I have read the book "Java Persistence with Hibernate" and studied the CaveatEmptor Native code.

But I have a question.

In order to save a CategorizedItem I need to do this:

CategorizedItem cItem = new CategorizedItem("Scott", Category, Item);

CategorizedItemDao.makePersistent(cItem)



But in order to delete a CategorizedItem I need to do this:
Category.getCategorizedItems().remove(cItem)

BTW, do I need to save the category then again, in order to delete the categorized item?

My Question is:
Is this efficient? Because when I have lots of items in my category, then all items are read from the database when I do: Category.getCategorizedItems()

Why can't I just do: CategorizedItemDao.makeTransient(cItem);
I think this is much simpler.

Of course you can do that but then the Category has outdated collection references in-memory, which will lead to other problems down the road. It can also conflict with any cascading options (e.g. if on category.categorizedItems() is cascading persistence enabled Hibernate wouldn't know if it should now save it or remove it).

If you have a reference to an entity in a collection, and that collection belongs to an instance which is in-memory, you need to update the collection by removing the reference when the entity is removed.

Yes I understand what you mean.

But when I add a categorized item and I save it like this:

CategorizedItemDao.makePersistent(cItem), and I refresh the page again then the category is loaded again and has the new CategorizedItem in it.
Or am I wrong?

I don't fully understand when Category is in memory. In my opinion Category is only in memory in the same unit of work. After the unit of work is closed, Category is not in memory again after the page has been rendered.

Or is the Category still in memory after the webpage has been rendered?

I have no idea what is in your memory because I don't know what you are doing.