name = "REF")
public class Ref {
	// Some fields...
}

@Entity
@Table(name = "ABSTRACT_OBJECT")
@Inheritance(strategy = InheritanceType.JOINED)
@DiscriminatorColumn(name = "TYPE_OBJECT")
public abstract class AbstractObject {
	@Id
	private Long id;

	@ManyToOne(fetch = FetchType.EAGER)
	@JoinColumn(name = "FK_REF")
	private Ref ref;

	@Column(name = "TYPE_OBJECT")
	private String typeObject
}

@Entity
@Table(name = "OBJECT_ONE")
@DiscriminatorValue("ONE")
public class ObjectOne extends AbstractObject {
	// Some fields...
}

@Entity
@Table(name = "CHILED")
public class Child {
	@Id
	private Long id;

	@ManyToOne(fetch = FetchType.EAGER)
	@JoinColumn("FK_OBJECT_ONE")
	private ObjectOne objectOne;

	// Some fields...
}