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Posted to users@wicket.apache.org by Jürgen Lind <Ju...@iteratec.de> on 2008/10/02 18:04:52 UTC
Problem understanding LoadableDetachableModel and ListViews
Hi there,
I have been struggling for some time now to understand how
LoadableDetachableModel and a ListView work together. The starting point
was Chapter 5.5.2 of "Wicket in Action" where it is recommended to provide
your own ItemModel if the underlying list changes frequently. To try out
how Wicket behaves without such a custom ItemModel, I wrote the following
Test:
<body>
<em wicket:id="listview">
<span wicket:id="label"></span><a wicket:id="delete">delete</a>
</em>
</body>
LoadableDetachableModel model = new LoadableDetachableModel() {
@Override
protected Object load() {
System.out.println("load");
return Arrays.asList(new TestItem[] {
new TestItem("a" + Math.random()),
new TestItem("b" + Math.random()),
new TestItem("c" + Math.random()) });
}
protected void onDetach() {
System.out.println("detach");
}
};
ListView listview = new ListView("listview", model) {
protected void populateItem(ListItem item) {
final TestItem itemModel = (TestItem) item.getModelObject();
item.add(new Label("label", itemModel.toString()));
item.add(new Link("delete") {
@Override
public void onClick() {
System.out.println("Delete " + itemModel);
}
});
}
};
add(listview);
Now, I would expect that when I hit the "delete" link, Wicket would call the
"load" Method of the LoadableDetachableModel before printing "Delete..." as the
default implementation will use the index and the list to determine the item to
delete. To my surprise, however, the "Delete..." message is printed with the
correct item and the "load" Method is called afterwards. In my understanding,
this contradicts the idea of the LoadableDetachableModel since Wicket seems to
have a copy of the original list somewhere so that it can determine the list
item on which the action was invoked before loading the underlying list.
Can someone spot my mistake?
Thanks,
J.
--
Dr. Jürgen Lind
iteratec GmbH Fon: +49 (0)89 614551-44
Inselkammerstrasse 4 Fax: +49 (0)89 614551-10
82008 Unterhaching Web: www.iteratec.de
Sitz und Registergericht der iteratec GmbH: München HRB 113 519
Geschäftsführer: Klaus Eberhardt, Mark Goerke, Inge Hanschke, Ralf Menzel
---------------------------------------------------------------------
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For additional commands, e-mail: users-help@wicket.apache.org
Re: Problem understanding LoadableDetachableModel and ListViews
Posted by Igor Vaynberg <ig...@gmail.com>.
using an LDM is best practice, big or small...
-igor
On Thu, Oct 2, 2008 at 11:09 AM, Jürgen Lind <Ju...@iteratec.de> wrote:
> I see. So for a small application with few users, the approach might be
> ok if I can live with a higher memory consumption. For larger
> applications, using a loadable detachable model would be preferable.
>
> Thank you for the clarification.
>
> J.
>
>
> Igor Vaynberg wrote:
>>
>> yes, there is a huge fundamental problem with your approach: you keep
>> the object reference which means the object is serialized instead of
>> being retrieved through a loadable detachable model.
>>
>> -igor
>>
>> On Thu, Oct 2, 2008 at 10:54 AM, Jürgen Lind <Ju...@iteratec.de>
>> wrote:
>>>
>>> Thanks for the explanation. Still, one questions remains: is there
>>> a fundamental problem with the first approach or is it ok to use
>>> the object directly?
>>>
>>> J.
>>>
>>> Igor Vaynberg wrote:
>>>>
>>>> final TestItem itemModel = (TestItem) item.getModelObject();
>>>>
>>>> ^ on this line you retrieve the object from the model, you then use
>>>> this reference inside the onclick() which is called during another
>>>> request. since you use the model object reference directly it is not
>>>> loaded from the model.
>>>>
>>>> my code, on the other hand, never keeps a direct reference to the
>>>> model object, instead it retrieves it from the model inside onclick()
>>>>
>>>> -igor
>>>>
>>>> On Thu, Oct 2, 2008 at 10:10 AM, Jürgen Lind <Ju...@iteratec.de>
>>>> wrote:
>>>>>
>>>>> Igor Vaynberg wrote:
>>>>>>
>>>>>> your link works on the object and not on the model, instead
>>>>>>
>>>>>> add(new link("delete", item.getmodel()) { onclick() {
>>>>>> delete(getmodelobject()); }});
>>>>>>
>>>>> Thank you for your quick reply.
>>>>>
>>>>> Well the code is roughly the same(?) as in Listing 5.12 of WiA and
>>>>> there
>>>>> a custom Model is used to illustrate the solution. However, I thought
>>>>> my
>>>>> test would show me the problem first... Using your code above, the
>>>>> effect is as expected, i.e. the "wrong" (new) item is returned to be
>>>>> deleted.
>>>>>
>>>>> Now, the question is, what is wrong with my first implementation?
>>>>> It would seem that the problem that is solved using a custom ItemModel
>>>>> does not even occur. Or does that code prevent wicket from effectively
>>>>> detaching model objects and should thus be avoided? What would be the
>>>>> best practice here?
>>>>>
>>>>>
>>>>> J.
