[WICKET-6348] New FormComponentUpdatingBehavior to replace wantOnSelectionChangedNotifications()

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 8.0.0-M4
• Fix Version/s: 8.0.0-M6
• Component/s: wicket
• Assignee: Sven Meier
• Reporter: Sven Meier
• Created: 29/Mar/17 09:20
• Updated: 24/Jul/20 06:45
• Resolved: 04/Apr/17 15:39

Description

Several form components support notification via normal HTTP request when their value changes in the browser:

• CheckBox
• DropDownChoice
• RadioChoice
• CheckGroup/Check
• RadioGroup/Radio

I propose to move support for this feature into a new behavior "FormComponentUpdatingBehavior".
This has the following advantages:

• having to override #wantOnSelectionChangedNotifications() for #onSelectionChanged() to be triggered wasn't very intuitive
• we minimize the API of these components (the two methods above and #onRequest())
• we can simplify these components by removing from them this non-core concern (a legacy from the pre-Ajax era)
• to use the feature users can add a behavior instead, to have a notification triggered on that behavior (similar to AjaxFormChoiceComponentUpdatingBehavior)
• can be used for text components too

I reused IFormSubmitter to submit the form (for SubmitLink too) so we can simplify Form now:

• no need for the hidden field "_hf_0", used to transport the actual listener url - the form's action is changed instead
• no need for #dispatchEvent(), used to schedule another request handler that triggers the component
• #getJsForInterfaceUrl() is greatly simplified (renamed to #getJsForListenerUrl() now)

Migration effort is manageable:

new CheckBox("id", model) {
	protected boolean wantOnSelectionChangedNotifications() {
		return true;
        }

	protected void onSelectionChanged(Boolean newSelection) {
		// do something, page will be rerendered;
	}
};

... becomes:

new CheckBox("id", model)
.add(new FormComponentUpdatingBehavior() {
	protected void onSelectionChanged() {
		// do something, page will be rerendered;
	}
});

Issue Links

• causes: WICKET-6642 Form.findSubmittingComponent returns null instead of SubmitLink
• relates to: WICKET-6352 Clean-up BaseWicketTester listener invocation/execution
• mentioned in: Page Loading...