Persisting properties of parent class with annotation

bungrudi · **Joined:** Fri Jan 04, 2008 9:07 am **Posts:** 2

Hello,

I have a class Y, that extends class X. With hibernate annotations, how do I tell to persist some properties of the parent class?
Thanks before.

Rudi

carlolf · **Posted:** Mon Jun 30, 2008 2:18 am

That depends. If your superclass is used polymorphically, then you use

Code:

@Entity

.
If not, then you use

Code:

@MappedSuperClass

.

Either way, just annotate the properties of your superclass as usual.

Cameron McKenzie · **Posted:** Fri Jul 04, 2008 10:44 am

Of course, if the properties of the parent are passed down to the child class, they should be automatically be persisted if the inheritance mapping is done correctly.

Here's a little tutorial on how to map inherited classes using Hibernate and JPA annotations. It should clear up any doubt:

http://jpa.ezhibernate.com/Javacode/learn.jsp?tutorial=16mappinginheritancewithjpa

Regardless, the key is how the classes are mapped. Here's a simple inheritance mapping example:

Code:

package com.examscam.mappings; 
import javax.persistence.*;
@Entity
public class Ancestor {
  private Long id;
  private String nationality;
  @Id
  @GeneratedValue
  public Long getId() {return id;}
  public void setId(Long id) {this.id = id;}
  public String getNationality() {return nationality;}
  public void setNationality(String nationality) {
    this.nationality = nationality;
  }
}

Code:

package com.examscam.mappings;
import javax.persistence.*;
@Entity
public class  Parentextends Ancestor{
  private String lastName;
  public String getLastName() {return lastName;}
  public void setLastName(String lastName) {
        this.lastName = lastName;
  }
}

Code:

package com.examscam.mappings;
import javax.persistence.*;
@Entity
public class Child extends Parent {
  private String firstName;
  public String getFirstName() {return firstName;}
  public void setFirstName(String firstName) {
    this.firstName = firstName;
  }
}

When this code runs, you get all of the inherited properties persisted, as you can see from the database snapshot.

Code:

public static void main(String args[]) {
  Ancestor a = new Ancestor();
  a.setNationality("Korean");

  Parent p = new Parent();
  p.setNationality("Jewish");  p.setLastName("Steinberg");

  Child c = new Child();
  c.setNationality("Irish"); 
  c.setLastName("McKenzie");
  c.setFirstName("Cameron");

  Session session = HibernateUtil.beginTransaction();
  session.save(a); session.save(p); session.save(c);
  HibernateUtil.commitTransaction();
}

Code:

Hibernate:
insert into Ancestor (nationality, DTYPE) values (?, 'Ancestor')
Hibernate:
insert into Ancestor (nationality, lastName, DTYPE) values (?, ?, 'Parent')
Hibernate:
insert into Ancestor (nationality, lastName, firstName, DTYPE) values (?, ?, ?, 'Child')