title: why to use session.beginTransaction & transaction.commit
body: <p>Hibernate:
  If any Transient object was added into hibernate session, why can't hibernate persist it(after its dirty checking)  when i close the session. </p>
  
  <p>Is there any such of kind of option available.
  Also, if such option exists, then why we are beginning a transaction &amp; saying it  to commit. (session.beginTransaction() ) </p>
  
  <p>what functionality that transaction.commit() does can also be done once we say session.close() right? 
  Kindly any one explain me about this. </p>