Repeaters | Apache Wicket

A repeater renders its markup once for each of its children. It writes no tag of its own: every child renders with the repeater’s tag as if it were the child’s. All repeaters extend AbstractRepeater, which calls onPopulate() before each render to create or update the children.

Repeaters at a glance

Repeater	Module	Data from	You implement	Item	Item model	Pageable
`RepeatingView`	core	the children you add	nothing	any component, id from `newChildId()`	none of its own	no
`RefreshingView<T>`	core	`getItemModels()`	`getItemModels()`, `populateItem(Item<T>)`	`Item<T>`	the model from the iterator	no
`ListView<T>`	core	a `List<T>` or `IModel<List<T>>`	`populateItem(ListItem<T>)`	`ListItem<T>`	`ListItemModel`: element n of the list	no
`PropertyListView<T>`	core	as `ListView`	`populateItem(ListItem<T>)`	`ListItem<T>`	`CompoundPropertyModel` around `ListItemModel`	no
`PageableListView<T>`	core	as `ListView`, plus items per page	`populateItem(ListItem<T>)`	`ListItem<T>`	`ListItemModel`	yes
`Loop`	core	an `int` or `IModel<Integer>`	`populateItem(LoopItem)`	`LoopItem`	none	no
`DataView<T>`	core	`IDataProvider<T>`	`populateItem(Item<T>)`	`Item<T>`	`IDataProvider.model(T)`	yes
`GridView<T>`	core	`IDataProvider<T>`	`populateItem(Item<T>)`, `populateEmptyItem(Item<T>)`	`Item<T>` in rows of `setColumns(n)` cells	`IDataProvider.model(T)`	yes
`DataGridView<T>`	extensions	`IDataProvider<T>` and a list of `ICellPopulator<T>`	the populators	a row `Item<T>` with a cell per populator	`IDataProvider.model(T)`	yes
`DataTable<T, S>`	extensions	`IDataProvider<T>` and a list of `IColumn<T, S>`	the columns	a `<tr>` with a `<td>` per column	`IDataProvider.model(T)`	yes
`DefaultDataTable<T, S>`	extensions	`ISortableDataProvider<T, S>` and columns	the columns	as `DataTable`, rows are `OddEvenItem`	`IDataProvider.model(T)`	yes
`AjaxFallbackDefaultDataTable<T, S>`	extensions	as `DefaultDataTable`	the columns	as `DefaultDataTable`	`IDataProvider.model(T)`	yes, with Ajax
`NestedTree<T>`, `DefaultNestedTree<T>`	extensions	`ITreeProvider<T>`	`newContentComponent` (for `NestedTree`)	nested branches	`ITreeProvider.model(T)`	no
`TableTree<T, S>`, `DefaultTableTree<T, S>`	extensions	`ITreeProvider<T>` and columns	the columns, and `newContentComponent` (for `TableTree`)	table rows, one per visible node	`ITreeProvider.model(T)`	through its `DataTable`, `getTable()`

When items are re-created

Repeater	On every render	Keeps existing items when
`RepeatingView`	does nothing; the children stay until you remove them	always
`ListView`, `PropertyListView`, `PageableListView`	removes all items and creates new ones	`setReuseItems(true)`: keeps items by index, creates missing ones, removes those past the end
`Loop`	removes all items and creates new ones	never
`RefreshingView`, `DataView`, `GridView`, `DataGridView`, `DataTable`	asks the `IItemReuseStrategy` for the items	the strategy keeps them; `ReuseIfModelsEqualStrategy` keeps items whose model equals a new model

populateItem runs only for newly created items. Form components inside a repeater need kept items, or they lose their input and error messages after a failed submit.

Item reuse strategies

Strategy	Behavior
`DefaultItemReuseStrategy`	the default; creates a new item for every model, every render
`ReuseIfModelsEqualStrategy`	keeps an existing item when its model `equals` a model returned for this render; the models must implement `equals` and `hashCode`
your own `IItemReuseStrategy`	implements `getItems(factory, newModels, existingItems)`

Set a strategy with setItemReuseStrategy on RefreshingView and its subclasses, on DataTable and on TableTree. getInstance() returns the shared instance of either built-in strategy.

