I have this strange behavior. I would appreciate if you can help me out. I have a user table in mysql database. In my application, I am creating new users. Here is the scenario: Let's say user X comes and creates an entry in database and ID (primary key, auto incremented) of 1 is assigned. Now the user X tries to create an account again; however, username is unique, so what happens is since the user enters the same user name, I get a duplicate hibernate exception which is correct behavior. But, when the user Y comes and creates an account, now the ID is 3 assigned instead of 2. I can replicate this every time. I tried session refresh, evict, and none of them is working. What is the problem? Thank you so much in advance for your time.

In my class, I have the following method:
public void registerUser(User user)throws Exception
{
try{

begin();
getSession().save(user);

commit();

logger.info("User created and entered in database");
SessionFactoryUtil.close();

}

catch( HibernateException e ){
rollback();

logger.info("exception is occured");
throw new Exception("Hibernate exception is occured");
}

}

}
package hibernate.domain.util;

import java.util.logging.Level;
import java.util.logging.Logger;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.AnnotationConfiguration;

public class SessionFactoryUtil {

private static final Logger log = Logger.getAnonymousLogger();
private static final ThreadLocal<Session> session = new ThreadLocal<Session>();
private static final SessionFactory sessionFactory =
new AnnotationConfiguration().configure().buildSessionFactory();

protected SessionFactoryUtil(){}

public static Session getSession()
{
Session session = (Session) SessionFactoryUtil.session.get();
if (session == null)
{
session = sessionFactory.openSession();
SessionFactoryUtil.session.set(session);
}
return session;
}

protected void begin()
{
getSession().beginTransaction();
}

protected void commit()
{
getSession().getTransaction().commit();
}

protected void rollback()
{
try
{
getSession().getTransaction().rollback();
}
catch( HibernateException e )
{
log.log(Level.WARNING,"Cannot rollback",e);
}

try
{
getSession().close();
}
catch( HibernateException e )
{
log.log(Level.WARNING,"Cannot close",e);
}
SessionFactoryUtil.session.set(null);
}

public static void close()
{
getSession().close();
SessionFactoryUtil.session.set(null);
}


}

It is expected behavior of MySQL auto-increment columns. At least for InnoDb tables. Quote from http://dev.mysql.com/doc/refman/5.1/en/ ... dling.html

Thank you so much for your help!