Hibernate : Session Lock
This tutorial contains how Session.lock() method works in Hibernate.
Hibernate : Session Lock :-
The lock() method obtains the specified lock level upon the given object. It
allows your application
to reattach the object to the session. It doesn't check or update the database
as it assumes that the
database is in sync with the detached object.
Syntax: lock(Object entity,LockMode lockMode)
Specified by: lock in interface HibernateOperations
Parameters:
entity - the persistent instance to lock
lockMode - the lock mode to obtain
Throws:
DataAccessException - in case of Hibernate errors
There are five kind of locks that can be obtained -
LockMode.WRITE : It is obtained when Hibernate updates an object or saves new object.
LockMode.UPGRADE : Hibernate obtains this lock when using the SELECT <String> FOR UPDATE SQL command.
LockMode.UPGRADE_NOWAIT : Hibernate obtains this lock when using the SELECT <String> FOR UPDATE SQL command under the Oracle database server.
LockMode.READ : Hibernate obtains this lock either at the user's request or when neede for reading an object.
LockMode.NONE : Hibernate obtains this lock when a transaction finishes or during the start of a call to update() or saveOrUpdate().
Example : In this example we are updating record of student and using lock method to update record.
Here is main class code -
package net.roseindia.main;
import net.roseindia.table.Student;
import net.roseindia.util.HibernateUtil;
import org.hibernate.HibernateException;
import org.hibernate.LockMode;
import org.hibernate.Session;
import org.hibernate.Transaction;
public class HibernateUpdate {
public static void main(String args[]) {
Session session = HibernateUtil.getSessionFactory().openSession();
Transaction transaction = session.beginTransaction();
int roll = 5;
Student student = (Student) session.get(Student.class, roll);
try {
session.lock(student, LockMode.UPGRADE); // Using lock()
student.setCourse("Hibernate");
//session.update(student);
//session.saveOrUpdate(student);
session.merge(student);
transaction.commit();
System.out.println("Update Successfully");
session.close();
} catch (HibernateException e) {
e.printStackTrace();
}
}
}
Output :
Hibernate: select student0_.roll_no as roll1_0_0_, student0_.course as course0_0_, student0_.name as name0_0_ from student student0_ where student0_.roll_no=? Hibernate: select roll_no from student where roll_no =? for update Hibernate: update student set course=?, name=? where roll_no=? Update Successfully
