AbstractWebClient.java

public abstract class AbstractWebClient {
    private static final String MIME_TYPE = "application/json";
    private final WebClient webClient;

    public AbstractWebClient(String clientUrl) {

        this.webClient = WebClient.builder()
                .baseUrl(clientUrl)
                .defaultHeader(HttpHeaders.CONTENT_TYPE, MIME_TYPE)
                .build();
    }

    public <T> Mono<T> get(String uri, Class<T> tClass) {

        return webClient.get()
                .uri(uri)
                .header("X-B3-TRACEID", MDC.get("X-B3-TraceId"))
                .retrieve()
                .onStatus(HttpStatus::is4xxClientError, this::get4xxError)
                .onStatus(HttpStatus::is5xxServerError, this::get5xxError)
                .bodyToMono(tClass);
    }

    public <T> Mono<T> post(String uri, Object body, Class<T> tClass) {

        return webClient.post()
                .uri(uri)
                .header("X-B3-TRACEID", MDC.get("X-B3-TraceId"))
                .syncBody(body)
                .retrieve()
                .onStatus(HttpStatus::is4xxClientError, this::get4xxError)
                .onStatus(HttpStatus::is5xxServerError, this::get5xxError)
                .bodyToMono(tClass);
    }

    private <T> Mono<T> get4xxError(ClientResponse clientResponse) {

        return Mono.error(new Client4xxException("Client Error"));
    }

    private <T> Mono<T> get5xxError(ClientResponse clientResponse) {

        return Mono.error(new Client5xxException("Server Error"));
    }

}