>>>>>
>>>>>> -igor
>>>>>>
>>>>>> On Thu, Oct 2, 2008 at 9:04 AM, Jürgen Lind <Ju...@iteratec.de>
>>>>>> wrote:
>>>>>>>
>>>>>>> Hi there,
>>>>>>>
>>>>>>> I have been struggling for some time now to understand how
>>>>>>> LoadableDetachableModel and a ListView work together. The starting
>>>>>>> point
>>>>>>> was Chapter 5.5.2 of "Wicket in Action" where it is recommended to
>>>>>>> provide
>>>>>>> your own ItemModel if the underlying list changes frequently. To try
>>>>>>> out
>>>>>>> how Wicket behaves without such a custom ItemModel, I wrote the
>>>>>>> following
>>>>>>> Test:
>>>>>>>
>>>>>>> <body>
>>>>>>> <em wicket:id="listview">
>>>>>>> <span wicket:id="label"></span><a wicket:id="delete">delete</a>
>>>>>>> </em>
>>>>>>> </body>
>>>>>>>
>>>>>>>
>>>>>>> LoadableDetachableModel model = new LoadableDetachableModel() {
>>>>>>>
>>>>>>> @Override
>>>>>>> protected Object load() {
>>>>>>> System.out.println("load");
>>>>>>> return Arrays.asList(new TestItem[] {
>>>>>>> new TestItem("a" + Math.random()),
>>>>>>> new TestItem("b" + Math.random()),
>>>>>>> new TestItem("c" + Math.random()) });
>>>>>>> }
>>>>>>>
>>>>>>> protected void onDetach() {
>>>>>>> System.out.println("detach");
>>>>>>> }
>>>>>>>
>>>>>>> };
>>>>>>>
>>>>>>> ListView listview = new ListView("listview", model) {
>>>>>>> protected void populateItem(ListItem item) {
>>>>>>> final TestItem itemModel = (TestItem) item.getModelObject();
>>>>>>> item.add(new Label("label", itemModel.toString()));
>>>>>>> item.add(new Link("delete") {
>>>>>>>
>>>>>>> @Override
>>>>>>> public void onClick() {
>>>>>>> System.out.println("Delete " + itemModel);
>>>>>>> }
>>>>>>> });
>>>>>>> }
>>>>>>> };
>>>>>>>
>>>>>>> add(listview);
>>>>>>>
>>>>>>>
>>>>>>> Now, I would expect that when I hit the "delete" link, Wicket would
>>>>>>> call
>>>>>>> the
>>>>>>> "load" Method of the LoadableDetachableModel before printing
>>>>>>> "Delete..."
>>>>>>> as
>>>>>>> the
>>>>>>> default implementation will use the index and the list to determine
>>>>>>> the
>>>>>>> item
>>>>>>> to
>>>>>>> delete. To my surprise, however, the "Delete..." message is printed
>>>>>>> with
>>>>>>> the
>>>>>>> correct item and the "load" Method is called afterwards. In my
>>>>>>> understanding,
>>>>>>> this contradicts the idea of the LoadableDetachableModel since Wicket
>>>>>>> seems
>>>>>>> to
>>>>>>> have a copy of the original list somewhere so that it can determine
>>>>>>> the
>>>>>>> list
>>>>>>> item on which the action was invoked before loading the underlying
>>>>>>> list.
>>>>>>>
>>>>>>> Can someone spot my mistake?
>>>>>>>
>>>>>>> Thanks,
>>>>>>>
>>>>>>> J.
>>>>>>>
>>>>>>> --
>>>>>>> Dr. Jürgen Lind
>>>>>>> iteratec GmbH Fon: +49 (0)89 614551-44
>>>>>>> Inselkammerstrasse 4 Fax: +49 (0)89 614551-10
>>>>>>> 82008 Unterhaching Web: www.iteratec.de
>>>>>>>
>>>>>>> Sitz und Registergericht der iteratec GmbH: München HRB 113 519
>>>>>>> Geschäftsführer: Klaus Eberhardt, Mark Goerke, Inge Hanschke, Ralf
>>>>>>> Menzel
>>>>>>>
>>>>>>>
>>>>>>> ---------------------------------------------------------------------
>>>>>>> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
>>>>>>> For additional commands, e-mail: users-help@wicket.apache.org
>>>>>>>
>>>>>>>
>>>>>> ---------------------------------------------------------------------
>>>>>> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
>>>>>> For additional commands, e-mail: users-help@wicket.apache.org
>>>>>>
>>>>> --
>>>>> Dr. Jürgen Lind
>>>>> iteratec GmbH Fon: +49 (0)89 614551-44
>>>>> Inselkammerstrasse 4 Fax: +49 (0)89 614551-10
>>>>> 82008 Unterhaching Web: www.iteratec.de
>>>>>
>>>>> Sitz und Registergericht der iteratec GmbH: München HRB 113 519
>>>>> Geschäftsführer: Klaus Eberhardt, Mark Goerke, Inge Hanschke, Ralf
>>>>> Menzel
>>>>>
>>>>>
>>>>> ---------------------------------------------------------------------
>>>>> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
>>>>> For additional commands, e-mail: users-help@wicket.apache.org
>>>>>
>>>>>
>>>> ---------------------------------------------------------------------
>>>> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
>>>> For additional commands, e-mail: users-help@wicket.apache.org
>>>>
>>>
>>> --
>>> Dr. Jürgen Lind
>>> iteratec GmbH Fon: +49 (0)89 614551-44
>>> Inselkammerstrasse 4 Fax: +49 (0)89 614551-10
>>> 82008 Unterhaching Web: www.iteratec.de
>>>
>>> Sitz und Registergericht der iteratec GmbH: München HRB 113 519
>>> Geschäftsführer: Klaus Eberhardt, Mark Goerke, Inge Hanschke, Ralf Menzel
>>>
>>>
>>> ---------------------------------------------------------------------
>>> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
>>> For additional commands, e-mail: users-help@wicket.apache.org
>>>
>>>
>>
>> ---------------------------------------------------------------------
>> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
>> For additional commands, e-mail: users-help@wicket.apache.org
>>
>
> --
> Dr. Jürgen Lind
> iteratec GmbH Fon: +49 (0)89 614551-44
> Inselkammerstrasse 4 Fax: +49 (0)89 614551-10
> 82008 Unterhaching Web: www.iteratec.de
>
> Sitz und Registergericht der iteratec GmbH: München HRB 113 519
> Geschäftsführer: Klaus Eberhardt, Mark Goerke, Inge Hanschke, Ralf Menzel
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
> For additional commands, e-mail: users-help@wicket.apache.org
>
>
---------------------------------------------------------------------
To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
For additional commands, e-mail: users-help@wicket.apache.org
Re: Problem understanding LoadableDetachableModel and ListViews
Posted by Jürgen Lind <Ju...@iteratec.de>.
