Ajax behaviors | Apache Wicket

An Ajax behavior adds Ajax to a component that has none: it listens to a browser event on the component’s element and calls a method on the server with an AjaxRequestTarget. Every behavior makes its component output a markup id. All Ajax behaviors extend AbstractDefaultAjaxBehavior, whose updateAjaxAttributes(AjaxRequestAttributes) you override to change how the request is sent; see Change how an Ajax request is sent.

Event and form behaviors

All in wicket-core, package org.apache.wicket.ajax and its form subpackage.

Class	What it does	Callback you override
`AjaxEventBehavior`	Calls the server when a browser event, such as `click` or `keyup`, fires on the component. Takes the event name; an `on` prefix is cut off.	`onEvent(AjaxRequestTarget)`
`AjaxFormComponentUpdatingBehavior`	On the given event, converts and validates the input of its form component and updates the model, without submitting the form.	`onUpdate(AjaxRequestTarget)`, `onError(AjaxRequestTarget, RuntimeException)`
`OnChangeAjaxBehavior`	`AjaxFormComponentUpdatingBehavior` on `input` and `change` for text fields and text areas, on `change` for other components.	`onUpdate(AjaxRequestTarget)`
`AjaxFormChoiceComponentUpdatingBehavior`	Updates the model of a group of choices on `change`: `RadioChoice`, `CheckBoxMultipleChoice`, `RadioGroup`, `CheckGroup`.	`onUpdate(AjaxRequestTarget)`
`AjaxFormSubmitBehavior`	Submits a form with Ajax when the event fires. Without a form argument it submits the form the component is in.	`onSubmit(AjaxRequestTarget)`, `onError(AjaxRequestTarget)`, `onAfterSubmit(AjaxRequestTarget)`
`AjaxFormValidatingBehavior`	Submits the form on the given event and refreshes every feedback panel on the page. Add it to a form or to a component in a form.	`onSubmit`, `onError`, `onAfterSubmit`, all with an `AjaxRequestTarget`, optional
`FilesSelectedBehavior`	Reports the files picked in a `FileUploadField`, before they are uploaded.	`onSelected(AjaxRequestTarget, List<FileDescription>)`
`AjaxPreventSubmitBehavior`	Stops Enter in a text field from submitting the form. Runs in the browser only.	none
`AbstractDefaultAjaxBehavior`	Base class for your own Ajax behavior. `getCallbackScript()` and `getCallbackFunction(CallbackParameter...)` give the JavaScript that calls it.	`respond(AjaxRequestTarget)`

AjaxFormComponentUpdatingBehavior does not work for radio buttons and check boxes in a group; use AjaxFormChoiceComponentUpdatingBehavior there. Override its getUpdateModel() to return false when you want the input validated but the model left alone.

AjaxFormSubmitBehavior does not prevent the browser’s default action. On an <input type="submit"> or a <button> in the form, call attributes.setPreventDefault(true) in updateAjaxAttributes, or the form is submitted twice.

When shouldTriggerJavaScriptSubmitEvent() returns true, on AjaxFormSubmitBehavior, AjaxButton or AjaxFallbackButton, the behavior fires a JavaScript submit event on the form before it sends the request, so that the form’s submit handlers run. A handler that cancels the event cancels the Ajax request. The default is false.

Timers

Class	What it does	Callback you override
`AbstractAjaxTimerBehavior`	Calls the server at a fixed interval, given as a `Duration`. `stop(target)` and `restart(target)` pause and resume it.	`onTimer(AjaxRequestTarget)`
`AjaxSelfUpdatingTimerBehavior`	Re-renders its own component at a fixed interval.	`onPostProcessTarget(AjaxRequestTarget)`, optional

Label clock = new Label("clock", () -> LocalTime.now().withNano(0));
clock.add(new AjaxSelfUpdatingTimerBehavior(Duration.ofSeconds(1)));
add(clock);

