Spring 3 checkbox list objects have null properties - spring-mvc

Question

I may be hopelessly lost here, but having come from a MVC.NET world I cannot for the life of me figure this one out. I'm not getting any error messages, but all object properties submitted on a form submission are null. The objects themselves are not null, just their properties.
All I want to do is have a series of objects, represented by checkboxes on the form, after the forms submits. It's a little tricky as you can can see because of a nested list arrangement. The view renders perfectly on the GET request, but seems to forget everything when posted to the server. Does anyone have any examples of such a set-up? Could anyone suggest why all my objects loose their bindings?
My Controller:
#RequestMapping(value="/Search", method = RequestMethod.GET)
public String search(Model model)
{
Period periods = new Period();
SearchModel search = new SearchModel();
search.periods = periods.BuildPeriodList();
model.addAttribute("periods", periods.BuildPeriodList());
model.addAttribute(search);
return "search";
}
#RequestMapping(value = "/Search", method = RequestMethod.POST)
public String search(#ModelAttribute("searchModel") SearchModel search, BindingResult result)
{
System.out.println(Arrays.deepToString(search.periods));
return "search";
}
My View:
<div id="searchPage">
<div id="searchForm">
<form:form action="Search" method="post" modelAttribute="searchModel">
<h2>Search</h2>
<h2>Periods</h2>
<c:forEach items="${periods}" var="period" varStatus="index">
<form:checkbox path="periods[${index.count - 1}]" id="${period.name}" name="${period.name}" value="${period.name}"/>
<label for="${period.name}">${period.displayName}</label>
<div class="subPeriods">
<c:forEach items="${period.subPeriods}" var="subPeriod" varStatus="subIndex">
<form:checkbox path="periods[${subIndex.count - 1}].subPeriods" id="${subPeriod.name}" name="${subPeriod.name}" value="${period.name}"/>
<label for="${subPeriod.name}">${subPeriod.displayName}</label>
</c:forEach>
</div>
</c:forEach>
<div class="clear"></div>
<h2>Extras</h2>
<form:checkbox path="hasImage" name="hasImage" id="hasImage"></form:checkbox>
<label for="hasImage">Image</label>
<form:checkbox path="hasPaper" name="hasPapaer" id="hasPapaer"></form:checkbox>
<label for="hasPaper">Paper Data</label>
<form:checkbox path="hasExtended" name="hasExtended" id="hasExtended"></form:checkbox>
<label for="hasExtended">Extended Info</label>
<input type="submit" name="search" value="Search"></input>
</form:form>
</div>
<div id="searchResults">
</div>
<div class="clear"></div>

Answer 1

It's due to some of your checkboxes being bound to your "periods" model, while others being bound to your SearchModel model. The path attribute of the form:checkbox element tells how to bind the information.
Either include this within your SearchModel, or have another #ModelAttribute("periods") in your POST method.
I'd recommend sticking to one model, plus I'm not sure if you can have more than one #ModelAttribute in a controller method, something to try, though.