You are viewing a plain text version of this content. The canonical link for it is here.
Posted to users@wicket.apache.org by marcus dickerhof <ma...@googlemail.com> on 2007/10/12 14:00:56 UTC
Anonymous or nested instances of IModel?
Hi,
I am quite new to wicket, and I want to avoid making serious mistakes :-)
On the Bestpractices and gotachs page:
http://cwiki.apache.org/WICKET/best-practices-and-gotchas.html
I found the following statement from Martijn Dashorst:
--START
The other thing to avoid is anonymous or nested instances of IModel. Usually
you share an instance of a model between two page instances. If you create
an anonymous or nested instance of IModel, then you automatically get a
'this' reference to the class that surrounds it. This will usually be the
page, but can also be the form or a listview. Anyway, because the reference
is /final/, you will copy that reference to the old page, with the model to
the new page, thus duplicating the component tree (it gets versioned etc.).
This will eventually lead to OutOfMemoryError.
Search in the mailinglist for outofmemoryerror for other descriptions of
this behaviour. I doubt that I have done the subject justice.
--END
Is this still an issue? And how would I do a
workaround? Where can I find more infos concerning this problem?
Thanks a lot!
Best regards
Marcus
Re: Anonymous or nested instances of IModel?
Posted by Igor Vaynberg <ig...@gmail.com>.
yes, because you do not pass it between pages.
the problem really is that an anonymous class dangles a reference to the
parent. so if you pass an anon model created in page A to page B that model
still has a reference to page A so your session is a bit bigger because page
B always has a reference to page A.
-igor
On 10/12/07, marcus dickerhof <ma...@googlemail.com> wrote:
>
> Hi,
> here comes my example:
>
> class MyWizard extends Wizard{
>
> private String tempfile;
>
> ...
>
> private final class Step1 extends WizardStep {
> //uploads file to some temp-folder + sets the tempfile name
> }
>
> private final class Step2 extends WizardStep {
> //Shows a summary Page + confirm button +
> //a link to delete the temp file that was uploaded in Step1
> public Step2(){
> ......
> --> is the following line ok???
> add(new Label("file", new PropertyModel(MyWizard.this, "tempfile" )
> )
> );
> add(new Link("delete")
> {
>
> public void onClick()
> {
>
> final File file = new File( MyWizard.this.tempfile );
> Files.remove(file);
> MyWizard.this.info("Deleted " + file);
>
> }
>
> });
>
>
>
> }
>
> }
>
>
> }
>
> Thanks!
> -Marcus
>
>
>
> 2007/10/12, Igor Vaynberg <ig...@gmail.com>:
> >
> > it is still an issue if you pass such a model between pages. i dont see
> > why
> > you would need an anonymous model instance.
> >
> > -igor
> >
> >
> > On 10/12/07, marcus dickerhof <ma...@googlemail.com> wrote:
> > >
> > > Hi,
> > > I am quite new to wicket, and I want to avoid making serious mistakes
> > :-)
> > > On the Bestpractices and gotachs page:
> > > http://cwiki.apache.org/WICKET/best-practices-and-gotchas.html
> > > I found the following statement from Martijn Dashorst:
> > >
> > > --START
> > > The other thing to avoid is anonymous or nested instances of IModel.
> > > Usually
> > > you share an instance of a model between two page instances. If you
> > create
> > > an anonymous or nested instance of IModel, then you automatically get
> a
> > > 'this' reference to the class that surrounds it. This will usually be
> > the
> > > page, but can also be the form or a listview. Anyway, because the
> > > reference
> > > is /final/, you will copy that reference to the old page, with the
> model
> > > to
> > > the new page, thus duplicating the component tree (it gets versioned
> > > etc.).
> > > This will eventually lead to OutOfMemoryError.
> > >
> > > Search in the mailinglist for outofmemoryerror for other descriptions
> of
> > > this behaviour. I doubt that I have done the subject justice.
