Is my approach right while inserting a foreign key?

[chaitanya karthikk]

Hi all, I am new to hibernate and started practicing from yesterday. I tried with a simple insertion, selection code. Later thought to try a foreign key insertion. This is the code I used to insert records in 2 tables which has a foreign key.

Author.hbm.xml<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" > <hibernate-mapping> <class name="author.book.example.Author" table="author"> <id name="id" type="long" column="id"> <generator class="hilo" /> </id> <property name="name" type="string" column="name" length="100" /> </class> <class name="author.book.example.Book" table="books"> <id name="id" type="long" column="id"> <generator class="hilo" /> </id> <property name="name" type="string" column="name" length="100" /> <many-to-one name="author" class="author.book.example.Author" column="author" cascade="all" not-null="true" /> </class> </hibernate-mapping> Author.java

package author.book.example;

public class Author
{
	private String name;
	private long id;	
	public void setName(String name){
		this.name=name;
	}
	public String getName()	{
		return name;
	}
	public void setId(long id){
		this.id=id;
	}
	public long getId(){
		return id;
	}
}

Book.java

package author.book.example;


public class Book
{
	private long id;
	private String name;
	private Author author;
	public void setId(long id){
		this.id=id;
	}
	public long getId()	{
		return id;
	}
	public void setName(String name){
		this.name=name;
	}
	public String getName()	{
		return name;
	}
	public void setAuthor(Author author){
		this.author=author;
	}
	public Author getAuthor(){
		return author;
	}
}

Example.java

package author.book.example;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;

public class Example
{
	public static void main(String kk[])
	{
		Configuration cfg=new Configuration();
		cfg.configure();
		SessionFactory factory=cfg.buildSessionFactory();
		Session session=factory.openSession();
		Transaction tx=session.beginTransaction();
		Author author=new Author();
		author.setName("Herbert Schildt");
		Book book1=new Book();
		book1.setName("C Complete Refernce");
		book1.setAuthor(author);
		session.save(book1);
		Book book2=new Book();
		book2.setName("Java Complete Refernce");
		book2.setAuthor(author);
		session.save(book2);
		tx.commit();
		session.flush();
		session.close();
	}
}

The records are being successfully inserted.

My problem starts here. Suppose I want to insert another book for the same author. I am using the following approach.

package author.book.example;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;

public class Example
{
	public static void main(String kk[])
	{
		Configuration cfg=new Configuration();
		cfg.configure();
		SessionFactory factory=cfg.buildSessionFactory();
		Session session=factory.openSession();
		Transaction tx=session.beginTransaction();
		Author author=new Author();
		author.setId(720896);  //Author ID taken from database
		author.setName("Herbert Schildt");
		Book book1=new Book();
		book1.setName("Java Complete Refernce");
		book1.setAuthor(author);
		session.save(book1);
//		Book book2=new Book();
//		book2.setName("Java Complete Refernce");
//		book2.setAuthor(author);
//		session.save(book2);
		tx.commit();
		session.flush();
		session.close();
	}
}

I am taking the author's id and his name, then setting the Author.java POJO class and then setting name and author of the Book.java POJO class and then executing the program. The records are being successfully inserted. The problem is I have to set all details for Author.java POJO. If am not setting author.setName(String) a NULL is being inserted.

How to add a record in the child table without having to change the record in the parent table.

Hope you all understood my problem. Can anyone please shed some light on this issue. Thank you all in advance.

[chaitanya karthikk]

Is there anyone who can guide me?