Hey,
I've attached some example code for reference:
public class FooObject implements Serializable
{
private final String name;
public FooObject(String name)
{
this.name = name;
}
public String toString()
{
return name;
}
}
@PersistenceCapable
public class Entity
{
@Element(serialized="true")
List<FooObject> foos = new ArrayList<FooObject>();
public void addFoo(FooObject foo)
{
foos.add(foo);
}
public List<FooObject> getFoos()
{
return foos;
}
}
Please let me know if you see the problem.
Thanks!
On Jul 7, 10:30 am, laserjim <laser...@gmail.com> wrote:
> Hey,
>
> I agree that your comments above are true for serialized fields, but I
> can't find any documentation indicating such a behavior for
> collections (I assume "supported collections" here, as described in
> dataclasses#Collections). My understanding is that a collection
> should behave correctly (inserts, deletes, etc) unless the list its
> self is serialized. Can you provide a counter-example?
>
> With regards to the article Max Ross wrote (very good article by the
> way), the trick he used (where he made a copy in order to change the
> reference) was intended to "dirty" the state when a member is
> modified. My FooObjects are immutable, so I don't think this applies
> to me. Max Ross' article is completely consistent with my
> understanding of the documentation, but it's entirely possible I
> missed something, so let me know if this doesn't sound right to you.
>
> I BELIEVE the issue I'm running into is rooted in the exception I get
> when trying to persist a populated instance of the list: "FooObject is
> not a supported property type." I'm just not understanding why it
> isn't supported. I would have expected that any serializable object
> would be permitted, especially if the @Element(serialized="true")
> annotation is specified.
>
> Basically, I'm looking for a code fragment that demonstrates the
> persistence of a collection of (more than one) non-standard
> serializable objects.
>
> Any ideas?
>
> Thanks!
>
> On Jul 7, 5:05 am, "l.denardo" <lorenzo.dena...@gmail.com> wrote:
>
>
>
> > Hello,
> > I guess your problem is the behavior of serialized fields (including
> > collections of them, as far as I know), which is explained in Max
> > Ross's post.
> > Or something related to that.
>
> > Anyway, some property fields are marked as "updated" and hence saved
> > in the datastore only if you update the reference to the field, and
> > they're not updated if you just use modifiers to operate on them.
> > In practice, something like
>
> > ArrayList<Foo> list = "retrieve from datastore"
> > list.add(Foo foo)
> > close persistence manager
>
> > Does not modify the list in the datastore, so if it's saved as an
> > empty list at creation it remains empty.
> > Doing
>
> > ArrayList<Foo> list = "retrieve from datastore"
> > ArrayList copy = new ArrayList(list);
> > copy.add(Foo foo)
> > list = copy;
> > close PM
>
> > Usually makes everything work, since the original list field is marked
> > as "updated" and persisted.
> > As far as I know this is true both for serialized fields and for many
> > collections.
>
> > Regards
> > Lorenzo
>
> > On Jul 7, 1:28 pm, laserjim <laser...@gmail.com> wrote:
>
> > > Hello Lorenzo,
>
> > > Thanks, but perhaps my question wasn't clear. I'm trying to make a
> > > list of serialized objects, NOT a serialized list of objects.
>
> > > For instance, assuming FooObject implements Serializable...
>
> > > @Element(serialized="true)
> > > List<FooObject> foos = new ArrayList<FooObject>();
>
> > > Unfortunately, the list is always empty. Not quite sure why.
>
> > > Thanks!
>
> > > On Jul 7, 2:59 am, "l.denardo" <lorenzo.dena...@gmail.com> wrote:
>
> > > > If you are using a serialized field you must add the serialized="true"
> > > > clause to your annotation
>
> > > > @Persistent(serialized="true")
> > > > MySerializableObject serializable;
>
> > > > Also notice that JDO does not automatically detect if you update only
> > > > the inner fields of the object you save, so you must substitute it
> > > > with a copy to have it persisted.
> > > > See this post for a very good overview and an explanation of the fact
> > > > above:
>
> > > >http://groups.google.com/group/google-appengine-java/browse_thread/th...
>
> > > > Regards
> > > > Lorenzo
>
> > > > On Jul 7, 1:33 am, laserjim <laser...@gmail.com> wrote:
>
> > > > > Hello,
>
> > > > > I'm still trying to persist a list of serializable objects. I would
> > > > > expect this to be a standard collection as described
> > > > > here:http://code.google.com/appengine/docs/java/datastore/dataclasses.html...
>
> > > > > FooObject is serializable, but my attempt gave me an exception:
> > > > > FooObject is not a supported property type.
>
> > > > > Everything works as expected if I replace my serializable class
> > > > > (FooObject) with String.
>
> > > > > How can I persist my list of FooObjects using JDO?
>
> > > > > Thanks!
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