Hi,
I wrote an JDO object child relationship (code given below) where I want
store "subclass objects of an Abstract base class" as child of a Parent
object keeping field type of the base abstract class only. All the objects
are getting saved properly; if I fetch a single parent object using
getObjectById method then child object gets fetched but if try to fetch
whole list of it (6-7 entities) then child objects do not get fetched. I
know I am fundamentally wrong somewhere but even after giving it a lot of
effort I couldn't find what to do to make it work.
============ Parent Object Class ==============
@PersistenceCapable(identityType = IdentityType.APPLICATION)
public class Block implements Serializable {
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
private Long block_id;
*...@persistent(defaultFetchGroup = "true")
private BlockModule block_module;*
....
....
============= Abstract base class & child class ============
@PersistenceCapable(identityType = IdentityType.APPLICATION)
public abstract class *BlockModule *implements Serializable {
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
protected Key key;
public abstract Key getKey();
public abstract String getTitle(HttpServletRequest req);
public abstract String getContent(HttpServletRequest req);
}
@PersistenceCapable(identityType = IdentityType.APPLICATION)
public class BlockTextHTML extends BlockModule{
@Persistent
private String block_title;
@Persistent
private String block_content;
....
....
and getting following warning on console
Sep 27, 2009 5:53:47 AM org.datanucleus.store.appengine.MetaDataValidator
warn
WARNING: Meta-data warning for antshpra.Block.block_module: The datastore
does not support joins and therefore cannot honor requests to place child
objects in the default fetch group. The field will be fetched lazily on
first access. You can modify this warning by setting the
datanucleus.appengine.ignorableMetaDataBehavior property in your config. A
value of NONE will silence the warning. A value of ERROR will turn the
warning into an exception.
Someone please tell me where I am wrong and/or what else I should add ....
Thanks.
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