Hibernate: flush() and commit()

Question

Is it good practice to call org.hibernate.Session.flush() separately?

As said in org.hibernate.Session docs,

Must be called at the end of a unit of work, before commiting the transaction and closing the session (depending on flush-mode, Transaction.commit() calls this method).

Could you explain the purpose of calling flush() explicitely if org.hibernate.Transaction.commit() will do it already?

Answer 1

In the Hibernate Manual you can see this example

Session session = sessionFactory.openSession(); Transaction tx = session.beginTransaction();  for (int i = 0; i < 100000; i++) {     Customer customer = new Customer(...);     session.save(customer);     if (i % 20 == 0) { // 20, same as the JDBC batch size         // flush a batch of inserts and release memory:         session.flush();         session.clear();     } }  tx.commit(); session.close(); 

Without the call to the flush method, your first-level cache would throw an OutOfMemoryException

Also you can look at this post about flushing