I see. So for a small application with few users, the approach might be
ok if I can live with a higher memory consumption. For larger
applications, using a loadable detachable model would be preferable.
Thank you for the clarification.
J.
Igor Vaynberg wrote:
> yes, there is a huge fundamental problem with your approach: you keep
> the object reference which means the object is serialized instead of
> being retrieved through a loadable detachable model.
>
> -igor
>
> On Thu, Oct 2, 2008 at 10:54 AM, Jürgen Lind <Ju...@iteratec.de> wrote:
>> Thanks for the explanation. Still, one questions remains: is there
>> a fundamental problem with the first approach or is it ok to use
>> the object directly?
>>
>> J.
>>
>> Igor Vaynberg wrote:
>>> final TestItem itemModel = (TestItem) item.getModelObject();
>>>
>>> ^ on this line you retrieve the object from the model, you then use
>>> this reference inside the onclick() which is called during another
>>> request. since you use the model object reference directly it is not
>>> loaded from the model.
>>>
>>> my code, on the other hand, never keeps a direct reference to the
>>> model object, instead it retrieves it from the model inside onclick()
>>>
>>> -igor
>>>
>>> On Thu, Oct 2, 2008 at 10:10 AM, Jürgen Lind <Ju...@iteratec.de>
>>> wrote:
>>>> Igor Vaynberg wrote:
>>>>> your link works on the object and not on the model, instead
>>>>>
>>>>> add(new link("delete", item.getmodel()) { onclick() {
>>>>> delete(getmodelobject()); }});
>>>>>
>>>> Thank you for your quick reply.
>>>>
>>>> Well the code is roughly the same(?) as in Listing 5.12 of WiA and there
>>>> a custom Model is used to illustrate the solution. However, I thought my
>>>> test would show me the problem first... Using your code above, the
>>>> effect is as expected, i.e. the "wrong" (new) item is returned to be
>>>> deleted.
>>>>
>>>> Now, the question is, what is wrong with my first implementation?
>>>> It would seem that the problem that is solved using a custom ItemModel
>>>> does not even occur. Or does that code prevent wicket from effectively
>>>> detaching model objects and should thus be avoided? What would be the
>>>> best practice here?
>>>>
>>>>
>>>> J.
>>>>
>>>>> -igor
>>>>>
>>>>> On Thu, Oct 2, 2008 at 9:04 AM, Jürgen Lind <Ju...@iteratec.de>
>>>>> wrote:
>>>>>> Hi there,
>>>>>>
>>>>>> I have been struggling for some time now to understand how
>>>>>> LoadableDetachableModel and a ListView work together. The starting
>>>>>> point
>>>>>> was Chapter 5.5.2 of "Wicket in Action" where it is recommended to
>>>>>> provide
>>>>>> your own ItemModel if the underlying list changes frequently. To try
>>>>>> out
>>>>>> how Wicket behaves without such a custom ItemModel, I wrote the
>>>>>> following
>>>>>> Test:
>>>>>>
>>>>>> <body>
>>>>>> <em wicket:id="listview">
>>>>>> <span wicket:id="label"></span><a wicket:id="delete">delete</a>
>>>>>> </em>
>>>>>> </body>
>>>>>>
>>>>>>
>>>>>> LoadableDetachableModel model = new LoadableDetachableModel() {
>>>>>>
>>>>>> @Override
>>>>>> protected Object load() {
>>>>>> System.out.println("load");
>>>>>> return Arrays.asList(new TestItem[] {
>>>>>> new TestItem("a" + Math.random()),
>>>>>> new TestItem("b" + Math.random()),
>>>>>> new TestItem("c" + Math.random()) });
>>>>>> }
>>>>>>
>>>>>> protected void onDetach() {
>>>>>> System.out.println("detach");
>>>>>> }
>>>>>>
>>>>>> };
>>>>>>
>>>>>> ListView listview = new ListView("listview", model) {
>>>>>> protected void populateItem(ListItem item) {
>>>>>> final TestItem itemModel = (TestItem) item.getModelObject();
>>>>>> item.add(new Label("label", itemModel.toString()));
>>>>>> item.add(new Link("delete") {
>>>>>>
>>>>>> @Override
>>>>>> public void onClick() {
>>>>>> System.out.println("Delete " + itemModel);
>>>>>> }
>>>>>> });
>>>>>> }
>>>>>> };
>>>>>>
>>>>>> add(listview);
>>>>>>
>>>>>>
>>>>>> Now, I would expect that when I hit the "delete" link, Wicket would
>>>>>> call
>>>>>> the
>>>>>> "load" Method of the LoadableDetachableModel before printing
>>>>>> "Delete..."
>>>>>> as
>>>>>> the
>>>>>> default implementation will use the index and the list to determine the
>>>>>> item
>>>>>> to
>>>>>> delete. To my surprise, however, the "Delete..." message is printed
>>>>>> with
>>>>>> the
>>>>>> correct item and the "load" Method is called afterwards. In my
>>>>>> understanding,
>>>>>> this contradicts the idea of the LoadableDetachableModel since Wicket
>>>>>> seems
>>>>>> to
>>>>>> have a copy of the original list somewhere so that it can determine the
>>>>>> list
>>>>>> item on which the action was invoked before loading the underlying
>>>>>> list.
