Hibernate Inheriatance mapping Table per class example annotation based


A third option is to map only the concrete classes of an inheritance hierarchy to tables. This is called the table-per-concrete-class strategy. Each table defines all persistent states of the class, including the inherited state.

In Hibernate, it is not necessary to explicitly map such inheritance hierarchies. You can map each class as a separate entity root. However, if you wish use polymorphic associations (e.g. an association to the superclass of your hierarchy), you need to use the union subclass mapping.

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 = "book1")
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public class Book {
	@Id
	@GeneratedValue(strategy = GenerationType.TABLE)
	int id;
	@Column(name = "title")
	String title;
	@Column(name = "author")
	String author;
	@Column(name = "cost")
	double cost;

	public Book() {
	}
	public Book(String title, String author, double cost) {
		this.title = title;
		this.author = author;

		this.cost = cost;
	}
	public void setId(int id) {
		this.id = id;
	}
	public int getId() {
		return id;
	}
	public void setTitle(String title) {
		this.title = title;
	}
	public String getTitle() {
		return title;
	}
	public void setAuthor(String author) {
		this.author = author;
	}
	public String getAuthor() {
		return author;
	}
	public void setCost(double cost) {
		this.cost = cost;
	}
	public double getCost() {
		return cost;
	}
}

 International Book

InternationalBook.java

package com.candidjava.hibernate;

import javax.persistence.AttributeOverride;
import javax.persistence.AttributeOverrides;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Table;

@Entity
@Table(name = "InternationalBook")
@AttributeOverrides({
		@AttributeOverride(name = "id", column = @Column(name = "id")),
		@AttributeOverride(name = "title", column = @Column(name = "title")),
		@AttributeOverride(name = "author", column = @Column(name = "author")),
		@AttributeOverride(name = "cost", column = @Column(name = "cost"))

})
public class InternationalBook extends Book {
	@Column(name = "language")
	private String languages;
	@Column(name = "region")
	private int region;

	public InternationalBook() {
	}
	public InternationalBook(String title, String author, double cost,
			String language, int region) {
		super(title, author, cost);

		languages = language;
		this.region = region;
	}
	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.AttributeOverride;
import javax.persistence.AttributeOverrides;
import javax.persistence.Column;
import javax.persistence.Entity;

@Entity
@AttributeOverrides({
		@AttributeOverride(name = "id", column = @Column(name = "id")),
		@AttributeOverride(name = "title", column = @Column(name = "title")),
		@AttributeOverride(name = "author", column = @Column(name = "author")),
		@AttributeOverride(name = "cost", column = @Column(name = "cost"))
})
public class SpecialEditionBook extends Book {
	@Column(name = "newfeatures")
	private String newfeatures;
	public SpecialEditionBook() {
	}
	public SpecialEditionBook(String title, String author, double cost,
			String features) {
		super(title, author, cost);
		newfeatures = features;
	}
	public void setNewfeatures(String s) {
		newfeatures = s;
	}
	public String getNewfeatures() {
		return newfeatures;
	}
}
Inserting record into Table per class annotation
public void insertBook(Book bk) {
		try {
			Session s = getSession();
			Transaction transaction = s.beginTransaction();
			s.save(bk);
			transaction.commit();
		} catch (HibernateException e) {
			e.printStackTrace();
		}
	}

Test to Insert record into Table per class annotation
package com.candidjava.hibernate;

public class TestInsertBook {
	public static void main(String arg[]) {
		try {
			BookDao m = new BookDao();
			Book bk = new Book();
			bk.setAuthor("sivaraman");
			bk.setCost(760);
			bk.setTitle("oracle");

			InternationalBook ib = new InternationalBook();
			ib.setAuthor("siva");
			ib.setCost(1000);
			ib.setTitle("Spring");
			ib.setLanguages("english");
			ib.setRegion(12);

			SpecialEditionBook sb = new SpecialEditionBook();
			sb.setAuthor("sivasamy");
			sb.setTitle("j2ee");
			sb.setNewfeatures("webservices");
			sb.setCost(1000);
			m.insertBook(bk);
			m.insertBook(ib);
			m.insertBook(sb);
		} catch (Exception e) {
			System.out.println(e);
		}
	}

}

Retrieving or getting record from Table per class
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 Table per class
package com.candidjava.hibernate;

public class TestGetBook {
	public static void main(String arg[]) {
		BookDao ms = new BookDao();

		Book b = ms.getBook(1);

		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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