Item classes

Class	Extends	Used by	Adds
`ListItem<T>`	`WebMarkupContainer`	`ListView`	`getIndex()`
`OddEvenListItem<T>`	`ListItem<T>`	your `ListView.newItem` override	`class="odd"` or `class="even"` by default
`Item<T>`	`ListItem<T>`	`RefreshingView` and subclasses	`getPrimaryKey()`
`OddEvenItem<T>`	`Item<T>`	`DefaultDataTable` rows	`class="odd"` or `class="even"` by default; the class names are resource keys
`LoopItem`	`WebMarkupContainer`	`Loop`	`getIndex()`

Override newItem in a repeater to use another item class.

Data providers

Type	Module	Description
`IDataProvider<T>`	core	`iterator(first, count)` returns one page of objects, `size()` the total, `model(T)` a model per object; `detach()` is called at the end of the request
`ListDataProvider<T>`	core	serves a `List<T>` held in the provider; `model(T)` returns a `Model`
`EmptyDataProvider<T>`	core	always empty; `getInstance()`
`ISortableDataProvider<T, S>`	extensions	an `IDataProvider` that is also an `ISortStateLocator<S>`
`SortableDataProvider<T, S>`	extensions	base class keeping a single sort property; `setSort(property, order)`, `getSort()` returns a `SortParam<S>` with `getProperty()` and `isAscending()`
`ITreeProvider<T>`	extensions	`getRoots()`, `hasChildren(T)`, `getChildren(T)`, `model(T)`
`SortableTreeProvider<T, S>`	extensions	an `ITreeProvider` with a sort state

Paging

Type	Description
`IPageable`	`getCurrentPage()`, `setCurrentPage(long)`, `getPageCount()`
`IPageableItems`	adds `getItemCount()`, `getItemsPerPage()`, `setItemsPerPage(long)`
`AbstractPageableView<T>`	base of `DataView` and `GridView`; shows every item until `setItemsPerPage` is called
`PagingNavigator`	panel with links to the first, previous, numbered, next and last pages of an `IPageable`
`AjaxPagingNavigator`	the same with Ajax links; updates the nearest parent of the pageable with `setOutputMarkupId(true)`
`PagingNavigation`	the numbered links alone, as a `Loop`
`NavigatorLabel`	shows “Showing 1 to 10 of 42” for an `IPageableItems`; the text is the resource `NavigatorLabel`

Tables

DataTable is attached to a <table> tag and generates its caption, <colgroup>, <thead>, <tbody> and <tfoot>.

Column class	Description
`IColumn<T, S>`	`getHeader(id)`, `getSortProperty()`, `populateItem(cellItem, componentId, rowModel)`
`AbstractColumn<T, S>`	base class with a display model for the header and an optional sort property
`LambdaColumn<T, S>`	shows the result of a function on the row object
`PropertyColumn<T, S>`	shows a property of the row object by property expression
`HeaderlessColumn<T, S>`	a column without header text
`IStyledColumn<T, S>`	adds `getCssClass()` for the cells
`FilteredPropertyColumn`, `TextFilteredPropertyColumn`, `ChoiceFilteredPropertyColumn`	property columns with a filter field for `FilterToolbar`
`AbstractExportableColumn`	a column that `ExportToolbar` can export
`TreeColumn`	the column of a `TableTree` that shows the node with its junction

Columns that return a sort property get a sortable header in HeadersToolbar.

Toolbar	Added by	Description
`HeadersToolbar`	`DefaultDataTable`, top	column headers; sortable headers use `OrderByBorder`
`AjaxFallbackHeadersToolbar`	`AjaxFallbackDefaultDataTable`, top	the same, sorting with Ajax
`NavigationToolbar`	`DefaultDataTable`, top	a `PagingNavigator` and a `NavigatorLabel`; hidden when there is one page
`AjaxNavigationToolbar`	`AjaxFallbackDefaultDataTable`, top	the same with an `AjaxPagingNavigator`
`NoRecordsToolbar`	`DefaultDataTable`, bottom	a row with a message when there are no rows
`FilterToolbar`	you	a row of filter fields, inside a `FilterForm`
`ExportToolbar`	you	links to download the data, for example as CSV with `CSVDataExporter`

Add toolbars with addTopToolbar(toolbar) and addBottomToolbar(toolbar).

Sort links

Component	Description
`OrderByLink`	a link that sets the sort property of an `ISortStateLocator`
`OrderByBorder`	a border around a header that adds an `OrderByLink` and CSS classes for the sort state
`AjaxOrderByLink`, `AjaxFallbackOrderByBorder`	the same with Ajax

Use these to make the headers of a DataView sortable when you write the table markup yourself.