>>>>>>
>>>>>> Can someone spot my mistake?
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>> J.
>>>>>>
>>>>>> --
>>>>>> Dr. Jürgen Lind
>>>>>> iteratec GmbH Fon: +49 (0)89 614551-44
>>>>>> Inselkammerstrasse 4 Fax: +49 (0)89 614551-10
>>>>>> 82008 Unterhaching Web: www.iteratec.de
>>>>>>
>>>>>> Sitz und Registergericht der iteratec GmbH: München HRB 113 519
>>>>>> Geschäftsführer: Klaus Eberhardt, Mark Goerke, Inge Hanschke, Ralf
>>>>>> Menzel
>>>>>>
>>>>>>
>>>>>> ---------------------------------------------------------------------
>>>>>> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
>>>>>> For additional commands, e-mail: users-help@wicket.apache.org
>>>>>>
>>>>>>
>>>>> ---------------------------------------------------------------------
>>>>> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
>>>>> For additional commands, e-mail: users-help@wicket.apache.org
>>>>>
>>>> --
>>>> Dr. Jürgen Lind
>>>> iteratec GmbH Fon: +49 (0)89 614551-44
>>>> Inselkammerstrasse 4 Fax: +49 (0)89 614551-10
>>>> 82008 Unterhaching Web: www.iteratec.de
>>>>
>>>> Sitz und Registergericht der iteratec GmbH: München HRB 113 519
>>>> Geschäftsführer: Klaus Eberhardt, Mark Goerke, Inge Hanschke, Ralf Menzel
>>>>
>>>>
>>>> ---------------------------------------------------------------------
>>>> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
>>>> For additional commands, e-mail: users-help@wicket.apache.org
>>>>
>>>>
>>> ---------------------------------------------------------------------
>>> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
>>> For additional commands, e-mail: users-help@wicket.apache.org
>>>
>>
>> --
>> Dr. Jürgen Lind
>> iteratec GmbH Fon: +49 (0)89 614551-44
>> Inselkammerstrasse 4 Fax: +49 (0)89 614551-10
>> 82008 Unterhaching Web: www.iteratec.de
>>
>> Sitz und Registergericht der iteratec GmbH: München HRB 113 519
>> Geschäftsführer: Klaus Eberhardt, Mark Goerke, Inge Hanschke, Ralf Menzel
>>
>>
>> ---------------------------------------------------------------------
>> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
>> For additional commands, e-mail: users-help@wicket.apache.org
>>
>>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
> For additional commands, e-mail: users-help@wicket.apache.org
>
--
Dr. Jürgen Lind
iteratec GmbH Fon: +49 (0)89 614551-44
Inselkammerstrasse 4 Fax: +49 (0)89 614551-10
82008 Unterhaching Web: www.iteratec.de
Sitz und Registergericht der iteratec GmbH: München HRB 113 519
Geschäftsführer: Klaus Eberhardt, Mark Goerke, Inge Hanschke, Ralf Menzel
---------------------------------------------------------------------
To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
For additional commands, e-mail: users-help@wicket.apache.org
Re: Problem understanding LoadableDetachableModel and ListViews
Posted by Igor Vaynberg <ig...@gmail.com>.
yes, there is a huge fundamental problem with your approach: you keep
the object reference which means the object is serialized instead of
being retrieved through a loadable detachable model.
-igor
On Thu, Oct 2, 2008 at 10:54 AM, Jürgen Lind <Ju...@iteratec.de> wrote:
>
> Thanks for the explanation. Still, one questions remains: is there
> a fundamental problem with the first approach or is it ok to use
> the object directly?
>
> J.
>
> Igor Vaynberg wrote:
>>
>> final TestItem itemModel = (TestItem) item.getModelObject();
>>
>> ^ on this line you retrieve the object from the model, you then use
>> this reference inside the onclick() which is called during another
>> request. since you use the model object reference directly it is not
>> loaded from the model.
>>
>> my code, on the other hand, never keeps a direct reference to the
>> model object, instead it retrieves it from the model inside onclick()
>>
>> -igor
>>
>> On Thu, Oct 2, 2008 at 10:10 AM, Jürgen Lind <Ju...@iteratec.de>
>> wrote:
>>>
>>> Igor Vaynberg wrote:
>>>>
>>>> your link works on the object and not on the model, instead
>>>>
>>>> add(new link("delete", item.getmodel()) { onclick() {
>>>> delete(getmodelobject()); }});
>>>>
>>> Thank you for your quick reply.
>>>
>>> Well the code is roughly the same(?) as in Listing 5.12 of WiA and there
>>> a custom Model is used to illustrate the solution. However, I thought my
>>> test would show me the problem first... Using your code above, the
>>> effect is as expected, i.e. the "wrong" (new) item is returned to be
>>> deleted.
>>>
>>> Now, the question is, what is wrong with my first implementation?
>>> It would seem that the problem that is solved using a custom ItemModel
>>> does not even occur. Or does that code prevent wicket from effectively
>>> detaching model objects and should thus be avoided? What would be the
>>> best practice here?
>>>
>>>
>>> J.