Browser information

Class	What it does	Callback you override
`AjaxClientInfoBehavior`	Collects screen size, time zone and other browser properties shortly after the page loads, with a timer.	`onClientInfo(AjaxRequestTarget, WebClientInfo)`
`AjaxOnDomReadyClientInfoBehavior`	The same, sent when the DOM is ready.	`onClientInfo(AjaxRequestTarget, WebClientInfo)`
`AjaxNewWindowNotifyingBehavior`	Detects that the page instance was opened in a second window or tab of the same session.	`onNewWindow(AjaxRequestTarget)`

Behaviors in wicket-extensions

Class	What it does	Callback you override
`AjaxDownloadBehavior`	Starts a download of a resource from an Ajax callback with `initiate(target)`, without leaving the page.	`onBeforeDownload(IPartialPageRequestHandler)`, `onDownloadSuccess`, `onDownloadFailed`, `onDownloadCompleted`, all with an `AjaxRequestTarget`
`AjaxFileDropBehavior`	Uploads files dropped onto the component.	`onFileUpload(AjaxRequestTarget, List<FileUpload>)`, `onError(AjaxRequestTarget, FileUploadException)`
`AutoCompleteBehavior<T>`	Adds a suggestion list to any text field; `AutoCompleteTextField` uses it.	`getChoices(String input)`
`AjaxIndicatorAppender`	Renders a hidden busy indicator image after its component. See Show that a request is running.	none

Call listeners

A call listener runs JavaScript at the stages of one Ajax request. You add it to attributes.getAjaxCallListeners(); see React to Ajax requests in JavaScript.

Class	Module	What it does
`AjaxCallListener`	wicket-core	Base class with chainable setters: `onBefore`, `onPrecondition`, `onBeforeSend`, `onAfter`, `onSuccess`, `onFailure`, `onComplete`, `onInit`, `onDone`.
`AjaxDisableComponentListener`	wicket-extensions	Sets `disabled` on the component while the request runs.
`CancelEventIfAjaxListener`	wicket-core	Cancels the browser’s default action when the Ajax call was made. `AjaxFallbackLink` uses it.

Lambda factory methods

These static methods create a behavior from a lambda instead of an anonymous subclass. The lambda receives the AjaxRequestTarget.

Class	Factory method
`AjaxEventBehavior`	`onEvent(String event, SerializableConsumer<AjaxRequestTarget>)`
`AjaxFormComponentUpdatingBehavior`	`onUpdate(String event, SerializableConsumer<AjaxRequestTarget>)`
`OnChangeAjaxBehavior`	`onChange(SerializableConsumer<AjaxRequestTarget>)`
`AjaxFormChoiceComponentUpdatingBehavior`	`onUpdateChoice(SerializableConsumer<AjaxRequestTarget>)`
`AjaxFormSubmitBehavior`	`onSubmit(String event, SerializableConsumer<AjaxRequestTarget>)`
`AbstractAjaxTimerBehavior`	`onTimer(Duration, SerializableConsumer<AjaxRequestTarget>)`
`AjaxSelfUpdatingTimerBehavior`	`onSelfUpdate(Duration, SerializableConsumer<AjaxRequestTarget>)`
`AjaxNewWindowNotifyingBehavior`	`onNewWindow(SerializableConsumer<AjaxRequestTarget>)`
`AjaxClientInfoBehavior`	`onClientInfo(SerializableBiConsumer<AjaxRequestTarget, WebClientInfo>)`
`AjaxOnDomReadyClientInfoBehavior`	`onClientInfo(SerializableBiConsumer<AjaxRequestTarget, WebClientInfo>)`
`FilesSelectedBehavior`	`onSelected(SerializableBiConsumer<AjaxRequestTarget, List<FileDescription>>)`

nameField.add(OnChangeAjaxBehavior.onChange(target -> target.add(preview)));

Write Ajax handlers as lambdas shows them in use.