Your observation is correct – you can not have children of the same class.
My hunch is that it is due to the implementation of the Key class.
Each child Key holds reference to parent key/id. In theory it should be possible to have child of the same type, but I think current implementation does not allow it. Maybe to safeguard for infinite loop where you make same object child and parent……

Tomas

could you help me a bit if you have time?
yesterday I was trying to model a simple forum comments. Just a
comments which you can add more comments to.
So, the approximation of the entity is like this:
——————————————————————-
@PersistenceCapable (detachable = “true”, identityType =
IdentityType.APPLICATION)
public class CommentEntity {

@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
private Key key;

@Persistent
private String category;

@Persistent
private String commentDate;

@Persistent
private String userName;

@Persistent
private String commentBody;

@Persistent
private List children = new
ArrayList();

getters/setters/etc.
}

DataNucleus enhancement goes ok, no errors in the console.
Call of the pm.makePersistent() goes without any exceptions for such
entity.
BUT IT IS NOT PERSISTED.

I found out that problem is in “children” property. And the problem is
it’s a list of objects of the same class as the parent entity. If I
comment that property declaration the entity is persisted. Also if I
change the type of the child entities to some new class (not extending
the CommentEntity) it also gets persisted.

So my suspicion is that JDO (or GAE JDO impl) does not allow child
entities to be of the same class. Is it correct? Maybe I’m missing
something essential? Please advice.

thanks,
Tomas

i have been trying to persist a object with arraylist of objects (1-many relationship) however i always ran into some problem or other. and finally decided to use the example here … but again ran into a problem .. the error is

Caused by: java.lang.IllegalArgumentException: addresses: test.shared.Address is not a supported property type.

I am using the following code to persist the object person with addresses

ArrayList aa = new ArrayList();
aa.add(new Address(“123 sasdf”, “”, “Some City”, “AZ”, “93923-2321″));
aa.add(new Address(“23432 asdf”, “Appt 34″, “Another City”, “AZ”, “43434-4432″));
ArrayList parray = new ArrayList();
Person p = new Person();
p.setName(“VVVVVVV”);
p.setAge(23);
p.setGender(‘m’);
p.setAddresses(aa);
PersistenceManager pm = PMF.get().getPersistenceManager();
pm.makePersistent(p);
pm.close();

by the looks of it … i am sure there is something very simple which i am missing but not able to put a finger to it.

Please help…

I already implemented this in that way.
I see those guys also got this problem trying to implement comments )))) Fun.

Alex

could you help me a bit if you have time?
yesterday I was trying to model a simple forum comments. Just a
comments which you can add more comments to.
So, the approximation of the entity is like this:
——————————————————————-
@PersistenceCapable (detachable = “true”, identityType =
IdentityType.APPLICATION)
public class CommentEntity {

@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
private Key key;

@Persistent
private String category;

@Persistent
private String commentDate;

@Persistent
private String userName;

@Persistent
private String commentBody;

@Persistent
private List children = new
ArrayList();

getters/setters/etc.
}

DataNucleus enhancement goes ok, no errors in the console.
Call of the pm.makePersistent() goes without any exceptions for such
entity.
BUT IT IS NOT PERSISTED.

I found out that problem is in “children” property. And the problem is
it’s a list of objects of the same class as the parent entity. If I
comment that property declaration the entity is persisted. Also if I
change the type of the child entities to some new class (not extending
the CommentEntity) it also gets persisted.

So my suspicion is that JDO (or GAE JDO impl) does not allow child
entities to be of the same class. Is it correct? Maybe I’m missing
something essential? Please advice.