>>>
>>>> -igor
>>>>
>>>> On Thu, Oct 2, 2008 at 9:04 AM, Jürgen Lind <Ju...@iteratec.de>
>>>> wrote:
>>>>>
>>>>> Hi there,
>>>>>
>>>>> I have been struggling for some time now to understand how
>>>>> LoadableDetachableModel and a ListView work together. The starting
>>>>> point
>>>>> was Chapter 5.5.2 of "Wicket in Action" where it is recommended to
>>>>> provide
>>>>> your own ItemModel if the underlying list changes frequently. To try
>>>>> out
>>>>> how Wicket behaves without such a custom ItemModel, I wrote the
>>>>> following
>>>>> Test:
>>>>>
>>>>> <body>
>>>>> <em wicket:id="listview">
>>>>> <span wicket:id="label"></span><a wicket:id="delete">delete</a>
>>>>> </em>
>>>>> </body>
>>>>>
>>>>>
>>>>> LoadableDetachableModel model = new LoadableDetachableModel() {
>>>>>
>>>>> @Override
>>>>> protected Object load() {
>>>>> System.out.println("load");
>>>>> return Arrays.asList(new TestItem[] {
>>>>> new TestItem("a" + Math.random()),
>>>>> new TestItem("b" + Math.random()),
>>>>> new TestItem("c" + Math.random()) });
>>>>> }
>>>>>
>>>>> protected void onDetach() {
>>>>> System.out.println("detach");
>>>>> }
>>>>>
>>>>> };
>>>>>
>>>>> ListView listview = new ListView("listview", model) {
>>>>> protected void populateItem(ListItem item) {
>>>>> final TestItem itemModel = (TestItem) item.getModelObject();
>>>>> item.add(new Label("label", itemModel.toString()));
>>>>> item.add(new Link("delete") {
>>>>>
>>>>> @Override
>>>>> public void onClick() {
>>>>> System.out.println("Delete " + itemModel);
>>>>> }
>>>>> });
>>>>> }
>>>>> };
>>>>>
>>>>> add(listview);
>>>>>
>>>>>
>>>>> Now, I would expect that when I hit the "delete" link, Wicket would
>>>>> call
>>>>> the
>>>>> "load" Method of the LoadableDetachableModel before printing
>>>>> "Delete..."
>>>>> as
>>>>> the
>>>>> default implementation will use the index and the list to determine the
>>>>> item
>>>>> to
>>>>> delete. To my surprise, however, the "Delete..." message is printed
>>>>> with
>>>>> the
>>>>> correct item and the "load" Method is called afterwards. In my
>>>>> understanding,
>>>>> this contradicts the idea of the LoadableDetachableModel since Wicket
>>>>> seems
>>>>> to
>>>>> have a copy of the original list somewhere so that it can determine the
>>>>> list
>>>>> item on which the action was invoked before loading the underlying
>>>>> list.
>>>>>
>>>>> Can someone spot my mistake?
>>>>>
>>>>> Thanks,
>>>>>
>>>>> J.
>>>>>
>>>>> --
>>>>> Dr. Jürgen Lind
>>>>> iteratec GmbH Fon: +49 (0)89 614551-44
>>>>> Inselkammerstrasse 4 Fax: +49 (0)89 614551-10
>>>>> 82008 Unterhaching Web: www.iteratec.de
>>>>>
>>>>> Sitz und Registergericht der iteratec GmbH: München HRB 113 519
>>>>> Geschäftsführer: Klaus Eberhardt, Mark Goerke, Inge Hanschke, Ralf
>>>>> Menzel
>>>>>
>>>>>
>>>>> ---------------------------------------------------------------------
>>>>> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
>>>>> For additional commands, e-mail: users-help@wicket.apache.org
>>>>>
>>>>>
>>>> ---------------------------------------------------------------------
>>>> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
>>>> For additional commands, e-mail: users-help@wicket.apache.org
>>>>
>>> --
>>> Dr. Jürgen Lind
>>> iteratec GmbH Fon: +49 (0)89 614551-44
>>> Inselkammerstrasse 4 Fax: +49 (0)89 614551-10
>>> 82008 Unterhaching Web: www.iteratec.de
>>>
>>> Sitz und Registergericht der iteratec GmbH: München HRB 113 519
>>> Geschäftsführer: Klaus Eberhardt, Mark Goerke, Inge Hanschke, Ralf Menzel
>>>
>>>
>>> ---------------------------------------------------------------------
>>> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
>>> For additional commands, e-mail: users-help@wicket.apache.org
>>>
>>>
>>
>> ---------------------------------------------------------------------
>> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
>> For additional commands, e-mail: users-help@wicket.apache.org
>>
>
>
> --
> Dr. Jürgen Lind
> iteratec GmbH Fon: +49 (0)89 614551-44
> Inselkammerstrasse 4 Fax: +49 (0)89 614551-10
> 82008 Unterhaching Web: www.iteratec.de
>
> Sitz und Registergericht der iteratec GmbH: München HRB 113 519
> Geschäftsführer: Klaus Eberhardt, Mark Goerke, Inge Hanschke, Ralf Menzel
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
> For additional commands, e-mail: users-help@wicket.apache.org
>
>
---------------------------------------------------------------------
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For additional commands, e-mail: users-help@wicket.apache.org
Re: Problem understanding LoadableDetachableModel and ListViews
Posted by Jürgen Lind <Ju...@iteratec.de>.
Thanks for the explanation. Still, one questions remains: is there
a fundamental problem with the first approach or is it ok to use
the object directly?
J.
Igor Vaynberg wrote:
> final TestItem itemModel = (TestItem) item.getModelObject();
>
> ^ on this line you retrieve the object from the model, you then use
> this reference inside the onclick() which is called during another
> request. since you use the model object reference directly it is not
> loaded from the model.
>
> my code, on the other hand, never keeps a direct reference to the
> model object, instead it retrieves it from the model inside onclick()
>
> -igor
>
> On Thu, Oct 2, 2008 at 10:10 AM, Jürgen Lind <Ju...@iteratec.de> wrote:
>> Igor Vaynberg wrote:
>>> your link works on the object and not on the model, instead
>>>
>>> add(new link("delete", item.getmodel()) { onclick() {
>>> delete(getmodelobject()); }});
>>>
>> Thank you for your quick reply.
