[jira] [Commented] (WICKET-7144) Improve Ajax updates of form component panels

["Johan Stuyts (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/WICKET-7144?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18057978#comment-18057978 ] 

Johan Stuyts commented on WICKET-7144:
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[~adelbene], [~bgooren]: I am working on a new attempt. It is not ready yet, but I would like to know what you think. So here is a PR on my own repo: [https://github.com/jstuyts/wicket/pull/1]

Everything works as expected. The difference in code is most visible in the use of `LocalDateTimeField` in [https://github.com/jstuyts/wicket/pull/1/changes#diff-730771ec61758e48121f425b2e820cd141f82c2e2ca09fac199ce1e34e79bbc7]

I did have to change the way to indicate that a `FormComponentPanel` wants to process its children, as the way `LocalDateTimeField` (and `ZonedDateTimeField`) are implemented do not allow using or copying the customizations in the anonymous class created by `newDateField(...)` of `AbstractDateTimeField`. These are the four ways a flag could be implemented:
 * Inheritance (the regular Wicket way): not possible with sub classes of `AbstractDateTimeField`,
 * A flag: possible conflicts with existing sub classes of `FormComponentPanel`, and allocation of a limited set of available flags.
 * An additional attribute: I do not see a lot of additional attributes for state.
 * A metadata key: I chose this one as this has the least impact and is the most compatible.

Note that the introduced method of doing Ajax with `FormComponentPanel`s results in excessive requests. I think this should be addressed, but that this should be done in a separate change as it will help prevent excessive requests in a lot more cases.

Please let me know if using a metadata key is fine, or that a flag or an additional attribute is preferred. Other comments and questions are welcome too. Thanks in advance.

> Improve Ajax updates of form component panels
> ---------------------------------------------
>
>                 Key: WICKET-7144
>                 URL: https://issues.apache.org/jira/browse/WICKET-7144
>             Project: Wicket
>          Issue Type: Improvement
>          Components: wicket-core
>    Affects Versions: 10.4.0
>            Reporter: Johan Stuyts
>            Priority: Major
>              Labels: ajax, form
>         Attachments: WICKET-7144-1.patch
>
>
> Using AjaxFormComponentUpdatingBehavior with FormComponentPanels is cumbersome and therefore error-prone: the client needs to create a sub class of the panel, override the factory methods for the nested form components, add a behavior to the nested components, and then call processInput() on the panel.
> In case of a FormComponentPanel with more than 1 nested form component, it still does not work. The behavior added to a nested component will only submit the data for that nested component and not for the others. The panel uses the converted input of its nested components to determine its converted input (which is used to update the model). But the other components wll not have converted input, so the panel cannot determine its own converted input. The model of the panel will not contain the correct value when onUpdate(...) of the behavior is called.
> Ajax updates of FormComponentPanels can be made more developer-friendly by:
>  * Allowing panels (or sub classes) to indicate that they want to their children to process their input in an Ajax update.
>  * Modifying AjaxFormComponentUpdatingBehavior to detect FormComponentPanels that have indicated that their children should process their input, and:
>  ** Enable recursive serialization in the Ajax attributes, so all data of a FormComponentPanel is available in an Ajax update. 
>  ** Telling these panels to tell their children to process their input in an Ajax update.
> The needed changes are attached in a patch, and can be viewed here: [https://github.com/apache/wicket/compare/master...jstuyts:wicket:form-component-panel-ajax-update]
> The changes are backward compatible and won't affect existing code, unless the signatures of the new methods of FormComponentPanel have been used.



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