...
    public List<Parent> getChilds(Integer id1) {
    	try {
	    	session = HibernateUtil.getSessionFactory().openSession();
	    	parent = (Parent)session.get(Parent.class, id1);
		} finally {
		      if(session != null && session.isOpen()) {
		        session.close();
		      }    
		}
        return parent.getChildList();
    }

...

...
List<Childs> l = dao.getChilds(identifier);
...
.....l.size().............

...
public class HibernateSessionRequestFilter implements Filter {
    private static final Logger logger = Logger.getLogger(HibernateSessionRequestFilter.class);
    private SessionFactory sf;

    public void doFilter(ServletRequest request,
                         ServletResponse response,
                         FilterChain chain)
            throws IOException, ServletException {
        try {
            sf.getCurrentSession().beginTransaction();
            chain.doFilter(request, response);
            sf.getCurrentSession().getTransaction().commit();
        } catch (StaleObjectStateException staleEx) {
        	logger.error(staleEx.getMessage(), staleEx);
            throw staleEx;
        } catch (Throwable ex) {
        	logger.error(ex.getMessage(), ex);
            try {
                if (sf.getCurrentSession().getTransaction().isActive()) {
                    sf.getCurrentSession().getTransaction().rollback();
                }
            } catch (Throwable rbEx) {
            	logger.error(rbEx.getMessage(), rbEx);
            }
            throw new ServletException(ex);
        }
    }
    public void init(FilterConfig filterConfig) throws ServletException {
        sf = HibernateUtil.getSessionFactory()
    }
    public void destroy() {    	
    }
}
...

...
            sf.getCurrentSession().beginTransaction();
            chain.doFilter(request, response);
            sf.getCurrentSession().getTransaction().commit();

...

...
HibernateUtil.getCurrentSession().beginTransaction();
chain.doFilter(request, response);
HibernateUtil.getCurrentSession().getTransaction().commit();
...
        finally {
	    	  HibernateUtil.closeSession();
        }
...

...
    public static void closeSession() throws HibernateException {
        try {
            Session s = (Session) threadSession.get();
            threadSession.set(null);
            if (s != null && s.isOpen()) {
                s.close();
            }
        } catch (HibernateException ex) {
            throw new HibernateException(ex);
        }
    }

...

...
    public static Session getCurrentSession() throws HibernateException {
        Session s = (Session) threadSession.get();
        try {
            if(s == null) {
            	s = getMarksistSessionFactory().openSession();
            }
            threadSession.set(s);
        } catch (HibernateException ex) {
            throw new HibernateException(ex);
        }
        return s;
    }

...

// business layer

...
HibernateUtil.getCurrentSession().beginTransaction();
chain.doFilter(request, response);
HibernateUtil.getCurrentSession().getTransaction().commit();
...
HibernateUtil.closeSession();
...

...
dao.save(e)
...

...
	public void save(E e) {
        session = HibernateUtil.getCurrentSession();
        session.save(e);
        }
...

...
e = dao.getEntity(id);
e.getChilds.add(child);
...     
dao.update(e) 
dao.save(child)
...

...
@Entity
@Cache(usage = org.hibernate.annotations.CacheConcurrencyStrategy.NONE)
@Table(name = "WAR_N_PEACE")
public class Book {
	@Id	
	@Column(name = "ID")
	private Integer id;

	@OneToMany(cascade = CascadeType.ALL,fetch=FetchType.LAZY,mappedBy="book")
	private List<Authors> authors = new ArrayList<Authors>();
...
}

@Entity
@Cache(usage = org.hibernate.annotations.CacheConcurrencyStrategy.NONE)
@Table(name = "Authors")
public class Authors {
	@Id
	@Column(name = "ID")
	private Integer id;

	@ManyToOne
	private Book book;
...	
}

Book book = new Book();
...
dao.save(book);

Потом где- то сформируем список авторов -
...
Book book = dao.getBook(id);
Author author = new  Author();
...
book.getAuthors().add(author); //<<<< список на каждое обращение создается заново