Question

I use Spring MVC 3.0 and JSP. I have an object:

public class ObjectWrapper {
    private List<SomeTO> someTOs;
}

Class SomeTO contains fields like name and id. How can I create a form on which an user can dynamically add to list of SomeTO? I googled it and found something about spring:bind, but it’s unclear for me.

Answer 1

In the form backing method, set the list to a LazyList which is part of the apache commons collection library.

Factory notificationFactory = new Factory() {
       public Object create() {
            SomeTO rtVl = new SomeTO();
            return rtVl;
        }
 };
myFormBacking.setSomeTOs(LazyList.decorate(myFormBacking.getSomeTOs));

Then on your form, when you send the data to the server you can do it like this

<input name="someTOs[0].name" value="" />

And if your using

<%@taglib prefix="form" uri="http://www.springframework.org/tags/form" %>

then you can simply go.

<form:input path="someTOs[0].name" />

Before posting the data to the server, to make pruning easier, set the number of elements in the collection. So if the user added 5 TOs, then send that length value in the form post.

ON the server now, you must prune the list before you save it. Here is the function for pruning

public List<SomeTOs> pruneList(List<SomeTOs> unpruned,int expectedLength){
    List<SomeTOs> rtVl = new ArrayList<SomeTOs>();
    for (int i = 0; i < unpruned.length && expectedLength; ++i){
         rtVl.add(unpruned.get(i);
    }
    return rtVl;
}

Here is the use of the prune function in the on submit (before save)

wrapper.setSomeTOs(pruneList(wrapper.getSomeTOs(),Integer.parseInt(request.getParameter("expectedLength)));