Hi
  Could you please tell me the difference between commit(method of
Session) and flush(method of Transaction) in Hibernate?
 I read the book "Java Persistence with hibernate" which reference
to  DAO Pattern for JDK1.5.
 The main interface of the pattern is GenericDAO as below:

 public interface GenericDAO<T, ID extends Serializable> {
        T findById(ID id, boolean lock);
        List<T> findAll();
        List<T> findByExample(T exampleInstance,
        String... excludeProperty);
        T makePersistent(T entity);
        void makeTransient(T entity);
        void flush();
        void clear();
}

what me me puzzled is why it has no method commit? And when should I
call the method flush and when shuold I commit the transaction if I
use this pattern?
Thanks.