Transaction tx =  null ;
 try  {
tx = sess.beginTransaction();
// do some work
...
tx.commit();
}
 catch  (RuntimeException e) {
 if  (tx !=  null ) tx.rollback();
 throw  e; // or display error message
}
 finally  {
sess.close();
}

 public   void  increasePriceOfAllProductsInCategory( final  String category) {
 this .transactionTemplate.execute( new  TransactionCallbackWithoutResult() {
 public   void  doInTransactionWithoutResult(TransactionStatus status) {
List productsToChange =  this .productDao.loadProductsByCategory(category);
// do the price increase...
}
}
);
}

com.mycoolwebsite-|
                  +-BOL-|
                        MyService.java
                        MyServiceImpl.java
                        +-DAO-|
                              MyDao.java
                              +-Hibernate-|
                                          MyDaoHibernate.java