log4j:WARN No appenders could be found for logger (org.hibernate.cfg.Environment).
log4j:WARN Please initialize the log4j system properly.
org.hibernate.HibernateException: Not able to obtain connection
   at org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:117)
   at org.hibernate.jdbc.AbstractBatcher.prepareStatement(AbstractBatcher.java:93)
   at org.hibernate.jdbc.AbstractBatcher.prepareStatement(AbstractBatcher.java:86)
   at org.hibernate.jdbc.AbstractBatcher.prepareBatchStatement(AbstractBatcher.java:169)
   at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2047)
   at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2426)
   at org.hibernate.action.EntityInsertAction.execute(EntityInsertAction.java:51)
   at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:243)
   at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:227)
   at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:140)
   at org.hibernate.event.def.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:296)
   at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:27)
   at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:877)
   at revised.Main.main(Main.java:30)

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="revised">
  <class name="Logindetails" table="logindetails" optimistic-lock="none">
    <id name="userId" type="string" unsaved-value="null" column="UserId" length="40">
      <generator class="hilo"/>
    </id>
    <property name="password" type="string" column="Password" length="40"/>
    <one-to-one name="personaldetails" entity-name="revised.Personaldetails" cascade="save-update" foreign-key="personaldetails_ibfk_1" property-ref="userIdPersonal"/>
  </class>
</hibernate-mapping>

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="revised">
  <class name="Personaldetails" table="personaldetails" optimistic-lock="none">
    <id name="uniq" type="integer" unsaved-value="null" column="uniq">
      <generator class="assigned"/>
    </id>
    <property name="name" type="string" column="Name" length="40"/>
    <many-to-one name="userIdPersonal" entity-name="revised.Logindetails" cascade="save-update" foreign-key="personaldetails_ibfk_1">
      <column name="UserId_Personal" unique="true" index="IDX_personalDetails1" length="40"/>
    </many-to-one>
  </class>
</hibernate-mapping>

package revised;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.Transaction;
import revised.Personaldetails;

public class Main {

   /**
    * @param args
    */
   public static void main(String[] args) {
      // TODO Auto-generated method stub
      Session session=null;
      try
      {
            Configuration cfg=new Configuration();
            cfg.configure();
            SessionFactory factory = cfg.buildSessionFactory();
            session=factory.openSession();
            Transaction tx=session.beginTransaction();
            Personaldetails ps=new Personaldetails();
            ps.setUniq(new Integer(10));
            ps.setUserIdPersonal(ps.getUserIdPersonal());
            ps.setName("deva");
            tx.commit();
            session.save(ps);
            session.flush();
            session.close();
            System.out.println("Completed");
            
      }
         catch(Exception e)
         {
            e.printStackTrace(System.out);
            
         }
   }

}