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Example of @Generated in Hibernate

By Arvind Rai, May 28, 2013
Hibernate provides the facility to update the entity for those database values which are generated at insert or row update time. @Generated belongs to org.hibernate.annotations. @Generated is used at property level. There are different GenerationTime.

GenerationTime.INSERT

GenerationTime.INSERT updates the entity at insert time. For GenerationTime.INSERT, the property should not be insetable.
 @Generated(GenerationTime.INSERT) 
 @Column(name="create_date", insertable=false)
 

GenerationTime.ALWAYS

GenerationTime.ALWAYS updates the entity at both time insert and update. In the case of GenerationTime.ALWAYS, the property should not be insertable and updatable.
@Generated(GenerationTime.ALWAYS) 
@Column(name="create_date", insertable=false,updatable=false)
 
Find the complete example.

State.java
package com.concretepage.persistence;
import java.io.Serializable;
import java.util.Calendar;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
import org.hibernate.annotations.Generated;
import org.hibernate.annotations.GenerationTime;
import org.hibernate.annotations.Index;
@Entity
@Table(name = "state")
public class State  implements Serializable{
	private static final long serialVersionUID = 1L;
	@Id
	@GeneratedValue
	@Column(name = "id")
    private int id;
			
	@Temporal(TemporalType.TIMESTAMP)
	@Generated(GenerationTime.ALWAYS) 
	@Column(name="create_date", insertable=false,updatable=false)
	private Calendar createDate;
	
	@Column(name="name")
	@Index(name="nameIndex")
	private String name;
	public Calendar getCreateDate() {
		return createDate;
	}
	public void setCreateDate(Calendar createDate) {
		this.createDate = createDate;
	}
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}	
 }
 


HibernateUtil.java
package com.concretepage.util;
import java.util.Properties;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.AnnotationConfiguration;
import com.concretepage.persistence.State;
public class HibernateUtil {
	private static final SessionFactory concreteSessionFactory;
		static {
		 try {
				Properties prop= new Properties();
				prop.setProperty("hibernate.connection.url", "jdbc:mysql://localhost:3306/hibernate");
				prop.setProperty("hibernate.connection.username", "root");
				prop.setProperty("hibernate.connection.password", "");
				prop.setProperty("hibernate.hbm2ddl.auto", "update");
				prop.setProperty("dialect", "org.hibernate.dialect.MySQLDialect");
				
				concreteSessionFactory = new AnnotationConfiguration()
			   .addPackage("com.concretepage.persistence")
					   .addProperties(prop)
					   .addAnnotatedClass(State.class)
					   .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();
	         State s= new State();
	         s.setName("Delhi");
	         session.save(s);
	         session.getTransaction().commit();
	         System.out.println("Create Date:"+s.getCreateDate().getTime());
             session.close();
	   }
	}
 
Database should be created as below to run the example.
CREATE TABLE `state` (
	`id` INT(11) NOT NULL AUTO_INCREMENT,
	`create_date` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
	`name` VARCHAR(255) NOT NULL,
	PRIMARY KEY (`id`),
	INDEX `nameIndex` (`name`)
)
COLLATE='latin1_swedish_ci'
ENGINE=InnoDB
AUTO_INCREMENT=2;
 
POSTED BY
ARVIND RAI
ARVIND RAI
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