better way for dynamic forms with Spring?

Question

What I wonder is if there\'s a easier/better way to handle dynamic forms (adding form items to the dom via js) when using SpringMVC and Spring forms?

Imaging having

Answer 1

You could use the following

public class InvoiceController extends SimpleFormController {

    protected void initBinder(HttpServletRequest request, ServletRequetDataBinder binder) throws Exception {
        binder.registerCustomEditor(List.class, "lineItems", new CustomCollectionEditor(List.class)() {
            protected Object convertElement(Object lineItem) {
                LineItem li = (LineItem) lineItem;

                // StringUtils is a jakarta Commons lang static class
                return (StringUtils.isBlank(li.getProductName())) ? null : li;
            }

        });
    }

}

Then in onBind method, you remove null references according to:

protected void onBind(HttpServletRequest request, Object command, BindException bindException) throws Exception {
    Invoice invoice = (Invoice) command;

    invoice.getLineItems().removeAll(Collections.singletonList(null));
}    

Regards,

Answer 2

I've implemented a tutorial that might help you solve this using jQuery on the client side and Springs AutoPopulating list for you form backing objects.

http://eggsylife.co.uk/2009/11/30/spring-forms-dynamic-lists-and-ajax/

EDIT Link from Webarchive https://web.archive.org/web/20160729163958/http://eggsylife.co.uk/2009/11/30/spring-forms-dynamic-lists-and-ajax/

Answer 3

I've been struggling with this problem today and figured out some solution described here.

Answer 4

I've found that also decorating with a GrowthList is necessary to avoid some errors when adding/setting items in JSP. (Also created a custom SpringList impl. that basically does the double decoration.)

lineItems = GrowthList.decorate(ListUtils.lazyList(new ArrayList<LineItem>(), FactoryUtils.instantiateFactory(LineItem.class)));

I agree. The problem is certainly removing items.

What you can do is use the spring marker syntax in the html. So if you remove an item (at index 2 for example) from the list using javascript, you would then mark that index with:

<input type="hidden" name="_lineItems[2]">

Then when the form is submitted spring will see the marker and put in an empty item (based on the lazylist factory) for lineItems2 instead of ignoring it.