I've always wanted to know How can I update an entity effectively in hibernate just as by using SQL.

For example : I have a product entity , has a field name createTime , when I use session.saveOrUpdate(product) ; I have to get this field from database and then set to product then update , actually whenever I use session.saveOrUpdate() , I updated ALL fileds , even if I just need update only one field. but most time the value object we passed to DAO layer can't contain all fileds information , like the createDate in Product , we seldom need to update this field. How to just update selected fields ? Of course I can use HQL , but that will separate save and update logic .

It would be better If Hibernate has a method like this :

session.updateOnlyNotNullFields(product);

How can I do this in Hibernate ?