I have the book "Hibernate in Action". I finally got hibernate configured to work but now my understanding from the book differs from what I see happening when I run the application. I thought that when I created a new User object that it would be persisted without me having to call session.save(user) because these columns are specified in file User.hbm.xml. I noticed that when I call session.save(user) it saves a row in the Users table. If I don't call it then then that table has 0 rows. I should note that I have the following in my configuration...





Hibernate version:
3.0

Mapping documents:
User.hbm.xml:


Code between sessionFactory.openSession() and session.close():
Session session = sessions.openSession();
Transaction tx = session.beginTransaction();
User user = new User();
user.setUsername(username);
user.setPassword(password);
//session.save(user); // why do I need this???
tx.commit();
session.close();

Full stack trace of any exception that occurs:
None

Name and version of the database you are using:
My SQL 4.1.9

The generated SQL (show_sql=true):

Debug level Hibernate log excerpt:

The object cannot even be handled by Hibernate until you give it a reference to it. There is not some magic instrumentation that hibernate puts in your classes to make them be "persistent". That is one of the attractions of hibernate for me, in particular. It means that the beans I use to persist to the database can also be used outside of the context of a session and therefore passed to layers of my application that know nothing about hibernate or that there is a database anywhere around.

Read your code again, at what point does a hibernate API get a hold of a reference to your newly created object? Not until you call session.save(). Up to that point, your object is just a POJO.

Hope this helps clear things up.

That makes a lot of sense actually. Thank you for helping my Hibernate newbie self out. :)