A very simple newbie question: I'm using Hibernate 3. For every class I specified an unique identifier via the id tag in my mapping.
Do I have to include this identifier (named id) as an attribute in each class or isn't that needed?
In all the Hibernate tutorials I read they do that but it would be easier to forget it ;-)

I’m sitting in the same boat, I can put the column in the database and in the mapping but I got the classes given to me, I may not change them and not all the classes have a id field in them so I would like to just leave it out but I am sure that hibernate use these id's to retrieve the classes somehow. As you all can probably see, I’m a newbie as well.

this is not mandatory but lot's of cool/useful features rely on an explicit id property