Dynamic list item index with Spring Form

For decorated unordered lists like this:

private List<MyListItem> items = 开发者_Python百科LazyList.decorate(new ArrayList(),
        FactoryUtils.instantiateFactory(MyListItem.class));

Is it compulsory to name the attributes in the form with an index number? such as:

<form:input path="items[1]" />
<form:input path="items[2]" />

Why can't I provide the two brackets like in PHP?

item[]

Because while dynamically creating the input list with DOM would be a problem to deal with item deletions...

---

The same way you ask why Spring does not support a generic kind of pattern such as item[], you could also be asking why your collection is not ordered according to the order of items shown by your form. Keep in mind: java.util.List is an ordered collection, so you must tell Spring where each item in the list must be inserted.

Workaround

1º option

Create an AutoPopulatingList as follows

private List<Item> items = new AutoPopulatingList(
    new ElementFactory() {
        public Object createElement(int index) throws ElementInstantiationException {
             /**
               * Any removed item will be handled as null. 
               * So we just remove any nullable item before adding to our List
               * By using the following statement
               */
             items.removeAll(Collections.singletonList(null));

             return new Item();
        }
    });

2º option

Because Spring is open-source, you can create a custom BeanWrapperImpl. Behind the scenes, BeanWrapperImpl is responsible to populate your bean. Next, compile your custom Spring MVC

---

You could acces your variables like:

<form:input path="${item[0]}" />
<form:input path="${item[1]}" />

Another way is:

<c:forEach items="${items}" var="item">
    <form:input path="${item}" />
</c:forEach>