Question

@Embeddable
@MappedSuperclass
public class Address {
  private String street;
  private String city;

public String getStreet(){ return street;}
public String getCity(){ return city;}
public String setStreet(Sting street){ this.street= street;}
public String setCity(String city){ this.city=city;}

}

import org.hibernate.annotations.Entity;
@Entity
public class AddressHistory extends Address {
 Long id;
 @Id @XmlTransient
 @GeneratedValue(strategy = GenerationType.AUTO)
  public Long getId() {
    return m_id;
  }

 public void setId(Long m_id) {
    this.m_id = m_id;
 }
}

Here is my scenario, I want to store address of a person. And I also have to store all the address that a person has live before. So what I am doing is I am embedding current address in person table and would like to store all his/her pervious address in history table. To achieve this. I made Address class embeddable and embedded it into person table and HistoryAddress table. But as of OOPS concept. HistoryAddress is a Address, so it is not good to do composition of Address class into AddressHistory. Then I decided to extends AddressHistory from Address class. BUt when I do this hibernate gives me this error

Use of @OneToMany or @ManyToMany targeting an unmapped class AddressHistory.

But clearly I have mapped AddressHistory
Can we do this ? Can we extend Entity from Embedded class ?

Answer 1

No, entity cannot extend embeddable. In JPA 2.0 specification this is told as follows:

An entity can have a non-entity superclass, which may be either a
concrete or abstract class.[22]
…
[22] The superclass must not be an
embeddable class or id class.

Also target of relationship must be Entity. Embeddable is not entity, it does not have identity of its own. If you want collection of embeddables, use @ElementCollection.