Welcome to your first schooling in Hibernate.
The
word transaction can be literally defined as a "unit of work." Is connecting to a database, querying its data, and getting back some information work? I'm sure the database would think so.
So yes, you always need a transaction. You are always doing work.
Now, when we think of transactions, we often think of the ACID properties of a transaction, and rolling things back, and commits, and stuff like that, and you certainly don't need all that with a read, or something simple, but that doesn't mean you're not transacting with the database.
So yes, you always need a transaction.
A person named Christian Bauer, someone who might know a little bit about Hibernate, wrote this about your very question:
I did a training two weeks ago and all 12 people said "No" when I asked "are database transactions mandatory?". We have a long way...
Do We Always Need A Transaction? Tutorial: How to Save Data to the Database Using Hibernate and JPA -Cameron McKenzie