SpringWebFlux WebClient Mono Dönüşümü

Giriş

WebClient cevabını Mono'ya dönüştürmek için yöntemler şöyle

1. bodyToMono

Örnek

Şöyle yaparız

WebClient webClient = WebClient.create();
Mono<String> responseOne = webClient.get()
    .uri("http://example.com/endpointOne")
    .retrieve()
    .bodyToMono(String.class);

Mono<String> responseTwo = webClient.get()
    .uri("http://example.com/endpointTwo")
    .retrieve()
    .bodyToMono(String.class);

// Use Mono.zip to execute requests concurrently
Mono.zip(responseOne, responseTwo).subscribe(results -> {
    System.out.println("Result 1: " + results.getT1());
    System.out.println("Result 2: " + results.getT2());
});

2. exchangeToMono Yöntemi

Örnek

Şöyle yaparız

WebClient webClient = WebClient.create();
Mono<String> getHttpNonBlocking(String url) {
    return webClient
            .get()
            .uri(url)
            .exchangeToMono(cr -> cr.bodyToMono(String.class));
}

3. exchange + flatmap Yöntemi

Örnek

Elimizde şöyle bir kod olsun. Bu kod hem Mono hem de Flux dönebiliyor. Hem get() hem de put() işlemi için exchange() çağrısı yapıyor. Kod bir  spring bean. İskeleti şöyle

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

@Component
public class WebClientHelper {

  private WebClient webClient;

  public WebClientHelper() {
    webClient = WebClient.create();
  }
}

Get ve Post için Mono dönen metodlar şöyle

public <T> Mono<T> performGetToMono(URI uri, MultiValueMap<String, String> params,
  Class<? extends T> clazzResponse){
    return webClient.get()
        .uri(uriBuilder -> uriBuilder.scheme(uri.getScheme()).host(uri.getHost())
            .port(uri.getPort()).path(uri.getPath()).queryParams(params).build()
        )
        .exchange()
        .flatMap(clientResponse -> clientResponse.bodyToMono(clazzResponse));
}
public <T> Mono<T> performPostToMono(URI uri, Object requestBody,
  Class<? extends T> clazzResponse){
    return webClient.post()
        .uri(uriBuilder -> uriBuilder.scheme(uri.getScheme()).host(uri.getHost())
            .port(uri.getPort()).path(uri.getPath()).build()
        )
        .body(BodyInserters.fromValue(requestBody))
        .exchange()
        .flatMap(clientResponse -> clientResponse.bodyToMono(clazzResponse));
}

Put ve Delete için Mono dönen metodlar şöyle

public <T> Mono<T> performPutToMono(URI uri, Object requestBody,
  Class<? extends T> clazzResponse){
    return webClient.put()
        .uri(uriBuilder -> uriBuilder.scheme(uri.getScheme()).host(uri.getHost())
            .port(uri.getPort()).path(uri.getPath()).build()
        )
        .body(BodyInserters.fromValue(requestBody))
        .exchange()
        .flatMap(clientResponse -> clientResponse.bodyToMono(clazzResponse));
}
public <T> Mono<T> performDeleteToMono(URI uri, MultiValueMap<String, String> params,
  Class<? extends T> clazzResponse){
    return webClient.delete()
        .uri(uriBuilder -> uriBuilder.scheme(uri.getScheme()).host(uri.getHost())
            .port(uri.getPort()).path(uri.getPath()).queryParams(params).build()
        )
        .exchange()
        .flatMap(clientResponse -> clientResponse.bodyToMono(clazzResponse));
}

Bu kodu kullanmak için şöyle yaparız

@RestController
@RequestMapping("/employeeClient")
public class EmployeeClientController {

  @Value("${employee.server.host}")
  private String employeeHost;

  @Autowired
  private WebClientHelper webClientHelper;

  @GetMapping("/{employeeId}")
  public Mono<EmployeeModel> getEmployeeById(@PathVariable("employeeId")
    String employeeId){
    String url = ApiPaths.getEmployeePath(employeeHost) + "/" + employeeId;
    return webClientHelper.performGetToMono(URI.create(url), null, EmployeeModel.class);
  }
 
  @PostMapping
  public Mono<EmployeeModel> saveEmployee(@RequestBody EmployeeModel employeeModel){
    return webClientHelper.performPostToMono(URI.create(ApiPaths.getEmployeePath(
      employeeHost)), employeeModel,
        EmployeeModel.class);
  }
  ...
}

Update ve Delete için şöyle yaparız

@PutMapping
public Mono<EmployeeModel> updateEmployee(@RequestBody EmployeeModel employeeModel){
  return webClientHelper
    .performPutToMono(URI.create(ApiPaths.getEmployeePath(employeeHost)), employeeModel,
      EmployeeModel.class);
  }
@DeleteMapping("/{id}")
public Mono<EmployeeModel> deleteEmployee(@PathVariable("id") Long employeeId){
  String url = ApiPaths.getEmployeePath(employeeHost) + "/" + employeeId;
  return webClientHelper.performDeleteToMono(URI.create(url),null, EmployeeModel.class);
}