What is different between HQL and Criteria Queries. Where could be used HQL and Where could be used Criteria Queries.

(I think Criteria Queries is very easy for complex query?)

Thank you!

Criteria queries are best used where you do not know which query parameters will be selected. For example: if you had a list of books, you could provide a screen which allowed the user to search for a book by the author, ISBN, title, date published, publisher, etc. In HQL you would have to build a string containing the query. That is doable, but a also a pain. With the criteria, you just add restrictions to the query criteria which correspond to the parameters actually filled in by the user.

I would also add that Criteria queries can be less flexible than HQL. I greatly prefer them over HQL, but I have run in to several places where bugs or simple lack of functionality preclude using the Criteria API. Try it, but know that you may not be able to make it do what you need.