Passing a parameter to a controller

[Alejandro Barrero]

I have code that works.
Html

th:href="@{/GetLicenses(userName=${theUser},fullName=${fullName})}"

Controller

@GetMapping("/GetLicenses")
public String licenses(LicensesRequest licensesRequest, @RequestParam String userName, @RequestParam String fullName, Model map) {

But very similar code is not working
Html

<form class="form" th:action="@{/ModifyUser(fullName=${fullName})}" method="GET">

Controller

@GetMapping("/ModifyUser")
public String modifyUser(String passedValue, @RequestParam String fullName, Model map) {

In the browser I get the message "HTTP Status 400 – Bad Request".
In Eclipse I get the message
2020-06-26 10:49:50.686  WARN 13780 --- [nio-8080-exec-4] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved [org.springframework.web.bind.MissingServletRequestParameterException: Required String parameter 'fullName' is not present]

[Alejandro Barrero]

I changed GET tp POST and now it works. I am stumbled.