Keep Coding

Say this is my classes
#Entity
public class Library{
...
}
#Entity
public class Book{
#Load
#Parent
#ApiResourceProperty(ignored = AnnotationBoolean.TRUE)
private Ref<Library> libraryRef;
#Ignore
private Library library;
}
I want to send List<Book> to the "android" client: I don't want the android client to get libraryRef but I want the client to get library
Here is the data access method I have now
public static List< Book > getAllBooks(){
return OfyService.ofy().load().type(Book.class).list();
}
My endpoint will just return List<Book> to android. I believe I have accomplished the first part: make sure datastore does not store library but libraryRef. But how do I accomplish the second part: make sure the client gets library?
I am sure it is not yet loaded. How do I make sure it is loaded? Do I have to use my own for-loop for iteration?

My advice for anyone working with code shared between client and server is to make a clean separation between your API objects and your domain objects. It's a little more work up front to make DTOs but it makes your whole system more flexible - if you want to change your domain objects, you don't risk breaking a zillion mobile phone apps that are on a slow (or nonexistant) upgrade cycle.