SpringWebFlux WebClient.Builder Arayüzü

Giriş

Şu satırı dahil ederiz

import org.springframework.web.reactive.function.client.WebClient;

Kullanım

baseUrl()

defaultHeader()

metodları ile değerler atanır. En son olarak ta build() ile bir WebClient nesnesi elde edilir.

Örnek - Generic Kod

Elimizde şöyle bir kod olsun

@Data
@JsonInclude(JsonInclude.Include.NON_NULL)
public class GenericResponse<T> {
    private T responseEntity;
    private GenericError genericError;
}

Genel kullanım için yaparız. Burada WebClient.Builder enjekte ediliyor. Daha sonra build() çağrısı ile bir WebClient elde ediliyor. Ve WebClient ile HTTP işlemi yapılıyor.

private final WebClient.Builder webClientBuilder;


@Autowired
public GenericWebClient(WebClient.Builder webClientBuilder) {
  this.webClientBuilder = webClientBuilder;
}

@Retryable(
  value = {HttpServerErrorException.class, WebClientRequestException.class,
    WebClientResponseException.class},
  maxAttemptsExpression = "${generic.webclient.endpoint.maxAttempts:4}",
  backoff = @Backoff(delayExpression = "${generic.webclient.endpoint.maxDelay:4000}"))
public <T> ResponseEntity<GenericResponse<T>> execute(
  GenericRequest genericRequest, Object requestEntity) 
throws HttpServerErrorException, WebClientRequestException, WebClientResponseException {

  Mono<GenericResponse<T>> response = null;
  AtomicInteger cnt = new AtomicInteger(1);
  try {
    response = this.webClientBuilder.build()
      .method(genericRequest.getHttpMethod())
      .uri(genericRequest.getServiceUrl())
      .bodyValue(requestEntity)
      .retrieve()
      .bodyToMono(new ParameterizedTypeReference<GenericResponse<T>>() {
    })
    .doOnNext(apiResponse -> process(genericRequest.getServiceUrl(), apiResponse));
  } catch (HttpServerErrorException exception) {
    this.handleHttpServerErrorException(exception);
  } catch (WebClientRequestException exception) {
    if (exception.getCause() instanceof ConnectException) {
      log.error("Retry method called - {}", cnt.getAndIncrement());
      log.error("...", exception);
      throw exception;
    }
  } catch (WebClientResponseException exception) {
    if (exception.getStatusCode().is5xxServerError()) {
      log.error("...", exception);
      throw exception;
  }
}

baseUrl metodu

Örnek

Şöyle yaparız

@Value("${rest.UserDetailsService.service.endpoint}")
private String baseUrl;

private WebClient webClient;

@PostConstruct
private void init(){
  this.webClient = WebClient.builder().baseUrl(baseUrl).build();
}

clientConnector metodu

Örnek - ReactorClientHttpConnector

Şöyle yaparız. ReactorClientHttpConnector içine bir tane HttpClient nesnesi alır

import org.springframework.http.client.reactive.ReactorClientHttpConnector;
import org.springframework.web.reactive.function.client.WebClient;
import reactor.netty.http.client.HttpClient;

@Configuration
public class WebClientConfig {

  @Bean
  public WebClient webClient() {
    return WebClient.builder()
      .clientConnector(new ReactorClientHttpConnector(getHttpClient()))
      .baseUrl("<service-url>")
      .defaultHeader(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE)
      .build();
  }

  private HttpClient getHttpClient() {
    return HttpClient.create()
      .option(ChannelOption.CONNECT_TIMEOUT_MILLIS, 10_000)
      .doOnConnected(conn -> conn
        .addHandlerLast(new ReadTimeoutHandler(10))
        .addHandlerLast(new WriteTimeoutHandler(10)));
  }
}

