Issue with Spring Webflux webclient , nothing happens when trying to send post request

Question

Have the following implementation of webclient :

    public <T> WebClient.ResponseSpec sendRequest(HttpMethod method, String contentType, T body, String baseUrl, String path) {
    try {
        WebClient webClient = WebClient.builder().baseUrl(baseUrl).filter(logRequest()).build();
        WebClient.ResponseSpec responseSpec = webClient.method(method)
                .uri(path)
                .header(HttpHeaders.CONTENT_TYPE, contentType)
                .body(BodyInserters.fromObject(body))
                .retrieve();
        return responseSpec;
    } catch (Exception e) {
        throw new WebClientProcessingException("Exception when trying to execute request", e);

    }
}

// This method returns filter function which will log request data
private static ExchangeFilterFunction logRequest() {
    return ExchangeFilterFunction.ofRequestProcessor(clientRequest -> {
        LOGGER.info("Request: {} {} {}", clientRequest.method(), clientRequest.url(), clientRequest.body());
        clientRequest.headers().forEach((name, values) -> values.forEach(value -> LOGGER.info("{}={}", name, value)));
        return Mono.just(clientRequest);
    });
}

Also have the following code , which is creating user object and command which contains user object , then calling webclient to send an request

@Autowired
private BaseWebClient baseWebClient;
@Override
public void saveOrUpdateUser() {
        UserPayload userPayload = new UserPayload();
        userPayload.setUserId(111L);
        userPayload.setCreatedAt(ZonedDateTime.now(DateTimeProps.systemTimeZone));
        UserCommand userCommand = new UserCommand();
        userCommand.setUser(userPayload);
        baseWebClient.sendRequest(HttpMethod.POST, "application/json",
            Stream.of(userCommand).collect(Collectors.toList()),
            "http://localhost:8080",
            "/users").onStatus(HttpStatus::isError, clientResponse -> {
        throw new WebClientUserSaveOrUpdateeFailedException("Exception when trying to update user state")
        .bodyToMono(String.class);
    });
}

User payload :

@Data
@NoArgsConstructor
@AllArgsConstructor
public class UserPayload {
  Long userId;
  ZonedDateTime createdAt;
}

User command :

@Data
@NoArgsConstructor
@AllArgsConstructor
public class UserCommand {
     @JsonProperty("user")
     UserPayload user;
}

Json which is waiting for my other app (whom I am sending a request) :

[
  { "user":
            { 
              "userId": 1,
              "createdAt": "2019-05-16T08:24:46.412Z"
            } 
  }
]

Using : Spring boot 2 , Lombok (for getter/setter) , gradle When I'm trying to send a request nothing happens. No exception even. I tried with very simple case as well the same issue. One more note, is it possible to log body? I mean somehow see final json I guess I am missing something general.

Answer 1

In Reactor, nothing happens until you subscribe. retrive() does not actually start the request. As you can see in the example, you should use one of the method to convert the ResponseSpec to a Publisher and then eventually subscribe to that publisher.

Depending on how you're using this method, you might be able to let Spring subscribe to the publisher instead. WebFlux supports reactive types in the model which means you can directly return a Mono from your RestController methods, for example.