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https://issues.apache.org/jira/browse/WICKET-6987?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Martin Tzvetanov Grigorov resolved WICKET-6987.
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Resolution: Not A Problem
Answered at https://stackoverflow.com/a/72471937/497381
> Panel replace method detach parent model
> ----------------------------------------
>
> Key: WICKET-6987
> URL: https://issues.apache.org/jira/browse/WICKET-6987
> Project: Wicket
> Issue Type: Bug
> Components: wicket
> Affects Versions: 9.10.0
> Reporter: leclerc cyril
> Priority: Major
> Attachments: image-2022-06-02-08-57-50-406.png,
> image-2022-06-02-09-01-25-801.png
>
>
> In a page (extends {*}webPage{*}) when we replace a component in a panel with
> _panel.replace_ or {_}panel.addOrReplace{_}, when it remove the old
> component, the method detach is called and will detach the parent model
> instead of it own model if present. it cause a reload of the model when the
> new composant is added.
> So imagine you have a panel with 20 components using 1 detachablemodel (wit
> some db queries), and on submit or on action we want to add all components
> in panel (loaded by a class), all are using the same model loaded once on the
> first *_getModel_* call , then all components will use same model value, and
> then detach is called => ok
>
> But if we have a button will submit a form, and we create new components and
> replace in our panel, on each replace method, the remove method will detach
> parent model, so then on each component it will load the model (so 20x load
> model called)
>
> How to reproduce ?
> take a helloworld projet, create a panel with one component Label using a
> detachable string model
> in HomePage constructor set panel, then first add the component, then replace
> it then make something else (getObject for example), on replace method model
> in page will be detached and we have to reload it
>
> {code:java}
> public class HomePage extends WebPage {
> private static final long serialVersionUID = 1L;
> Panel panel ;
> IModel<String> model = new LoadableDetachableModel<String>() {
> @Override
> protected String load() {
> return "test";
> }
> @Override
> protected void onDetach() {
> super.onDetach();
> }
> };
> public HomePage(final PageParameters parameters) {
> super(parameters);
> model.getObject();
> add(new Label("version",
> getApplication().getFrameworkSettings().getVersion()));
> panel = new HomePanel( "homePanel");
> //first time no problem
> panel.addOrReplace( new Label( "test", model ) );
> add(panel);
> //use ame model loaded
> model.getObject();
> //here will detach the model
> panel.addOrReplace( new Label( "test", model ) );
> //load a new model
> model.getObject();
> }
> }
> {code}
> and in panel
> {code:java}
> public class HomePanel extends Panel { Label label; public HomePanel(String
> id) { super( id ); } public HomePanel(String id, IModel<String> model) {
> super( id, model ); label = new Label( "test", model.getObject() ); add(
> label ); } }
> {code}
> in home page html set the panel
> {code:java}
> <span wicket:id="homePanel"> </span>
> {code}
> in panel html
> {code:java}
> <wicket:panel xmlns:wicket="http://wicket.apache.org";>
> User: <span wicket:id="test">dummy name</span><br/>
> </wicket:panel> {code}
> to go further on getModelImpl() (in component.java) we retrieve the first
> element in data object in the picture below we make the detach on the
> HomePanel Object replaced but we see the model detach it the page model
> !image-2022-06-02-08-57-50-406.png!
>
> so why we detach the parent model instead of just let the page do this job ?
>
> !image-2022-06-02-09-01-25-801.png!
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