That's actually also an example of why I prefer overriding isVisible:
I can have that button and other widgets (maybe completely unrelated)
widgets that depend on a particular state (like whether a record
exists), and a function (override of isVisible) will always yield the
correct result. In contrast, relying on the internal component state
(set/isVisible) puts the responsibility of updating the relevant
components on the handler (or worse, it may have to be triggered from
the business layer).
Eelco
On Fri, Dec 3, 2010 at 10:46 AM, Igor Vaynberg <igor.vaynb...@gmail.com> wrote:
> ldm also doesnt always work nicely. suppose you have a delete button
> that is only visible if the record exists. the page renders, the user
> clicks the button. the onclick handler invoked, and isvisible is
> checked - at which point it is true. the record is deleted in the
> onclick handler, the page is rerendered - delete button is still
> visible because the ldm has cached the visibility value from before
> onclick handler is invoked. to make it work correctly the ldm would
> have to be detached manually after onclick handler.
>
> -igor
>
> On Thu, Dec 2, 2010 at 6:36 PM, Clint Checketts <checke...@gmail.com> wrote:
>> Yesterday a friend following this thread pointed out that we should rethink
>> our overriding of onVisible and use onConfigure. I've used
>> LoadabledDetachableModels to cache the value used in my isVisible/isEnabled
>> overriding so changing values mid request aren't a problem. That is its
>> whole purpose. Also calling .detach() on that model isn't hacky, that is its
>> design.
>>
>> While I appreciate having onConfigure as an option it seems like overriding
>> isVisible is still the cleaner and clearer way. Folks just need to follow
>> the rule that expensive calls should be contained in an LDM.
>>
>> Am I stuck in the past in holding this view?
>>
>> -Clint
>>
>> On Thu, Dec 2, 2010 at 4:03 AM, Martin Makundi <
>> martin.maku...@koodaripalvelut.com> wrote:
>>
>>> What about using onconfigure to replace loadabledetachablemodel ? We
>>> have had some trouble with loadabledetachablemodels when their state
>>> is frozen before a dependent model has been initialized (for example)
>>> and we need to call model.detach() from within our code, which seems
>>> bit hacky.
>>>
>>> Initializing also models at a specific known requestcycle moment might
>>> be beneficial. Ofcourse it is not so straightforward as with
>>> enable/visible state.
>>>
>>> **
>>> Martin
>>>
>>> 2010/12/1 Igor Vaynberg <igor.vaynb...@gmail.com>:
>>> > i would be happy if that was good enough. in the past it hasnt been,
>>> > thats why we have the current solution. maybe we can try it again in
>>> > 1.5 and see what happens.
>>> >
>>> > -igor
>>> >
>>> > On Tue, Nov 30, 2010 at 11:44 AM, Pedro Santos <pedros...@gmail.com>
>>> wrote:
>>> >> I have a different point of view, the HTTP imposes us some limitations,
>>> we
>>> >> will hardly have an good synchronization between the component state on
>>> >> browser and server using only HTTP conversation. So it is mandatory the
>>> >> service layer to respect the described security restriction.
>>> >>
>>> >> On Tue, Nov 30, 2010 at 5:32 PM, Igor Vaynberg <igor.vaynb...@gmail.com
>>> >wrote:
>>> >>
>>> >>> an easy example is security.
>>> >>>
>>> >>> a user views a page that allows them to delete another user
>>> >>> meanwhile their permissions are tweaked and they can no longer delete
>>> >>> other users
>>> >>> half an hour later the user clicks the delete button - this should
>>> >>> fail, but wont if we are using last-rendered state.
>>> >>>
>>> >>> -igor
>>> >>>
>>> >>> On Tue, Nov 30, 2010 at 11:18 AM, Pedro Santos <pedros...@gmail.com>
>>> >>> wrote:
>>> >>> > I need to look better on which core components are relying on an
>>> updated
>>> >>> > visibility/enabled state at the process event time, and why the last
>>> >>> > rendered state wouldn't be enough to them to work nicely.
