How to know that which user added or edited something on my website

My professor gave me a task to make function which tells him that which user is adding or editing the data on his website using java, spring, hibernate. he doesn't provided me any code and he just told me what i wrote above and i have no idea ho to do that. Can any well provide me sample or any help from anyone will be highly appreciated. sorry i am just an starter so please forgive me if my question is foolish. Thanks in advance