I was getting NullPointer exception with null clob, and the following 
is my fix,

<code>
   public Object nullSafeGet(ResultSet rs, String[] names, Object 
owner)
         throws HibernateException, SQLException {
      Clob clob = rs.getClob(names[0]);
      return (clob==null? null :clob.getSubString(1, (int) clob.length
()));
   }
</code>