Java spring url changes and adds model

I have page in my web application:

http://localhost:8080/user/form/prod/create/0

which has a form attributes of

<c:url var="addAction" value="/user/form/prod/create/${formProd.formHeader.headerId}" ></c:url>
<form:form id="formSubmit" action="${addAction}" modelAttribute="formProd" class="form-horizontal" method="get">

-- Codes for inputs and submit button --

</form:form>

Once the button is clicked it will go through this controller:

@RequestMapping(value = {"/user/form/prod/{type}/{headerId}"}, method = RequestMethod.GET)
public ModelAndView formCreateView(@Validated @ModelAttribute("formProd") FormProd formProd, BindingResult result
		, ModelMap model, Principal principal, @PathVariable(value="headerId") Long headerId, @PathVariable(value="type") String type
		, HttpServletRequest request) {

-- Do some stuff AND return to the same url page http://localhost:8080/user/form/prod/create/0

return new ModelAndView(AuthenticationBase.JSP_USER_FORM_PROD, model);
}

The issue is the url changes to:

http://localhost:8080/user/form/prod/create/0?formHeader.status=DRAFT&formHeader.prodDate=&formHeader.startDateTime=&formHeader.endDateTime=&lookupName=KMM1++++++++++++++++++++++++++&formHeader.line=&formHeader.machine=&formHeader.prodCategoryId=10&formHeader.product=&formHeader.outputMeasureUnitId=13&formHeader.unitPerCarton=&formHeader.standardMachineSpeed=0.0&formHeader.intervalMins=&formHeader.sessionId=

Which also includes my model. Since the url is different, If I click or submit the form again it now shows "whitelabel error page":

Whitelabel Error Page
This application has no explicit mapping for /error, so you are seeing this as a fallback.

Thu Sep 03 11:41:58 SGT 2020
There was an unexpected error (type=Not Found, status=404).

Any idea why the url changes?

This is the by default functionality for GET type mappings.

The GET Method
In GET method the data is sent as URL parameters that are usually strings of name and value pairs separated by ampersands (&). In general, a URL with GET data will look like this:
Example :
http://www.example.com/action?name=Sam&weight=55

Change method type it post and also form method to post and it works.

Change

method = RequestMethod.GET

To

method = RequestMethod.POST

And in view page change form type to POST.

method="POST"

Here you are trying to add the data on click of a button and here you are using the GET method that's why your URL gets change every time when you click on the button.

modify code to below it should work

   <c:url var="addAction" value="/user/form/prod/create/${formProd.formHeader.headerId}" ></c:url>
    <form:form id="formSubmit" action="${addAction}" modelAttribute="formProd" class="form-horizontal" method="POST">

-- Codes for inputs and submit button --

</form:form>

Controller code change

@RequestMapping(value = {"/user/form/prod/{type}/{headerId}"}, method = RequestMethod.POST)
public ModelAndView formCreateView(@Validated @ModelAttribute("formProd") FormProd formProd, BindingResult result
        , ModelMap model, Principal principal, @PathVariable(value="headerId") Long headerId, @PathVariable(value="type") String type
        , HttpServletRequest request) {

-- Do some stuff AND return to the same URL page http://localhost:8080/user/form/prod/create/0

return new ModelAndView(AuthenticationBase.JSP_USER_FORM_PROD, model);
}