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@GeneratedValue with strategy=GenerationType.IDENTITY in Hibernate

By Arvind Rai, May 16, 2013
@GeneratedValue generates the value for the column of database table. In case of GenerationType. IDENTITY , value is set by table itself that should be unique. It is used as
 @GeneratedValue(strategy=GenerationType.IDENTITY)
 
Find the example below.

EduCourse.java
package com.concretepage.persistence;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name = "edu_course")
public class EduCourse {
	@Id
	@GeneratedValue(strategy=GenerationType.IDENTITY)
	private int id;
	
	@Column(name = "course_name")
	private String courseName;
	
	@Column(name = "duration")
	private int duration;

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getCourseName() {
		return courseName;
	}

	public void setCourseName(String courseName) {
		this.courseName = courseName;
	}

	public int getDuration() {
		return duration;
	}

	public void setDuration(int duration) {
		this.duration = duration;
	}
}
 





HibernateUtil.java
package com.concretepage.util;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.AnnotationConfiguration;

import com.concretepage.persistence.EduCourse;

public class HibernateUtil {
	private static final SessionFactory concreteSessionFactory;
	static {
		try {

			concreteSessionFactory = new AnnotationConfiguration().configure()
					.buildSessionFactory();
		} catch (Throwable ex) {
			throw new ExceptionInInitializerError(ex);
		}
	}

	public static Session getSession() throws HibernateException {
		return concreteSessionFactory.openSession();
	}

	public static void main(String... args) {
		Session session = getSession();
		session.beginTransaction();

		EduCourse course = new EduCourse();
		course.setCourseName("B.Sc");
		course.setDuration(3);
		session.save(course);
		
		session.getTransaction().commit();
		session.close();
	}
}
 


hibernate.cfg.xml
 <!DOCTYPE hibernate-configuration PUBLIC
    "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
    "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
  <session-factory>
    <property name="hibernate.connection.url">
    jdbc:mysql://localhost:3306/hibernate</property>
    <property name="hibernate.connection.username">root</property>
    <property name="hibernate.connection.password"></property>
    <property name="hibernate.connection.pool_size">10</property>
    <property name="show_sql">true</property>
    <property name="dialect">org.hibernate.dialect.MySQLDialect</property>
    <property name="hibernate.hbm2ddl.auto">update</property>
    <mapping class="com.concretepage.persistence.EduCourse"/>
                
   </session-factory>
</hibernate-configuration>
 


edu_course Table
 CREATE TABLE `edu_course` (
	`id` INT(11) NOT NULL AUTO_INCREMENT,
	`course_name` VARCHAR(255) NULL DEFAULT NULL,
	`duration` INT(11) NULL DEFAULT NULL,
	PRIMARY KEY (`id`)
)
COLLATE='latin1_swedish_ci'
ENGINE=InnoDB;

 
POSTED BY
ARVIND RAI
ARVIND RAI
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