How to nest forms

As you might already know, HTML doesn’t allow to have nested forms. However with Wicket we can overcome this limitation by adding one or more form components to a parent form.

This can be useful if we want to split a big form into smaller ones in order to reuse them and to better distribute responsibilities among different components. Forms can be nested to an arbitrary level:

<form wicket:id="outerForm">
    ...
    <form wicket:id="innerForm">
        ...
        <form wicket:id="veryInnerForm">
            ...
        </form>
    </form>
</form>

When a form is submitted also its nested forms are submitted and they participate in the validation step. This means that if a nested form contains invalid input values, the outer form won’t be submitted. On the contrary, nested forms can be singularly submitted without depending on the status of their outer form.

To submit a parent form when one of its children forms is submitted, we must override its method wantSubmitOnNestedFormSubmit and make it return true.