>>
>> Well the code is roughly the same(?) as in Listing 5.12 of WiA and there
>> a custom Model is used to illustrate the solution. However, I thought my
>> test would show me the problem first... Using your code above, the
>> effect is as expected, i.e. the "wrong" (new) item is returned to be
>> deleted.
>>
>> Now, the question is, what is wrong with my first implementation?
>> It would seem that the problem that is solved using a custom ItemModel
>> does not even occur. Or does that code prevent wicket from effectively
>> detaching model objects and should thus be avoided? What would be the
>> best practice here?
>>
>>
>> J.
>>
>>> -igor
>>>
>>> On Thu, Oct 2, 2008 at 9:04 AM, Jürgen Lind <Ju...@iteratec.de>
>>> wrote:
>>>> Hi there,
>>>>
>>>> I have been struggling for some time now to understand how
>>>> LoadableDetachableModel and a ListView work together. The starting point
>>>> was Chapter 5.5.2 of "Wicket in Action" where it is recommended to
>>>> provide
>>>> your own ItemModel if the underlying list changes frequently. To try out
>>>> how Wicket behaves without such a custom ItemModel, I wrote the following
>>>> Test:
>>>>
>>>> <body>
>>>> <em wicket:id="listview">
>>>> <span wicket:id="label"></span><a wicket:id="delete">delete</a>
>>>> </em>
>>>> </body>
>>>>
>>>>
>>>> LoadableDetachableModel model = new LoadableDetachableModel() {
>>>>
>>>> @Override
>>>> protected Object load() {
>>>> System.out.println("load");
>>>> return Arrays.asList(new TestItem[] {
>>>> new TestItem("a" + Math.random()),
>>>> new TestItem("b" + Math.random()),
>>>> new TestItem("c" + Math.random()) });
>>>> }
>>>>
>>>> protected void onDetach() {
>>>> System.out.println("detach");
>>>> }
>>>>
>>>> };
>>>>
>>>> ListView listview = new ListView("listview", model) {
>>>> protected void populateItem(ListItem item) {
>>>> final TestItem itemModel = (TestItem) item.getModelObject();
>>>> item.add(new Label("label", itemModel.toString()));
>>>> item.add(new Link("delete") {
>>>>
>>>> @Override
>>>> public void onClick() {
>>>> System.out.println("Delete " + itemModel);
>>>> }
>>>> });
>>>> }
>>>> };
>>>>
>>>> add(listview);
>>>>
>>>>
>>>> Now, I would expect that when I hit the "delete" link, Wicket would call
>>>> the
>>>> "load" Method of the LoadableDetachableModel before printing "Delete..."
>>>> as
>>>> the
>>>> default implementation will use the index and the list to determine the
>>>> item
>>>> to
>>>> delete. To my surprise, however, the "Delete..." message is printed with
>>>> the
>>>> correct item and the "load" Method is called afterwards. In my
>>>> understanding,
>>>> this contradicts the idea of the LoadableDetachableModel since Wicket
>>>> seems
>>>> to
>>>> have a copy of the original list somewhere so that it can determine the
>>>> list
>>>> item on which the action was invoked before loading the underlying list.
>>>>
>>>> Can someone spot my mistake?
>>>>
>>>> Thanks,
>>>>
>>>> J.
>>>>
>>>> --
>>>> Dr. Jürgen Lind
>>>> iteratec GmbH Fon: +49 (0)89 614551-44
>>>> Inselkammerstrasse 4 Fax: +49 (0)89 614551-10
>>>> 82008 Unterhaching Web: www.iteratec.de
>>>>
>>>> Sitz und Registergericht der iteratec GmbH: München HRB 113 519
>>>> Geschäftsführer: Klaus Eberhardt, Mark Goerke, Inge Hanschke, Ralf Menzel
>>>>
>>>>
>>>> ---------------------------------------------------------------------
>>>> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
>>>> For additional commands, e-mail: users-help@wicket.apache.org
>>>>
>>>>
>>> ---------------------------------------------------------------------
>>> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
>>> For additional commands, e-mail: users-help@wicket.apache.org
>>>
>> --
>> Dr. Jürgen Lind
>> iteratec GmbH Fon: +49 (0)89 614551-44
>> Inselkammerstrasse 4 Fax: +49 (0)89 614551-10
>> 82008 Unterhaching Web: www.iteratec.de
>>
>> Sitz und Registergericht der iteratec GmbH: München HRB 113 519
>> Geschäftsführer: Klaus Eberhardt, Mark Goerke, Inge Hanschke, Ralf Menzel
>>
>>
>> ---------------------------------------------------------------------
>> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
>> For additional commands, e-mail: users-help@wicket.apache.org
>>
>>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
> For additional commands, e-mail: users-help@wicket.apache.org
>
--
Dr. Jürgen Lind
iteratec GmbH Fon: +49 (0)89 614551-44
Inselkammerstrasse 4 Fax: +49 (0)89 614551-10
82008 Unterhaching Web: www.iteratec.de
Sitz und Registergericht der iteratec GmbH: München HRB 113 519
Geschäftsführer: Klaus Eberhardt, Mark Goerke, Inge Hanschke, Ralf Menzel
---------------------------------------------------------------------
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Re: Problem understanding LoadableDetachableModel and ListViews
Posted by Igor Vaynberg <ig...@gmail.com>.
final TestItem itemModel = (TestItem) item.getModelObject();
^ on this line you retrieve the object from the model, you then use
this reference inside the onclick() which is called during another
request. since you use the model object reference directly it is not
loaded from the model.
my code, on the other hand, never keeps a direct reference to the
model object, instead it retrieves it from the model inside onclick()
-igor
On Thu, Oct 2, 2008 at 10:10 AM, Jürgen Lind <Ju...@iteratec.de> wrote:
> Igor Vaynberg wrote:
>>
>> your link works on the object and not on the model, instead
>>
>> add(new link("delete", item.getmodel()) { onclick() {
>> delete(getmodelobject()); }});
>>
>
> Thank you for your quick reply.
