Spring Cloud Openfeign Can I not use 'final' when sending a POST request with Feign in Spring Boot?

ext {
    set('springCloudVersion', "2022.0.3")
}

    id 'org.springframework.boot' version '3.1.1'
implementation 'org.springframework.cloud:spring-cloud-starter-openfeign'

In the request below, if 'final' is attached to the field variable of the RequestParam object, the request is not properly delivered. What is the reason for this?

@FeignClient(name = "client", url = "https://kauth.kakao.com")
public interface RequestAccessToken {

    @PostMapping(
            "/oauth/token?grant_type=authorization_code&client_id={CLIENT_ID}&code={CODE}")
    UserInfoResponse kakaoAuth(
            @PathVariable("CLIENT_ID") String clientId,
            @PathVariable("CODE") String code);


    @PostMapping(path = "/oauth/token", consumes = MediaType.APPLICATION_FORM_URLENCODED_VALUE)
    UserInfoResponse unlinkUser(@RequestBody RequestParam RequestParam);
}


@Getter
@Setter
@AllArgsConstructor
public class RequestParam {
    String grant_type;
    String client_id;
    String redirect_uri;
    String code;
}

Comment From: kbaluc

look here - https://github.com/OpenFeign/feign-form/issues/77.

Comment From: OlgaMaciaszek

Closing in favour of https://github.com/OpenFeign/feign-form/issues/77. This is an upstream issue.