Pass loop variable from Freemarker template to Spring controller - spring-mvc

Question

I am listing objects in a table in my view. I want to be able to edit an object using a button in the table.
<#list products as product>
<tr>
<td>${product.productName}</td>
<td>${product.price}</td>
<td>${product.quantity}</td>
<td>
<form name="product" method="post" action="/product/edit">
<input type="submit" name="submit" value="Edit this product"/>
</form>
</td>
</tr>
</#list>
The object then should be passed to a controller method:
#RequestMapping(value="/edit", method = RequestMethod.POST)
public ModelAndView edit(#ModelAttribute("product") Product product){
ModelAndView mav = new ModelAndView("product/edit");
mav.addObject("product", product);
return mav;
}
However, the product obtained by the edit method is null. How do I fix this? I tried to bind the product inside form using the code below, but that did not work either.
<form name="product" method="post" action="/product/edit">
<#spring.bind "product" />
<input type="hidden" name="${spring.status.expression}" value="${spring.status.value}"/>
<input type="submit" name="submit" value="Edit this product"/>
</form>
I want to use the POST method.

Answer 1

I would like to suggest a different approach. If I'm not mistaken you just want to pick an object for later editing - you don't really edit it in that very view.
If so, all you have to do is to pass an identifier of your object to your controller, but not the selected object itself.
If not, you should give us the hole story and provide the rest of the view as well.
Assuming I'm right the next question is why you need to use a form submission at all. Passing an id is best done by links - either as parameter or, if you follow REST-style, as part of the URI itself:
<!-- Link parameter -->
<#list products as product>
<tr>
<td>${product.productName}</td>
<td>${product.price}</td>
<td>${product.quantity}</td>
<td>
Edit ${product.productName}
</td>
</tr>
</#list>
<!-- REST-style -->
...
Edit ${product.productName}
...
productName isn't a good id of course. If products is a list (meaning, java.util.List) the index of the list is handy. Even in a HashMap or Set I'd create a unique id instead of using the product name.
Now that you can identify your object, select it in the backing code for later editing, but not in the view.
You'll find loads of examples of how to get link parameters in a controller. So, no need to go into detail here.
If however you insist on using a form and a POST-method then do it like this:
<form method="post" action="/product/edit">
<#list products as product>
<tr>
<td>${product.productName}</td>
<td>${product.price}</td>
<td>${product.quantity}</td>
<td>
<button value="${product.productName}" name="product" type="submit">Edit ${product.productName}</button>
</td>
</tr>
</#list>
</form>
Note that this won't work for older IE browsers (below Ver. 10), because they don't return the value, but everything that is inside the button tag.
Hidden inputs and a single submit button won't help at all, because all inputs are submitted and using different forms is not the way either.