Spring MVC - Set an actionURL parameter with Javascript

Question

Is it possible to dynamically set a Spring MVC portlet:actionURL portlet:param using javascript? I have tried with the following code, but the id value always comes across as null to the controller. I have verified that setting the portlet:param manually passes the value correctly:

<portlet:param name="id" value="2" />

I have also verified the value in the javascript is being set correctly and is not null.

(Note: I've changed the variable names, etc. from the original code to simplify it and obfuscate it since it is my employer's code.)

JSP:

<portlet:actionURL var="modifyURL">
    <portlet:param name="do" value="modify" />
    <portlet:param name="id" value="${model.id}" />
</portlet:actionURL>

...

<form:form action="${modifyURL}" id="modifyForm" modelAttribute="model">
    <form:hidden path="id" id="id" />
</form:form>

Javascript called when the update URL is clicked:

function update() {
    document.forms[0]["id"].value = selectedId;
    document.forms[0].submit();
}

Controller:

@RequestMapping(params = {"do=modify"})
public void modify(@ModelAttribute("model") Model model, 
    @RequestParam(value = "id", required=true) Long id,
    ActionRequest request, ActionResponse response,
    SessionStatus sessionStatus, ModelMap modelMap)  {
....

Answer 1

A co-worker figured it out. It looks like you just have to add the parameter to the action within the javascript and not include it in the actionURL or form.

JSP:

<portlet:actionURL var="modifyURL">
    <portlet:param name="do" value="modify" />
</portlet:actionURL>

...

<form:form action="${modifyURL}" id="modifyForm" modelAttribute="model" method="POST">
</form:form>

Javascript called when the update URL is clicked:

function update() {
    $("modifyForm").action = '${modifyURL}&id='+selectedId;
    $("modifyForm").submit();
}