Örnek - ReactorClientHttpConnector

Şöyle yaparız. ReactorClientHttpConnector içine bir tane HttpClient nesnesi alır

// Build a custom WebClient with specified timeout and default headers
WebClient customWebClient = WebClient.builder()
  .baseUrl("http://example.com")
  .clientConnector(new ReactorClientHttpConnector(
    HttpClient.create()
      .option(ChannelOption.CONNECT_TIMEOUT_MILLIS, 2000) // 2 seconds timeout
      .responseTimeout(Duration.ofSeconds(2)) // Set response timeout
      .doOnConnected(conn -> 
        conn.addHandlerLast(new ReadTimeoutHandler(2)) // 2 seconds read timeout
        .addHandlerLast(new WriteTimeoutHandler(2))))) // 2 seconds write timeout
   // Default header
  .defaultHeader(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE)
  .defaultHeader("Another-Header", "Another-Value") // Another default header
  .build();

Örnek - Mutual TLS

Şöyle yaparız. ReactorClientHttpConnector içine bir tane HttpClient nesnesi alır

// Preparing the SSL context with both trust store and key store
SslContext sslContext = SslContextBuilder
  .forClient()
  // for demo purposes only!
  .trustManager(InsecureTrustManagerFactory.INSTANCE) 
  // client certificate and private key
  .keyManager(new File("path/to/client.crt"), new File("path/to/client.key")) 
  .build();

// Configuring the WebClient with the SSL context
WebClient secureWebClient = WebClient.builder()
  .clientConnector(new ReactorClientHttpConnector(HttpClient.create()
    .secure(sslContextSpec -> sslContextSpec.sslContext(sslContext))))
    .build();

codecs metodu

Bir örnek burada

defaultHeader metodu

Örnek

Şöyle yaparız

public InventoryClient(InventoryClientProperties inventoryClientProperties) {
  HttpClient httpClient = HttpClient.create()
    .option(ChannelOption.CONNECT_TIMEOUT_MILLIS, 10000)
    .doOnConnected(conn -> conn
      .addHandlerLast(new ReadTimeoutHandler(10))
      .addHandlerLast(new WriteTimeoutHandler(10)));

  retrySpec = Retry
    .backoff(inventoryClientProperties.getRetry().getMaxAttempts(),
      inventoryClientProperties.getRetry().getBackoffDuration())
    .filter(throwable -> throwable instanceof ExternalCommunicationException)
    .onRetryExhaustedThrow(this::handleRetryExhaustedError);

  webClient = WebClient.builder()
    .baseUrl(inventoryClientProperties.getUrl() + "/books")
    .defaultHeader(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE)
    .clientConnector(new ReactorClientHttpConnector(httpClient))
    .build();
}

ServiceUnavailableException handleRetryExhaustedError(RetryBackoffSpec retryBackoffSpec,
                                                      RetrySignal retrySignal) {
  throw new ServiceUnavailableException("communication failed after max retries");
}

filter metodu

Açıklaması şöyle

WebClient supports the use of filters for cross-cutting concerns. These filters can be used to manipulate the request or response, or even to handle concerns like logging, metrics, or authorization.

Örnek

Şöyle yaparız.

WebClient.builder().baseUrl("/").filter(contentTypeInterceptor()).build();

Örnek - ReactorClientHttpConnector

Şöyle yaparız. ReactorClientHttpConnector içine bir tane HttpClient nesnesi alır

// Custom WebClient with a filter
WebClient filteredWebClient = WebClient.builder()
  .baseUrl("http://example.com")
  .filter((request, next) -> {
    // Log request data
    System.out.println("Request: " + request.method() + " " + request.url());
    return next.exchange(request).doOnSuccessOrError((response, error) -> {
      if (response != null) {
        // Log response data
        System.out.println("Response Status: " + response.statusCode());
      }
      if (error != null) {
        // Log error
        System.out.println("Error: " + error.getMessage());
      }
    });
})
.build();

Açıklaması şöyle

This filter logs the HTTP method and URL for every request made through this WebClient instance, and the status code for every response received. It also logs any error that might occur during the exchange.