[appengine-java] Re: hard time modeling my database
So you are worried that a user will be deleted and his key will still be linked to the book? You can't rely on the database to do that work for you. You can do this two ways, worry about it, and when you delete a user, make sure you delete it's key from every book. Or don't worry about it. If you do your queries right, having a non existent user stored in a book won't cause any problems. But I would recommend removing it when a user gets deleted. On Feb 7, 3:11 pm, Arjan arjan.br...@gmail.com wrote: Will, Thanks for the hint. When i use the User key (a String) as the reference from the Book to the User object, that would mean that the referential integrity is not enforced by the database. I understand that it would work, but it feels kind of strange. Is there a way to maintain the referential integrity on between the classes? Regards. -- You received this message because you are subscribed to the Google Groups Google App Engine for Java group. To post to this group, send email to google-appengine-java@googlegroups.com. To unsubscribe from this group, send email to google-appengine-java+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-appengine-java?hl=en.
[appengine-java] Re: hard time modeling my database
Will, Thanks for the hint. When i use the User key (a String) as the reference from the Book to the User object, that would mean that the referential integrity is not enforced by the database. I understand that it would work, but it feels kind of strange. Is there a way to maintain the referential integrity on between the classes? Regards. -- You received this message because you are subscribed to the Google Groups Google App Engine for Java group. To post to this group, send email to google-appengine-java@googlegroups.com. To unsubscribe from this group, send email to google-appengine-java+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-appengine-java?hl=en.
[appengine-java] Re: hard time modeling my database
You want to store the Key of the User not the actual User. If you
store the User you are creating an owned relationship. This means
that the user can only be owned by one book. What you want is an
unowned relationship, which means storing the keys. Then your query
stays the same except you will need to add query.import(import Key)
--- not the exact syntax
On Feb 6, 5:04 pm, Arjan arjan.br...@gmail.com wrote:
Hi all,
It seems like i am doing this the wrong way and the datastore is giving me a
hard time making queries.
I've got a my own User class in my application and there is a Book class in
the application.
Now the Book class has an owner and a write attribute.
@Entity
class User {
@Id
private String email;
}
@Entity
class Book {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Key key;
private User owner;
private User writer;
}
I want to search the store for all owned books (on the users myPage)
Query query = getEntityManager().createQuery(SELECT b FROM Book b WHERE
b.owner == :owner);
query.setParameter(owner, owner);
ListBook books = query.getResultList();
Now the datastore is throwing ugly things to me like Key of parameter value
does not have a parent.
I'm realy lost here. Could anyone explain to me how i could solve this?
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