>
> Well the code is roughly the same(?) as in Listing 5.12 of WiA and there
> a custom Model is used to illustrate the solution. However, I thought my
> test would show me the problem first... Using your code above, the
> effect is as expected, i.e. the "wrong" (new) item is returned to be
> deleted.
>
> Now, the question is, what is wrong with my first implementation?
> It would seem that the problem that is solved using a custom ItemModel
> does not even occur. Or does that code prevent wicket from effectively
> detaching model objects and should thus be avoided? What would be the
> best practice here?
>
>
> J.
>
>> -igor
>>
>> On Thu, Oct 2, 2008 at 9:04 AM, Jürgen Lind <Ju...@iteratec.de>
>> wrote:
>>>
>>> Hi there,
>>>
>>> I have been struggling for some time now to understand how
>>> LoadableDetachableModel and a ListView work together. The starting point
>>> was Chapter 5.5.2 of "Wicket in Action" where it is recommended to
>>> provide
>>> your own ItemModel if the underlying list changes frequently. To try out
>>> how Wicket behaves without such a custom ItemModel, I wrote the following
>>> Test:
>>>
>>> <body>
>>> <em wicket:id="listview">
>>> <span wicket:id="label"></span><a wicket:id="delete">delete</a>
>>> </em>
>>> </body>
>>>
>>>
>>> LoadableDetachableModel model = new LoadableDetachableModel() {
>>>
>>> @Override
>>> protected Object load() {
>>> System.out.println("load");
>>> return Arrays.asList(new TestItem[] {
>>> new TestItem("a" + Math.random()),
>>> new TestItem("b" + Math.random()),
>>> new TestItem("c" + Math.random()) });
>>> }
>>>
>>> protected void onDetach() {
>>> System.out.println("detach");
>>> }
>>>
>>> };
>>>
>>> ListView listview = new ListView("listview", model) {
>>> protected void populateItem(ListItem item) {
>>> final TestItem itemModel = (TestItem) item.getModelObject();
>>> item.add(new Label("label", itemModel.toString()));
>>> item.add(new Link("delete") {
>>>
>>> @Override
>>> public void onClick() {
>>> System.out.println("Delete " + itemModel);
>>> }
>>> });
>>> }
>>> };
>>>
>>> add(listview);
>>>
>>>
>>> Now, I would expect that when I hit the "delete" link, Wicket would call
>>> the
>>> "load" Method of the LoadableDetachableModel before printing "Delete..."
>>> as
>>> the
>>> default implementation will use the index and the list to determine the
>>> item
>>> to
>>> delete. To my surprise, however, the "Delete..." message is printed with
>>> the
>>> correct item and the "load" Method is called afterwards. In my
>>> understanding,
>>> this contradicts the idea of the LoadableDetachableModel since Wicket
>>> seems
>>> to
>>> have a copy of the original list somewhere so that it can determine the
>>> list
>>> item on which the action was invoked before loading the underlying list.
>>>
>>> Can someone spot my mistake?
>>>
>>> Thanks,
>>>
>>> J.
>>>
>>> --
>>> Dr. Jürgen Lind
>>> iteratec GmbH Fon: +49 (0)89 614551-44
>>> Inselkammerstrasse 4 Fax: +49 (0)89 614551-10
>>> 82008 Unterhaching Web: www.iteratec.de
>>>
>>> Sitz und Registergericht der iteratec GmbH: München HRB 113 519
>>> Geschäftsführer: Klaus Eberhardt, Mark Goerke, Inge Hanschke, Ralf Menzel
>>>
>>>
>>> ---------------------------------------------------------------------
>>> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
>>> For additional commands, e-mail: users-help@wicket.apache.org
>>>
>>>
>>
>> ---------------------------------------------------------------------
>> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
>> For additional commands, e-mail: users-help@wicket.apache.org
>>
>
> --
> Dr. Jürgen Lind
> iteratec GmbH Fon: +49 (0)89 614551-44
> Inselkammerstrasse 4 Fax: +49 (0)89 614551-10
> 82008 Unterhaching Web: www.iteratec.de
>
> Sitz und Registergericht der iteratec GmbH: München HRB 113 519
> Geschäftsführer: Klaus Eberhardt, Mark Goerke, Inge Hanschke, Ralf Menzel
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
> For additional commands, e-mail: users-help@wicket.apache.org
>
>
---------------------------------------------------------------------
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Re: Problem understanding LoadableDetachableModel and ListViews
Posted by Jürgen Lind <Ju...@iteratec.de>.
Igor Vaynberg wrote:
> your link works on the object and not on the model, instead
>
> add(new link("delete", item.getmodel()) { onclick() {
> delete(getmodelobject()); }});
>
Thank you for your quick reply.
Well the code is roughly the same(?) as in Listing 5.12 of WiA and there
a custom Model is used to illustrate the solution. However, I thought my
test would show me the problem first... Using your code above, the
effect is as expected, i.e. the "wrong" (new) item is returned to be
deleted.
Now, the question is, what is wrong with my first implementation?
It would seem that the problem that is solved using a custom ItemModel
does not even occur. Or does that code prevent wicket from effectively
detaching model objects and should thus be avoided? What would be the
best practice here?
J.
