When and how to close a hibernate session?

Hi,

I am a newbie in hibernate. Following code is from Netbeans introducing how to use hibernate in visual web,
http://www.netbeans.org/kb/61/web/hibernate-vwp.html

My first question is when should I close the session. It did not mention in the online doc.

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private void buildPersonOptions() {
    List<Person> personList = null;
    try{
        Session session = HibernateUtil.getSessionFactory().getCurrentSession();
        Transaction tx = session.beginTransaction();
        Query q = session.createQuery("from Person");
        personList = (List<Person>) q.list();

    } catch(Exception e) {
        e.printStackTrace();
    }

    personOptions = new Option[personList.size()];
    int i=0;
    for(Person person : personList) {
        Option opt = new Option(person.getPersonId(), person.getName());
        personOptions[i++] = opt;
    }
}



Second question, I have create a visual web project using hibernate. Following is the part of the code in SessionBean1.java

protected void updateCurrentEmp(){
       
        List<CurrentEmpPrb> currentEmpList = null;
        List<Prb> availablePrbList = null;
        int prbStatus = 0;
     
        try{
           
            Transaction tx = sessionTest.beginTransaction();
            Query q = sessionTest.createQuery("from CurrentEmpPrb e where e.lanId = ?");
            String id = ((LanId) getBean("LanId")).getId();
            q.setString(0,id);
            currentEmpList = (List<CurrentEmpPrb>)q.list();
            tx.commit();
            //session.close();
        }catch(Exception e){
            e.printStackTrace();
        }finally{
           
        }
     
        if (currentEmpList.size()!=0){
            currentEmpOptions = new Option[currentEmpList.size()];
            int i=0;
            for(CurrentEmpPrb currEmployee : currentEmpList){
                Option opt = new Option(currEmployee.getCompany_EmployeeId      (),currEmployee.getCompany_EmployeeId());
                currentEmpOptions[i++] = opt;
            }
       
            currentEmp = currentEmpList.get(0);
       
               
            if (currentEmp.getEmp().getIsManager().longValue()==1){
                setCurrentEmpCategory("mngrView");
            }else{
                currentEmp.getEmp().getEmpPrbDetl().getEmpId();
             .......
            }
       else{
       .......
       }
}
I have noticed that I can not put 'sessionTest.close()' in try{} section, otherwise I will get a 'could not initialize proxy - no Session' exception because of lazy = 'true'. In this case, when should I close the session and how to achieve that?

Sorry for my poor english.

Thanks in advance!