Wicket in Action

A comprehensive guide for Java developers building Wicket-based web applications

Building a ListEditor form component

October 15th, 2008 by ivaynberg

A common question on Wicket mailing lists is “Why doesn’t my ListView work as expected in a Form?”. There can be many possible answers, but the core issue is that ListView was never designed to work as a form component. ListView is great when it comes to displaying a list of elements, but in order to be a good citizen in Wicket’s form processing a list editor should possess the following features:

  • Preserve component hierarchy that represents list items - this means that components the user added to represent an item in the list should be preserved even if list items are shuffled around. This will allow things like feedback messages and error indicators to work seamlessly and transparently
  • Implement atomic form updates - this is perhaps the most important feature. If the user moves an item up or down in the list this change should not be reflected in the model object until the form is submitted. Same goes for actions such as item additions and removals.
  • Should be reusable for different usecases

Surprisingly, implementing such a component is trivial. We will start by implementing the ListEditor itself and its one supporting class: ListItem, and later move on to implementing a Remove button. As always the fully functional sample project will be attached at the bottom.
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System Mobile

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