> -igor
>
> On Thu, Oct 2, 2008 at 9:04 AM, Jürgen Lind <Ju...@iteratec.de> wrote:
>> Hi there,
>>
>> I have been struggling for some time now to understand how
>> LoadableDetachableModel and a ListView work together. The starting point
>> was Chapter 5.5.2 of "Wicket in Action" where it is recommended to provide
>> your own ItemModel if the underlying list changes frequently. To try out
>> how Wicket behaves without such a custom ItemModel, I wrote the following
>> Test:
>>
>> <body>
>> <em wicket:id="listview">
>> <span wicket:id="label"></span><a wicket:id="delete">delete</a>
>> </em>
>> </body>
>>
>>
>> LoadableDetachableModel model = new LoadableDetachableModel() {
>>
>> @Override
>> protected Object load() {
>> System.out.println("load");
>> return Arrays.asList(new TestItem[] {
>> new TestItem("a" + Math.random()),
>> new TestItem("b" + Math.random()),
>> new TestItem("c" + Math.random()) });
>> }
>>
>> protected void onDetach() {
>> System.out.println("detach");
>> }
>>
>> };
>>
>> ListView listview = new ListView("listview", model) {
>> protected void populateItem(ListItem item) {
>> final TestItem itemModel = (TestItem) item.getModelObject();
>> item.add(new Label("label", itemModel.toString()));
>> item.add(new Link("delete") {
>>
>> @Override
>> public void onClick() {
>> System.out.println("Delete " + itemModel);
>> }
>> });
>> }
>> };
>>
>> add(listview);
>>
>>
>> Now, I would expect that when I hit the "delete" link, Wicket would call the
>> "load" Method of the LoadableDetachableModel before printing "Delete..." as
>> the
>> default implementation will use the index and the list to determine the item
>> to
>> delete. To my surprise, however, the "Delete..." message is printed with the
>> correct item and the "load" Method is called afterwards. In my
>> understanding,
>> this contradicts the idea of the LoadableDetachableModel since Wicket seems
>> to
>> have a copy of the original list somewhere so that it can determine the list
>> item on which the action was invoked before loading the underlying list.
>>
>> Can someone spot my mistake?
>>
>> Thanks,
>>
>> J.
>>
>> --
>> Dr. Jürgen Lind
>> iteratec GmbH Fon: +49 (0)89 614551-44
>> Inselkammerstrasse 4 Fax: +49 (0)89 614551-10
>> 82008 Unterhaching Web: www.iteratec.de
>>
>> Sitz und Registergericht der iteratec GmbH: München HRB 113 519
>> Geschäftsführer: Klaus Eberhardt, Mark Goerke, Inge Hanschke, Ralf Menzel
>>
>>
>> ---------------------------------------------------------------------
>> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
>> For additional commands, e-mail: users-help@wicket.apache.org
>>
>>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
> For additional commands, e-mail: users-help@wicket.apache.org
>
--
Dr. Jürgen Lind
iteratec GmbH Fon: +49 (0)89 614551-44
Inselkammerstrasse 4 Fax: +49 (0)89 614551-10
82008 Unterhaching Web: www.iteratec.de
Sitz und Registergericht der iteratec GmbH: München HRB 113 519
Geschäftsführer: Klaus Eberhardt, Mark Goerke, Inge Hanschke, Ralf Menzel
---------------------------------------------------------------------
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Re: Problem understanding LoadableDetachableModel and ListViews
Posted by Igor Vaynberg <ig...@gmail.com>.
your link works on the object and not on the model, instead
add(new link("delete", item.getmodel()) { onclick() {
delete(getmodelobject()); }});
-igor
On Thu, Oct 2, 2008 at 9:04 AM, Jürgen Lind <Ju...@iteratec.de> wrote:
> Hi there,
>
> I have been struggling for some time now to understand how
> LoadableDetachableModel and a ListView work together. The starting point
> was Chapter 5.5.2 of "Wicket in Action" where it is recommended to provide
> your own ItemModel if the underlying list changes frequently. To try out
> how Wicket behaves without such a custom ItemModel, I wrote the following
> Test:
>
> <body>
> <em wicket:id="listview">
> <span wicket:id="label"></span><a wicket:id="delete">delete</a>
> </em>
> </body>
>
>
> LoadableDetachableModel model = new LoadableDetachableModel() {
>
> @Override
> protected Object load() {
> System.out.println("load");
> return Arrays.asList(new TestItem[] {
> new TestItem("a" + Math.random()),
> new TestItem("b" + Math.random()),
> new TestItem("c" + Math.random()) });
> }
>
> protected void onDetach() {
> System.out.println("detach");
> }
>
> };
>
> ListView listview = new ListView("listview", model) {
> protected void populateItem(ListItem item) {
> final TestItem itemModel = (TestItem) item.getModelObject();
> item.add(new Label("label", itemModel.toString()));
> item.add(new Link("delete") {
>
> @Override
> public void onClick() {
> System.out.println("Delete " + itemModel);
> }
> });
> }
> };
>
> add(listview);
>
>
> Now, I would expect that when I hit the "delete" link, Wicket would call the
> "load" Method of the LoadableDetachableModel before printing "Delete..." as
> the
> default implementation will use the index and the list to determine the item
> to
> delete. To my surprise, however, the "Delete..." message is printed with the
> correct item and the "load" Method is called afterwards. In my
> understanding,
> this contradicts the idea of the LoadableDetachableModel since Wicket seems
> to
> have a copy of the original list somewhere so that it can determine the list
> item on which the action was invoked before loading the underlying list.
>
> Can someone spot my mistake?
>
> Thanks,
>
> J.
>
> --
> Dr. Jürgen Lind
> iteratec GmbH Fon: +49 (0)89 614551-44
> Inselkammerstrasse 4 Fax: +49 (0)89 614551-10
> 82008 Unterhaching Web: www.iteratec.de
>
> Sitz und Registergericht der iteratec GmbH: München HRB 113 519
> Geschäftsführer: Klaus Eberhardt, Mark Goerke, Inge Hanschke, Ralf Menzel
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
> For additional commands, e-mail: users-help@wicket.apache.org
>
>
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