<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 2.0//EN"

"http://hibernate.sourceforge.net/hibernate-configuration-2.0.dtd">

<hibernate-configuration>

    <!-- a SessionFactory instance listed as /jndi/name -->
    <session-factory>

        <!-- properties -->
        <property name="show_sql">true</property>
        <property name="dialect">net.sf.hibernate.dialect.PostgreSQLDialect</property>
       
        <property name="connection.driver_class">org.postgresql.Driver</property>
        <property name="connection.url">jdbc:postgresql://localhost/db</property>
        <property name="connection.username">name</property>
        <property name="connection.password">password</property>
        <property name="connection.pool_size">3</property>
        <property name="max_fetch_depth">1</property>
        <property name="jdbc.batch_size" >0</property>
        <property name="connection.isolation">2</property>
        <!--
        <property name="transaction.factory_class">
            net.sf.hibernate.transaction.JTATransactionFactory
        </property>
        <property name="jta.UserTransaction">java:comp/UserTransaction</property>
        -->

        <!-- mapping files -->
        <mapping resource="domain/IntProperties.hbm.xml"/>
                                         
    </session-factory>

</hibernate-configuration>

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
   "-//Hibernate/Hibernate Mapping DTD 2.0//EN"
   "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">

<hibernate-mapping>

   <class
      name="domain.IntProperties"
      table="int_properties"
      lazy="true"
      optimistic-lock="version"
   >
   
      <id name="id" type="long" column="id">
         <generator class="native"/>
      </id>
      
      <version name="version"      column="version"    type="long" />
      
      <property name="name" column="name" type="string"/>
      <property name="value"  column="value" type="int"/>
      
   
   </class>

</hibernate-mapping>

package main;

import net.sf.hibernate.HibernateException;
import net.sf.hibernate.Session;




import org.apache.log4j.Logger;

import util.HibernateUtil;
import domain.*;

public class IntPropertiesMain
{
   private static Logger log = Logger.getLogger(IntPropertiesMain.class);

   private boolean       updated;

   public void readAndUpdate1() throws HibernateException
   {
      Session s = HibernateUtil.getSession();
      HibernateUtil.beginTransaction();
      int currentValue;

      // My table on has one row in it, so I can use .uniqueResult()
      IntProperties p = (IntProperties) s.createQuery("from IntProperties").uniqueResult();
     
      currentValue = p.getValue();
      //p.setValue(currentValue*2);
      // Un-comment this line to set to to its original value.
      p.setValue(currentValue);
     
      synchronized (this)
      {
         while (updated == false)
         {
            try
            {
               log.info("Waiting for another thread to do update");
               wait();
            }
            catch (InterruptedException e)
            {
               log.error(e.getMessage(), e);
            }
         }
         s.save(p);
         HibernateUtil.commitTransaction();
         s.close();
         updated = false;
         notifyAll();
      }
   }

   public void readAndUpdate2() throws HibernateException
   {
      Session s = HibernateUtil.getSession();
      HibernateUtil.beginTransaction();
     
      // My table on has one row in it, so I can use .uniqueResult()
      IntProperties p = (IntProperties) s.createQuery("from IntProperties").uniqueResult();
      int currentValue;
     
      currentValue = p.getValue();
      p.setValue(currentValue*3);

      synchronized (this)
      {
         s.save(p);
         HibernateUtil.commitTransaction();
         s.close();
         updated = true;
         notifyAll();
      }
   }

   public static void main(String[] args) throws Exception
   {
      final IntPropertiesMain pt = new IntPropertiesMain();

      Runnable r1 = new Runnable()
      {
         public void run()
         {
            try
            {
               pt.readAndUpdate1();
            }
            catch (HibernateException e)
            {
               log.error(e.getMessage(), e);
               e.printStackTrace();
            }
         }
      };

      Runnable r2 = new Runnable()
      {
         public void run()
         {
            try
            {
               pt.readAndUpdate2();
            }
            catch (HibernateException e)
            {
               log.error(e.getMessage(), e);
               e.printStackTrace();
            }
         }
      };

      Thread t1 = new Thread(r1);
      t1.setName("User1Thread");
      t1.start();
      log.debug("Waiting a few seconds to do 2nd update");
      Thread.sleep(3*1000);
      Thread t2 = new Thread(r2);
      t2.setName("User2Thread");
      t2.start();
   }
}