Question

Can a service-layer object “service” a DAO-layer object? Or is does this violate the integrity of a properly layered architecture?

e.g.,

class MyService {

}

class MyDao {
     private MyService myService;
}

Answer 1

I wouldn’t do it. DAOs ought to deal with databases; services manage other services and DAOs to fulfill their use cases. It’d be better to have the service call the DAO and any other services that are required.

You risk a circular dependency with this arrangement.