Clever Geek Handbook

Spring Boot WebClient Cheat Sheet

In anticipation of the start of the Spring Framework Developer course , we have prepared a traditional translation of useful material.



We also offer absolutely free of charge to watch a demo-lesson recording on the topic "Introduction to clouds, creating a cluster in Mongo DB Atlas" .









WebClient — , HTTP-.





RestTemplate

, , RestTemplate . :





NOTE: As of 5.0 this class is in maintenance mode, with only minor requests for changes and bugs to be accepted going forward. Please, consider using the org.springframework.web.reactive.client.WebClient



which has a more modern API and supports sync, async, and streaming scenarios.









: 5.0, . , org.springframework.web.reactive.client.WebClient



, API , .





, , RestTemplate , . , WebClient . . 





WebClient RestTemplate

, , RestTemplate (), WebClient ( ).





RestTemplate — HTTP-, API HTTP-, HttpURLConnection



(JDK), HttpComponents



(Apache) .





Spring WebClient — , HTTP-, Spring WebFlux.





, , , . WebClient . WebClient. 





RestTemplate , WebClient.





WebClient

  • Spring Boot 2





  • JDK 11





, Spring Initializr.





. —  spring-boot-starter-webflux



.





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

Spring WebFlux Spring 5 -.





WebClient.





WebClient

WebClient. — .





WebClient client = WebClient.create();

URL:





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

— WebClient . , URL .





@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();
    }
}

, WebClient.Builder .





Spring WebClient

WebClient : get()



, post()



, put()



, patch()



, delete()



, options()



head()



.





:





  • (path variables



    ) uri()



    .





  • headers()



    .





  • cookies()



    .





retrieve()



exchange()



. Mono bodyToMono()



Flux bodyToFlux()



.





, WebClient .





@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);
    }
}

, User. User Mono-, . , subscribe()



.





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

subscribe()



, .





, block()



.





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

, . .





, . . retryWhen()



, response.util.retry.Retry



.





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();
}

(, ). , repeatWhen()



repeatWhenEmpty()



retryWhen()



.





, , . :





  • doOnError()



    — , Mono .





  • onErrorResume()



    — , .





, , .





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();
}

. onStatus()



.





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 .





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();

, WebClient HTTP-. , , GitHub-. Spring WebClient .





, , WebClient , .





Spring WebClient!





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