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LockOptions, Session.buildLockRequest() and LockRequest in Hibernate

By Arvind Rai, February 15, 2015
In this page we will learn LockOptions, Session.buildLockRequest() and LockRequest in hibernate. LockOptions represents different lock mode to lock entity object using Session.buildLockRequest(). This method returns LockRequest and using its method lock() we can lock the entity instance. Find the code snippet.
Student s = new Student(3, 22,"Ram");
LockRequest lockRequest = session.buildLockRequest(LockOptions.READ);
lockRequest.lock(s); 
LockOptions : org.hibernate.LockOptions has different lock mode like READ, UPGRADE and NONE etc.
Session.buildLockRequest() A session method that builds Lock Request. This method accepts lock mode to build lock request.
LockRequest : This is the inner class of Session. Using lock() method we lock the entity object.

Lock Object in READ Mode Demo

In this example, we will lock an entity in READ mode. Try to read data for the entity and we will be able to read. Use Session.refresh() to re-read the data.
ReadData.java
package com.concretepage;
import org.hibernate.LockOptions;
import org.hibernate.Session;
import org.hibernate.Session.LockRequest;
public class ReadData {
	public static void main(String[] args) {
		Session session = HibernateUtil.getSessionFactory().openSession();
		session.beginTransaction();
		LockRequest lockRequest = session.buildLockRequest(LockOptions.READ);
		Student s = (Student) session.load(Student.class, new Integer(1));
		lockRequest.lock(s);
		//re-read the object
		session.refresh(s);
		session.getTransaction().commit();
		session.close();
	}
} 
Find the output.
Hibernate: select student0_.id as id1_0_0_, student0_.age as age2_0_0_, student0_.name as name3_0_0_ from student student0_ where student0_.id=?
Hibernate: select student0_.id as id1_0_0_, student0_.age as age2_0_0_, student0_.name as name3_0_0_ from student student0_ where student0_.id=? 
We can see select query, it means we are able to read data from database. But if we try to save data for this entity, we will get exception. Find the code to test it.
SaveData.java
package com.concretepage;
import org.hibernate.LockOptions;
import org.hibernate.Session;
import org.hibernate.Session.LockRequest;
public class SaveData {
	public static void main(String[] args) {
		Session session = HibernateUtil.getSessionFactory().openSession();
		Student s = new Student(3, 22,"Ram");
		session.beginTransaction();
		LockRequest lockRequest = session.buildLockRequest(LockOptions.READ);
		lockRequest.lock(s);
		//Unable to save as object is locked in read mode.
		session.save(s);
		session.getTransaction().commit();
		session.close();
	}
} 
Now we will get exception as below because object is locked in READ mode.
Hibernate: select id from student where id =?
Exception in thread "main" org.hibernate.StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect) : [com.concretepage.Student#3]
	at org.hibernate.dialect.lock.SelectLockingStrategy.lock(SelectLockingStrategy.java:93) 

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POSTED BY
ARVIND RAI
ARVIND RAI
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