>>> >>> >
>>> >>> > On Tue, Nov 30, 2010 at 3:19 PM, Igor Vaynberg <
>>> igor.vaynb...@gmail.com
>>> >>> >wrote:
>>> >>> >
>>> >>> >> currently we only invoke configure before the render. this would
>>> mean
>>> >>> >> we would have to invoke it before processing a listener, clearing
>>> the
>>> >>> >> cache, and then invoking it again before render. i wonder if that is
>>> >>> >> enough places to invoke it....
>>> >>> >>
>>> >>> >> -igor
>>> >>> >>
>>> >>> >> On Tue, Nov 30, 2010 at 9:15 AM, Pedro Santos <pedros...@gmail.com>
>>> >>> wrote:
>>> >>> >> > If user click an link, it will change the value of some property
>>> at
>>> >>> the
>>> >>> >> > process_event request cycle step. Then the processor will go to
>>> the
>>> >>> >> respond
>>> >>> >> > step, will invoke every component before render method which will
>>> end
>>> >>> up
>>> >>> >> > invoking the Component#configure and updating the
>>> visibility/enabled
>>> >>> >> state
>>> >>> >> > (even if it changes, we are able to work with the updated state).
>>> So
>>> >>> when
>>> >>> >> > the this component has the opportunity to render it self, it will
>>> be
>>> >>> >> aware
>>> >>> >> > its update state.
>>> >>> >> >
>>> >>> >> > On Tue, Nov 30, 2010 at 2:39 PM, Igor Vaynberg <
>>> >>> igor.vaynb...@gmail.com
>>> >>> >> >wrote:
>>> >>> >> >
>>> >>> >> >> there are other places that should be checked though. for example
>>> >>> >> >> before we invoke a listener on the component we should check
>>> again to
>>> >>> >> >> make sure that visibility hasnt changed. eg if visibility depends
>>> on
>>> >>> >> >> some property of the user clicking the link that changed between
>>> >>> >> >> render and clicking the link.
>>> >>> >> >>
>>> >>> >> >> -igor
>>> >>> >> >>
>>> >>> >> >> On Tue, Nov 30, 2010 at 8:30 AM, Pedro Santos <
>>> pedros...@gmail.com>
>>> >>> >> wrote:
>>> >>> >> >> > An implementation idea:
>>> >>> >> >> >
>>> >>> >> >> > Component {
>>> >>> >> >> > public final void configure()
>>> >>> >> >> > {
>>> >>> >> >> > if (!getFlag(FLAG_CONFIGURED))
>>> >>> >> >> > {
>>> >>> >> >> > setVisible_NoClientCode(isVisible()); //we only
>>> check
>>> >>> the
>>> >>> >> user
>>> >>> >> >> > isVisible in here
>>> >>> >> >> > onConfigure();
>>> >>> >> >> > setFlag(FLAG_CONFIGURED, true);
>>> >>> >> >> > }
>>> >>> >> >> > }
>>> >>> >> >> > }
>>> >>> >> >> >
>>> >>> >> >> > On Tue, Nov 30, 2010 at 2:16 PM, Igor Vaynberg <
>>> >>> >> igor.vaynb...@gmail.com
>>> >>> >> >> >wrote:
>>> >>> >> >> >
>>> >>> >> >> >> so how is it different if they can still override something
>>> that
>>> >>> >> needs
>>> >>> >> >> >> to be checked all the time?
