Hibernate Joined subclasses annotation:
Each subclass can also be mapped to its own table. This is also called table-per-subclass mapping strategy. An inherited state is retrieved by joining with the table of the superclass.
A discriminator column is not required for this mapping strategy. Each subclass must, however, declare a table column holding the object identifier.
POJO
Book.java
package com.candidjava.hibernate;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;
import javax.persistence.Table;
@Entity
@Table(name = "booktype")
@Inheritance(strategy = InheritanceType.JOINED)
public class Book {
private int id;
private String title;
private String author;
private double cost;
public void setId(int id) {
this.id = id;
}
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column
public int getId() {
return id;
}
public void setTitle(String title) {
this.title = title;
}
@Column
public String getTitle() {
return title;
}
public void setAuthor(String author) {
this.author = author;
}
@Column
public String getAuthor() {
return author;
}
public void setCost(double cost) {
this.cost = cost;
}
@Column
public double getCost() {
return cost;
}
}
International Book
InternationalBook.java
package com.candidjava.hibernate;
import javax.persistence.Entity;
import javax.persistence.PrimaryKeyJoinColumn;
import javax.persistence.Table;
@Entity
@Table(name = "IntlBook")
@PrimaryKeyJoinColumn(name = "ID")
public class InternationalBook extends Book {
private String languages;
private int region;
public InternationalBook() {
}
public void setLanguages(String s) {
languages = s;
}
public String getLanguages() {
return languages;
}
public void setRegion(int i) {
region = i;
}
public int getRegion() {
return region;
}
}
Special Edition Book
SpecialEditionBook.java
package com.candidjava.hibernate;
import javax.persistence.Entity;
import javax.persistence.PrimaryKeyJoinColumn;
import javax.persistence.Table;
@Entity
@Table(name = "SplEdiBook")
@PrimaryKeyJoinColumn(name = "ID")
public class SpecialEditionBook extends Book {
private String newfeatures;
public SpecialEditionBook() {
}
public void setNewfeatures(String s) {
newfeatures = s;
}
public String getNewfeatures() {
return newfeatures;
}
}
Inserting record into Joined Sub Classes
public void insertBook(Book bk) {
try {
Session s = getSession();
Transaction transaction = s.beginTransaction();
s.save(bk);
transaction.commit();
} catch (HibernateException e) {
e.printStackTrace();
}
}Test Inserting record in Joined Sub Classes
package com.candidjava.hibernate;
public class TestInsertBook {
public static void main(String arg[]) {
try {
BookDao m = new BookDao();
Book bk = new Book();
bk.setAuthor("Surrendar");
bk.setCost(760);
bk.setTitle("oracle");
InternationalBook ib = new InternationalBook();
ib.setAuthor("sivaraman");
ib.setCost(960);
ib.setTitle("oracle");
ib.setLanguages("tamil");
ib.setRegion(12);
SpecialEditionBook sb = new SpecialEditionBook();
sb.setAuthor("surrendar");
sb.setCost(550);
sb.setTitle("j2ee");
sb.setNewfeatures("Jquery");
m.insertBook(bk);
m.insertBook(ib);
m.insertBook(sb);
} catch (Exception e) {
System.out.println(e);
}
}
}
Retrieving or getting record from Joined Sub Classes
public Book getBook(int id) {
Book sd = null;
try {
Session s = getSession();
sd = (Book) s.get(Book.class, id);
} catch (HibernateException e)
{
System.out.println(e.getMessage());
}
return sd;
}Test to Retrieve or get record from Joined Sub Classes
package com.candidjava.hibernate;
public class TestGetBook {
public static void main(String arg[]) {
BookDao ms = new BookDao();
Book b = ms.getBook(14);
System.out.println(b.getAuthor());
System.out.println(b.getTitle());
System.out.println(b.getCost());
if (b instanceof InternationalBook) {
InternationalBook ib = (InternationalBook) b;
System.out.println(ib.getLanguages());
System.out.println(ib.getRegion());
}
if (b instanceof SpecialEditionBook) {
SpecialEditionBook sb = (SpecialEditionBook) b;
System.out.println(sb.getNewfeatures());
}
}
}Download
