Dynamic form - multiple form:input tags

[Vladimir Kroupa]

Hello,
I have a problem with dynamic forms in Spring 2.5 that I was unable to solve myself.
I have a collection of Items. I would like to display a page that has an input form with submit button next to each Item.
Something like this:

<form:form method="POST" commandName="itemCommand">
    <c:forEach items="${items}" var="item">
         item: ${item.name}
        <form:input path="requiredAmount">
        <form:hidden path="itemId" />
        <input type="submit" value="Order it!" />
    </c:forEach>   
</form:form>

I cannot use a single command object with fields for each Item. Would it be possible to use a Map inside the command object and bind it somehow to the form:input tags?

Thanks for any tips.
Vladimir

[Costi Ciudatu]

Have a look at <form:radiobuttons/>

[Vladimir Kroupa]

Thanks for the reply.
I've checked the documentation for <form:radiobuttons> and <form:checkboxes> and I've only found this:
In the case where you use a Map, the map entry key will be used as the value and the map entry's value will be used as the label to be displayed.
Could you please tell me a little more about what should I be looking for?

[Vladimir Kroupa]

I was able to bind the map in a way that works for displaying the map values in a form (GET). However, the binding doesn't work when I try to submit the form.

When I try to submit, I get NullValueInNestedPathException: Invalid property 'cartMap[163840]' of bean class [shop.web.COs.ShoppingCartCO]: Value of nested property 'cartMap[163840]' is null.
But when I try to access the cartMap[163840] entry directly in JSP, it works.

This is what my JSP file looks like:

            <form:form method="POST" commandName="shoppingCartCO">                 
                    test: ${shoppingCartCO.cartMap[163840].product.name}
                    <c:forEach items="${shoppingCartCO.cartMap}" var="item">
                            ${shoppingCartCO.cartMap[item.key].product.name}
                            <form:input path="cartMap[${item.key}].amount" /> pcs
                    </c:forEach>
                    <input type="submit" value="Update" />
            </form:form>

The controller code should be OK:

    @RequestMapping( method = RequestMethod.GET )
    public String setupForm( ModelMap model, HttpServletRequest request ) {

        /* retrieving a collection of OrderItems - not important
           ...
        */
        Map cartMap = new HashMap<Long, OrderItem>();
        for ( OrderItem item : cart ) {
            cartMap.put( item.getId(), item );
        }

        /* ShoppingCartCO is the class I use as the command object.
           It only has a getter and a setter for the cartMap property. */
        ShoppingCartCO shoppingCartCO = new ShoppingCartCO();
        shoppingCartCO.setCartMap( cartMap );
        model.addAttribute( "shoppingCartCO", shoppingCartCO );
        return "showcart";
    }

I'll be grateful for any tips. I have a book on Spring and I've searched the documentation, but I haven't find anything that would help.

[Costi Ciudatu]

Let me first try to clarify your issue just to make sure I got the point:

1) You want to be able to update single values in that list of products.
If so, you should consider creating a form instance for every element item; otherwise, every update button will send all the items and their values to the server. In other words, every "Update" button will just behave like a single "Update All" button.
2) You don't actually need a map there, a mere list would be enough (you have the ID as a property of that bean, so you don't need to store it in a map key). Not to mention that HashMap does not guarantee the order of the elements.
3) It looks like you have an empty command object instantiated on submit, with a null cartMap reference. How do you define that CO as command object for your controller ? You may need to initialize the cartMap in the command object's constructor. Can you post the whole code for the controller (especially the submit handler) and probably the spring descriptors ?