>>> >>> >> >> >>
>>> >>> >> >> >> -igor
>>> >>> >> >> >>
>>> >>> >> >> >> On Tue, Nov 30, 2010 at 8:02 AM, Pedro Santos <
>>> >>> pedros...@gmail.com>
>>> >>> >> >> wrote:
>>> >>> >> >> >> > I understand the concern about possible isVisible
>>> >>> implementations
>>> >>> >> like
>>> >>> >> >> >> >
>>> >>> >> >> >> > isVisible(return currentlyTime < 10:00:00;) //imagine this
>>> >>> >> component
>>> >>> >> >> >> being
>>> >>> >> >> >> > rendered at 09:59:59
>>> >>> >> >> >> > isVisible(return dao.list().size() > 0);// performance
>>> issues
>>> >>> >> >> >> >
>>> >>> >> >> >> > But maybe we can have the best from both approaches. This is
>>> an
>>> >>> >> >> >> copy/paste
>>> >>> >> >> >> > from java.awt.Component:
>>> >>> >> >> >> >
>>> >>> >> >> >> > public boolean isVisible() {
>>> >>> >> >> >> > return isVisible_NoClientCode();
>>> >>> >> >> >> > }
>>> >>> >> >> >> > final boolean isVisible_NoClientCode() {
>>> >>> >> >> >> > return visible;
>>> >>> >> >> >> > }
>>> >>> >> >> >> >
>>> >>> >> >> >> > There are some points in the awt framework were the
>>> isVisible
>>> >>> >> method
>>> >>> >> >> is
>>> >>> >> >> >> not
>>> >>> >> >> >> > used in benefit of isVisible_NoClientCode
>>> >>> >> >> >> > I'm in favor of create an final isVisible/Enabled version
>>> and
>>> >>> >> change
>>> >>> >> >> the
>>> >>> >> >> >> > Wicket core to use it. Also maintain the hotspot to users
>>> >>> provide
>>> >>> >> >> their
>>> >>> >> >> >> > isVisible/Enable implementations that will serve to feed the
>>> >>> core
>>> >>> >> >> >> component
>>> >>> >> >> >> > state.
>>> >>> >> >> >> >
>>> >>> >> >> >> > On Mon, Nov 29, 2010 at 4:56 PM, Igor Vaynberg <
>>> >>> >> >> igor.vaynb...@gmail.com
>>> >>> >> >> >> >wrote:
>>> >>> >> >> >> >
>>> >>> >> >> >> >> ive run into plenty of weird problems with overrides, but
>>> maybe
>>> >>> >> >> >> >> because this was in a high concurrency app where data
>>> changed
>>> >>> >> >> >> >> frequently. the problems arise from the fact that the value
>>> >>> >> returned
>>> >>> >> >> >> >> from isvisible() can change while we are doing traversals,
>>> etc.
>>> >>> >> >> >> >>
>>> >>> >> >> >> >> eg we run a traversal for all visible components and put
>>> them
>>> >>> in a
>>> >>> >> >> >> >> list. later we iterate over the list and try to render
>>> these
>>> >>> >> >> >> >> components. the render function also checks their
>>> visibility
>>> >>> and
>>> >>> >> if
>>> >>> >> >> >> >> they are no longer visible it throws an exception.
>>> >>> >> >> >> >>
>>> >>> >> >> >> >> if isvisible() override depends on some external factor
>>> like
>>> >>> the
>>> >>> >> >> >> >> database there is a small window where the value can change
>>> and
>>> >>> >> now
>>> >>> >> >> >> >> you can have a weird exception: such as "tried to invoke a
>>> >>> >> listener
>>> >>> >> >> on
>>> >>> >> >> >> >> a component that is not visible or not enabled". these are
>>> very
>>> >>> >> >> >> >> intermittent and damn near impossible to reproduce.
>>> >>> >> >> >> >>
>>> >>> >> >> >> >> another problem is performance. isvisible() is called
>>> multiple
>>> >>> >> times
>>> >>> >> >> >> >> during the request and if it depends on the database it can
>>> be
>>> >>> a
>>> >>> >> >> >> >> performance problem. in fact a couple of users have
>>> complained
>>> >>> >> about
>>> >>> >> >> >> >> this on the list in the past. at least now we have an easy
>>> >>> >> solution
>>> >>> >> >> >> >> for them - use onconfigure().
