I'm designing a new app based on JPA/Hibernate, Spring and Wicket. The distinction between the DAO and Service layers isn't that clear to me though. According to Wikipedia, DAO is
an object that provides an abstract interface to some type of database or persistence mechanism, providing some specific operations without exposing details of the database.
I was wondering whether a DAO could contain methods that don't really have to do much with data access, but are way easier executed using a query? For example "get a list of all airlines that operate on a certain set of airports"? It sounds to me to be more of a service-layer method, but I'm not sure if using JPA EntityManager in the service layer is an example of good practice?