> > >
> > > --END
> > >
> > > Is this still an issue? And how would I do a
> > > workaround? Where can I find more infos concerning this problem?
> > >
> > >
> > > Thanks a lot!
> > >
> > > Best regards
> > > Marcus
> > >
> >
>
Re: Anonymous or nested instances of IModel?
Posted by marcus dickerhof <ma...@googlemail.com>.
Hi,
here comes my example:
class MyWizard extends Wizard{
private String tempfile;
...
private final class Step1 extends WizardStep {
//uploads file to some temp-folder + sets the tempfile name
}
private final class Step2 extends WizardStep {
//Shows a summary Page + confirm button +
//a link to delete the temp file that was uploaded in Step1
public Step2(){
......
--> is the following line ok???
add(new Label("file", new PropertyModel(MyWizard.this, "tempfile" ) )
);
add(new Link("delete")
{
public void onClick()
{
final File file = new File( MyWizard.this.tempfile );
Files.remove(file);
MyWizard.this.info("Deleted " + file);
}
});
}
}
}
Thanks!
-Marcus
2007/10/12, Igor Vaynberg <ig...@gmail.com>:
>
> it is still an issue if you pass such a model between pages. i dont see
> why
> you would need an anonymous model instance.
>
> -igor
>
>
> On 10/12/07, marcus dickerhof <ma...@googlemail.com> wrote:
> >
> > Hi,
> > I am quite new to wicket, and I want to avoid making serious mistakes
> :-)
> > On the Bestpractices and gotachs page:
> > http://cwiki.apache.org/WICKET/best-practices-and-gotchas.html
> > I found the following statement from Martijn Dashorst:
> >
> > --START
> > The other thing to avoid is anonymous or nested instances of IModel.
> > Usually
> > you share an instance of a model between two page instances. If you
> create
> > an anonymous or nested instance of IModel, then you automatically get a
> > 'this' reference to the class that surrounds it. This will usually be
> the
> > page, but can also be the form or a listview. Anyway, because the
> > reference
> > is /final/, you will copy that reference to the old page, with the model
> > to
> > the new page, thus duplicating the component tree (it gets versioned
> > etc.).
> > This will eventually lead to OutOfMemoryError.
> >
> > Search in the mailinglist for outofmemoryerror for other descriptions of
> > this behaviour. I doubt that I have done the subject justice.
> >
> > --END
> >
> > Is this still an issue? And how would I do a
> > workaround? Where can I find more infos concerning this problem?
> >
> >
> > Thanks a lot!
> >
> > Best regards
> > Marcus
> >
>
Re: Anonymous or nested instances of IModel?
Posted by Igor Vaynberg <ig...@gmail.com>.
it is still an issue if you pass such a model between pages. i dont see why
you would need an anonymous model instance.
-igor
On 10/12/07, marcus dickerhof <ma...@googlemail.com> wrote:
>
> Hi,
> I am quite new to wicket, and I want to avoid making serious mistakes :-)
> On the Bestpractices and gotachs page:
> http://cwiki.apache.org/WICKET/best-practices-and-gotchas.html
> I found the following statement from Martijn Dashorst:
>
> --START
> The other thing to avoid is anonymous or nested instances of IModel.
> Usually
> you share an instance of a model between two page instances. If you create
> an anonymous or nested instance of IModel, then you automatically get a
> 'this' reference to the class that surrounds it. This will usually be the
> page, but can also be the form or a listview. Anyway, because the
> reference
> is /final/, you will copy that reference to the old page, with the model
> to
> the new page, thus duplicating the component tree (it gets versioned
> etc.).
> This will eventually lead to OutOfMemoryError.
>
> Search in the mailinglist for outofmemoryerror for other descriptions of
> this behaviour. I doubt that I have done the subject justice.
>
> --END
>
> Is this still an issue? And how would I do a
> workaround? Where can I find more infos concerning this problem?
>
>
> Thanks a lot!
>
> Best regards
> Marcus
>