>>> >>> >> >> >> >>
>>> >>> >> >> >> >> so as of right now the developers have two choices:
>>> override
>>> >>> >> >> >> >> isvisible() and potentially suffer the consequences. or,
>>> >>> override
>>> >>> >> >> >> >> onconfigure() and set visibility there in a more
>>> deterministic
>>> >>> >> >> >> >> fashion.
>>> >>> >> >> >> >>
>>> >>> >> >> >> >> -igor
>>> >>> >> >> >> >>
>>> >>> >> >> >> >>
>>> >>> >> >> >> >>
>>> >>> >> >> >> >> On Mon, Nov 29, 2010 at 10:21 AM, Eelco Hillenius
>>> >>> >> >> >> >> <eelco.hillen...@gmail.com> wrote:
>>> >>> >> >> >> >> > To expand, unless I'm missing something (new?), things
>>> are
>>> >>> >> really
>>> >>> >> >> only
>>> >>> >> >> >> >> > problematic when both the mutable value and the override
>>> are
>>> >>> >> mixed.
>>> >>> >> >> In
>>> >>> >> >> >> >> > a way, I think that using the override is 'more pure', as
>>> >>> it's a
>>> >>> >> >> >> >> > simple function that is executed when needed, whereas
>>> mutable
>>> >>> >> state
>>> >>> >> >> >> >> > can be harder to deal with when trying to figure out how
>>> it
>>> >>> got
>>> >>> >> to
>>> >>> >> >> be
>>> >>> >> >> >> >> > in that state. So, sorry Igor, but we disagree on this
>>> one.
>>> >>> >> >> >> >> >
>>> >>> >> >> >> >> > Eelco
>>> >>> >> >> >> >> >
>>> >>> >> >> >> >> >
>>> >>> >> >> >> >> > On Mon, Nov 29, 2010 at 10:13 AM, Eelco Hillenius
>>> >>> >> >> >> >> > <eelco.hillen...@gmail.com> wrote:
>>> >>> >> >> >> >> >> Niether is evil. It has potential pitfalls, which you
>>> should
>>> >>> >> just
>>> >>> >> >> be
>>> >>> >> >> >> >> >> aware of. We use such overrides all over the place and
>>> never
>>> >>> >> have
>>> >>> >> >> >> >> >> problems with them either. :-) Avoiding it is safer, but
>>> >>> also
>>> >>> >> more
>>> >>> >> >> >> >> >> verbose (in 1.3.x at least).
>>> >>> >> >> >> >> >>
>>> >>> >> >> >> >> >> Eelco
>>> >>> >> >> >> >> >>
>>> >>> >> >> >> >> >> On Mon, Nov 29, 2010 at 9:49 AM, Igor Vaynberg <
>>> >>> >> >> >> igor.vaynb...@gmail.com>
>>> >>> >> >> >> >> wrote:
>>> >>> >> >> >> >> >>> On Mon, Nov 29, 2010 at 9:35 AM, Sven Meier <
>>> >>> s...@meiers.net>
>>> >>> >> >> >> wrote:
>>> >>> >> >> >> >> >>>> Hi Douglas,
>>> >>> >> >> >> >> >>>>
>>> >>> >> >> >> >> >>>> WICKET-3171 describes a problematic case, where
>>> visibility
>>> >>> of
>>> >>> >> a
>>> >>> >> >> >> >> >>>> component changes while its form is being processed.
>>> >>> >> >> >> >> >>>> In our projects we're overriding isVisible() where
>>> >>> >> appropriate
>>> >>> >> >> and
>>> >>> >> >> >> >> never
>>> >>> >> >> >> >> >>>> encountered a similar problem.
