Hibernate Joined subclasses example annotation

By candid | Posted : Sep 5, 2015 | Updated : Dec 2, 2016

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());

		}

	}

}

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Hibernate Joined subclasses example annotation

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