CODEWITHSUNDEEP
spring-bootspring-webflux
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Reputation: 18859

How to handle exceptions thrown by the webclient?

I'm trying to figure out how to log exceptions from the webclient, whatever the error status code that is returned from the api that gets called.

I've seen the following implementation: 

.onStatus(status -> status.value() != HttpStatus.OK.value(),
            rs -> rs.bodyToMono(String.class).map(body -> new IOException(String.format(
                "Response HTTP code is different from 200: %s, body: '%s'", rs.statusCode(), body))))

Another example I've seen uses a filter. I guess this filter could be used to log errors as well, aside from requests like in this example: 

public MyClient(WebClient.Builder webClientBuilder) {
    webClient = webClientBuilder // you can also just use WebClient.builder()
            .baseUrl("https://httpbin.org")
            .filter(logRequest()) // here is the magic
            .build();
}

But are we serious that there is no dedicated exception handler to this thing?

Upvotes: 7

Views: 10088

Answers (1)

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Reputation: 18859

Found it.
bodyToMono throws a WebClientException if the status code is 4xx (client error) or 5xx (Server error).

Full implementation of the service: 

@Service
public class FacebookService {
    private static final Logger LOG = LoggerFactory.getLogger(FacebookService.class);
    private static final String URL_DEBUG = "https://graph.facebook.com/debug_token";
    private WebClient webClient;

    public FacebookService() {
        webClient = WebClient.builder()
                .filter(logRequest())
                .build();
    }

    public Mono<DebugTokenResponse> verifyFbAccessToken(String fbAccessToken, String fbAppToken) {
        LOG.info("verifyFacebookToken for " + String.format("fbAccessToken: %s and fbAppToken: %s", fbAccessToken, fbAppToken));
        UriComponentsBuilder builder = UriComponentsBuilder.fromHttpUrl(URL_DEBUG)
                .queryParam("input_token", fbAccessToken)
                .queryParam("access_token", fbAppToken);
        return this.webClient.get()
                .uri(builder.toUriString())
                .retrieve()
                .bodyToMono(DebugTokenResponse.class);
    }

    private static ExchangeFilterFunction logRequest() {
        return ExchangeFilterFunction.ofRequestProcessor(clientRequest -> {
            LOG.info("Request: {} {}", clientRequest.method(), clientRequest.url());
            clientRequest.headers().forEach((name, values) -> values.forEach(value -> LOG.info("{}={}", name, value)));
            return Mono.just(clientRequest);
        });
    }

    @ExceptionHandler(WebClientResponseException.class)
    public ResponseEntity<String> handleWebClientResponseException(WebClientResponseException ex) {
        LOG.error("Error from WebClient - Status {}, Body {}", ex.getRawStatusCode(), ex.getResponseBodyAsString(), ex);
        return ResponseEntity.status(ex.getRawStatusCode()).body(ex.getResponseBodyAsString());
    }
}

Upvotes: 4

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