>>> >>> >> >> >> >> >>>>
>>> >>> >> >> >> >> >>>> I'd say WICKET-3171 is the rare 5% usecase. What's
>>> next,
>>> >>> is
>>> >>> >> >> >> overriding
>>> >>> >> >> >> >> >>>> isEnabled() going to be declared evil too? ;)
>>> >>> >> >> >> >> >>>
>>> >>> >> >> >> >> >>> yes
>>> >>> >> >> >> >> >>>
>>> >>> >> >> >> >> >>> -igor
>>> >>> >> >> >> >> >>>
>>> >>> >> >> >> >> >>>>
>>> >>> >> >> >> >> >>>> Sven
>>> >>> >> >> >> >> >>>>
>>> >>> >> >> >> >> >>>> On Mon, 2010-11-29 at 11:22 -0600, Douglas Ferguson
>>> wrote:
>>> >>> >> >> >> >> >>>>
>>> >>> >> >> >> >> >>>>> Can you explain why? We have done this all over the
>>> >>> place.
>>> >>> >> >> >> >> >>>>>
>>> >>> >> >> >> >> >>>>> D/
>>> >>> >> >> >> >> >>>>>
>>> >>> >> >> >> >> >>>>> On Nov 29, 2010, at 10:00 AM, Martin Grigorov wrote:
>>> >>> >> >> >> >> >>>>>
>>> >>> >> >> >> >> >>>>> > The recommended way since a few 1.4 releases is to
>>> >>> >> override
>>> >>> >> >> >> >> onConfigure()
>>> >>> >> >> >> >> >>>>> > and call setVisible(true|false) depending on your
>>> >>> >> conditions.
>>> >>> >> >> >> >> >>>>> >
>>> >>> >> >> >> >> >>>>> > On Mon, Nov 29, 2010 at 4:49 PM, Douglas Ferguson <
>>> >>> >> >> >> >> >>>>> > doug...@douglasferguson.us> wrote:
>>> >>> >> >> >> >> >>>>> >
>>> >>> >> >> >> >> >>>>> >> Igor posted a comment to this bug saying that
>>> >>> overriding
>>> >>> >> >> >> >> isVisible() is
>>> >>> >> >> >> >> >>>>> >> "evil"
>>> >>> >> >> >> >> >>>>> >>
>>> >>> >> >> >> >> >>>>> >>
>>> >>> https://issues.apache.org/jira/browse/WICKET-3171
>>> >>> >> >> >> >> >>>>> >>
>>> >>> >> >> >> >> >>>>> >> I was surprised by this and am curious to hear
>>> more.
>>> >>> >> >> >> >> >>>>> >>
>>> >>> >> >> >> >> >>>>> >> D/
>>> >>> >> >> >> >> >>>>>
>>> >>> >> >> >> >> >>>>
>>> >>> >> >> >> >> >>>>
>>> >>> >> >> >> >> >>>>
>>> >>> >> >> >> >> >>>
>>> >>> >> >> >> >> >>
>>> >>> >> >> >> >> >
>>> >>> >> >> >> >>
>>> >>> >> >> >> >
>>> >>> >> >> >> >
>>> >>> >> >> >> >
>>> >>> >> >> >> > --
>>> >>> >> >> >> > Pedro Henrique Oliveira dos Santos
>>> >>> >> >> >> >
>>> >>> >> >> >>
>>> >>> >> >> >
>>> >>> >> >> >
>>> >>> >> >> >
>>> >>> >> >> > --
>>> >>> >> >> > Pedro Henrique Oliveira dos Santos
>>> >>> >> >> >
>>> >>> >> >>
>>> >>> >> >
>>> >>> >> >
>>> >>> >> >
>>> >>> >> > --
>>> >>> >> > Pedro Henrique Oliveira dos Santos
>>> >>> >> >
>>> >>> >>
>>> >>> >
>>> >>> >
>>> >>> >
>>> >>> > --
>>> >>> > Pedro Henrique Oliveira dos Santos
>>> >>> >
>>> >>>
>>> >>
>>> >>
>>> >>
>>> >> --
>>> >> Pedro Henrique Oliveira dos Santos
>>> >>
>>> >
>>>
>>
>
