<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-webflux</artifactId>
</dependency>

WebClient client = WebClient.create();

WebClient client = WebClient.create("http://base-url.com");

@Configuration
public class WebClientConfiguration {
    private static final String BASE_URL = "https://jsonplaceholder.typicode.com";
    public static final int TIMEOUT = 1000;
    @Bean
    public WebClient webClientWithTimeout() {
        final var tcpClient = TcpClient
                .create()
                .option(ChannelOption.CONNECT_TIMEOUT_MILLIS, TIMEOUT)
                .doOnConnected(connection -> {
                    connection.addHandlerLast(new ReadTimeoutHandler(TIMEOUT, TimeUnit.MILLISECONDS));
                    connection.addHandlerLast(new WriteTimeoutHandler(TIMEOUT, TimeUnit.MILLISECONDS));
                });
        return WebClient.builder()
                .baseUrl(BASE_URL)
                .clientConnector(new ReactorClientHttpConnector(HttpClient.from(tcpClient)))
                .build();
    }
}

@Service
@AllArgsConstructor
public class UserService {
    private final WebClient webClient;
    public Mono<User> getUserByIdAsync(final String id) {
        return webClient
                .get()
                .uri(String.join("", "/users/", id))
                .retrieve()
                .bodyToMono(User.class);
    }
}

userService
  .getUserByIdAsync("1")
  .subscribe(user -> log.info("Get user async: {}", user));

public User getUserByIdSync(final String id) {
    return webClient
            .get()
            .uri(String.join("", "/users/", id))
            .retrieve()
            .bodyToMono(User.class)
            .block();
}

public User getUserWithRetry(final String id) {
    return webClient
            .get()
            .uri(String.join("", "/users/", id))
            .retrieve()
            .bodyToMono(User.class)
            .retryWhen(Retry.fixedDelay(3, Duration.ofMillis(100)))
            .block();
}

public User getUserWithFallback(final String id) {
    return webClient
            .get()
            .uri(String.join("", "/broken-url/", id))
            .retrieve()
            .bodyToMono(User.class)
            .doOnError(error -> log.error("An error has occurred {}", error.getMessage()))
            .onErrorResume(error -> Mono.just(new User()))
            .block();
}

public User getUserWithErrorHandling(final String id) {
  return webClient
          .get()
          .uri(String.join("", "/broken-url/", id))
          .retrieve()
              .onStatus(HttpStatus::is4xxClientError,
                      error -> Mono.error(new RuntimeException("API not found")))
              .onStatus(HttpStatus::is5xxServerError,
                      error -> Mono.error(new RuntimeException("Server is not responding")))
          .bodyToMono(User.class)
          .block();
}

WebClient.builder()
  .baseUrl(BASE_URL)
  .filter((request, next) -> next
          .exchange(ClientRequest.from(request)
                  .header("foo", "bar")
                  .build()))
  .clientConnector(new ReactorClientHttpConnector(HttpClient.from(tcpClient)))
  .build();

WebClient.builder()
  .baseUrl(BASE_URL)
  .filter(basicAuthentication("user", "password")) // org.springframework.web.reactive.function.client.basicAuthentication()
  .clientConnector(new ReactorClientHttpConnector(HttpClient.from(tcpClient)))
  .build();