Have some request

@FeignClient(
        name = "someServer",
        url = "someUrl",
        configuration = FeignProxyConfiguration.class)
public interface ServerFeign {

    @PostMapping(produces = MediaType.TEXT_PLAIN_VALUE)
    ResponseEntity<String> sendCode(@RequestHeader HttpHeaders headers, @RequestBody String request);

private HttpHeaders getHttpHeaders() {
        var headers = new HttpHeaders();
        headers.add(HttpHeaders.CONTENT_TYPE, "application/x-www-form-urlencoded");
        return headers;
    }


public class FeignProxyConfiguration {

    @Value("${proxy.host:host}")
    private String proxyHost;

    @Value("${proxy.port:8080}")
    private String proxyPort;

    @Value("${proxy.user:user}")
    private String proxyUser;

    @Value("${proxy.password:password}")
    private String proxyPassword;

    @Bean
    public feign.Client feignClient() {
        OkHttpClient okHttpClient;
        Proxy proxy = new Proxy(Proxy.Type.HTTP, new InetSocketAddress(proxyHost, Integer.parseInt(proxyPort)));
        okHttpClient = new OkHttpClient.Builder()
                .proxy(proxy)
                .proxyAuthenticator(authenticator())
                .build();
        return new feign.okhttp.OkHttpClient(okHttpClient);
    }

    private okhttp3.Authenticator authenticator() {
        return (route, response) -> {
            String credential = okhttp3.Credentials.basic(proxyUser, proxyPassword);
            return response.request()
                    .newBuilder()
                    .header("Proxy-Authorization", credential)
                    .build();
        };
    }
}

But request body has only 33 symbols. Content-Length = 33. How can I fix it?
The request body length greater then 33 letters

I try to add headers.add(HttpHeaders.CONTENT_LENGTH, contentLength);