This is why ISortStateLocator also has a setter (just like imodel). It itself is never serialized as part of the change, but the object it points to is. When the change is restored the setter on the locator is called to restore the object.
here is a snippet from the SortStateChange ( it is an internal class so the ref to ISortStateLocator stateLocator comes form the parent class):
private final class SortStateChange extends Change
{
private final ISortState old = (ISortState)Objects.clone( stateLocator.getSortState());
public void undo()
{
stateLocator.setSortState(old);
}
}
The locator is never serialized as part of the change, the change retains a reference to it. It is the underlying state object that is cloned, and when the change is undone it is reset on the locator.
Eventually the ISortStateLocator is serialized when the page is replicated, but then it is only serialized once and all other references link to the same serialized instance, so when it deserializes it does not get duplicated like you suggest.
-Igor
On 12/6/05, Christian Essl <[EMAIL PROTECTED]> wrote:
I think they are wicket-specific, because where outside of wicket would
you need a wicket interface?
And if you implement it yourself you will have to think of versioning,
otherwise you will have to think of versioning everytime you just use it.
For now I'd say have for POJO IFilterLocator a
rememberVersion(IStateRecorder) method (but name it different) Than it is
explicit what is going on and it is easier to use. (The same could be done
for ISortState). (Again IFilterLocator should take a Serializable and
maybe Ojbects.clone() could check if the cloneable implements Cloneable)
Generally I think IModels which need versioning and the underlying object
does not do it itself (which POJOs) should implement an interface and this
should be as:
IPOJOVersionable{
rememberVersion(IStateRecorder recorder);
}
The user than has to call this method on the Model.
I think this is better because:
a) it is more explicit. which ordinary user - like me knows - what is
going on in modelChanging()
b) currently only the model gets cloned which for pojos only has an effect
if you use a model with a non transient reference
c) you can not share the same underlying POJO instance between different
components because after the roleback you will end with two instances
(transparently)
d) I often use more than one POJO ie in a Form so if I need versioning I
want to version them both without the need of an extra component for
registering the Pojo.
Christian
On Tue, 6 Dec 2005 15:36:55 -0800, Igor Vaynberg <[EMAIL PROTECTED]>
wrote:
> I guess the question is do we want to infact make it something
> wicket-specific. right now its just an ordinary pojo you can use anywhere
> you like. but if we roll the versioning logic into it, it really does
> become
> locked to wicket. that is why i struggled to find a way to keep
> versioning
> out of it - it allows users to work with simple pojos.
>
> by keeping it an pojo there is another advantage - it is easier to expand
> on. For example IFilterLocator works with ordinary objects that are used
> as
> a model for the filter form. everytime you write a filter model
> (normally a
> simple bean) do you want to deal with versioning everytime or would you
> rather let the filter toolbar do it for you?
>
> by keeping the versioning out of models we shift the versioning into
> toolbars. most users will use toolbars and not create them so i think its
> better to keep stuff like that out and let the users who create toolbars
> know that they should version the model they are provided if they want
> the
> backbutton to work - but that is not any different then creating any
> other
> custom component that modifies data - so this isnt even anything special
> about toolbars.
>
> -Igor
>
>
>
> On 12/6/05, Christian Essl < [EMAIL PROTECTED]> wrote:
>>
>> On Tue, 6 Dec 2005 12:25:23 -0800, Igor Vaynberg
>> <[EMAIL PROTECTED]>
>> wrote:
>>
>> > So to summarize your idea it would be like this
>> >
>> > class SingleSortState
>> > IChangeRecorder recorder;
>> > SortState(IChangeRecorder) {...}
>> >
>> > setPropertyState(...) {
>> > recorder.addChange( new Change() {...} )
>> > }
>> >
>> > OrderByLink { onclick () { getState().setProperty(...); } }
>> >
>> > this has the same net affect as
>> >
>> > OrderByLink { onclick() { addstatechange(new Change() { ...
>> > clone(getState()); }); getState().setProperty(...); } }
>> >
>>
>> Right.
>>
>> >
>> > Your way shifts a lot more responsibility into the model because it
>> > needs to
>> > know how to version itself, and most models in wicket need to do that
>> to
>> > support the back button. That means you can no longer user your pojo
>> > models
>> > as wicket models. for example i can no longer reuse my Person pojo
>> from
>> > the
>> > domain layer because it has no concept of versioning. am i totally off
>> > here?
>> > Thats the advantage of doing it on component side - your models can
>> stay
>> > dumb pojos and the component takes care of versioning them by using
>> the
>> > only
>> > fool-proof way it can - cloning.
>> >
>> > -Igor
>>
>> You are right I definately went too far. ModelChanging triggers a
>> versioning clone - did not know that. Propably I did not see it because
>> I
>> mainly use my Pojos from the DB and I do not version them. Thanks for
>> the
>> advice I now understand versioning a bit better.
>>
>> But back to the SortState: I think for such Wicket only models it is
>> still
>> more convinient to do it directly inside the model. In the end you will
>> have to 'version' it somehow and while you are right that the only entry
>> is through a component there can be many entry-points. And than it is a
>> good candidate to refactor it in one place - why not the model?
>>
>> Christian
>>
>> --
>> Christian Essl
>>
>>
>>
>>
>>
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