Question

I’m getting my feet wet with persistence and Objectify. I’d like some guidance on assigning a Parent key. My specific questions are in all caps. Thanks.
(The sample model below contains an AppUser and a Video. The idea is like YouTube; a user creates videos that belong to him/her.)

@Entity
class Video{
// QUESTION 1: SHOULD THIS CLASS HAVE ONLY 1 KEY FIELD IF I WANT A 
PARENT RELATIONSHIP WITH AppUser, AND TYPE IS Key<AppUser> ?
@Parent Key<AppUser> owner;
@Id private Long id;

protected Video(){}
protected Video(User u){ // GAE User object     
    AppUser au = ofy().load().type(AppUser.class).filter("userId",u.getUserId()).first().get();

    // QUESTION 2: WHICH WAY IS RIGHT (TO ASSIGN PARENT KEY)?
    this.owner = Key.create(au.getKey(),AppUser.class,au.getId()); 
    // or:
    // owner = au.getKey();
    // or:
    // owner = au;
}
}

@Entity
public class AppUser {
@Id private String userId;

// QUESTION 3: DO ALL CLASSES REQUIRE A KEY FIELD?
private Key<AppUser> key;

protected AppUser(){}
protected AppUser(User u){// GAE User object    
    this.userId = u.getUserId();
}

public String getId(){
    return userId;
}

public Key<AppUser> getKey(){
    // QUESTION 4: IS THIS THE CORRECT WAY TO RETURN THE KEY? 
    // WOULD THAT IMPLY I NEED TO EXPLICITLY ASSIGN A VALUE TO FIELD key?

    return this.key;

    // THE ALTERNATIVE WOULD BE TO CREATE A KEY 
AND RETURN IT RIGHT? (THEN I CAN EXCLUDE FIELD key?)
    // return Key.create(AppUser.class, userId);
}
}

Answer 1

Answering my own question based on further knowledge:

1. Normally if a parent relationship is desired, one Key is fine. I can’t see why another Key field would be required.

2. I don’t think there’s 1 right way to assign a value to the @Parent Key. Using this seems to work:

   this.parent = Key.create(instanceOfParent);

3. All classes do not REQUIRE a key field. Use when needed.
4. There’s no one right way to return a Key, both examples could work.