Spring WebClient : Call method in retry

Question

I have been looking for a solution to the following use case without success, I hope someone can help :

Assuming the following use case. I need to call a customer Api (customerApi) and this api needs a Bearer token which may have expired when I call customerApi. If the token has expired, the customerApi returns a 401 response.

What, I want to do is to retry only once if I received a 401 and call the method to get a new Bearer token. If the retry still returns 401, I need to throw an Exception

The method to get a Bearer token :

private String getToken() {
    return oAuthService.getToken();
}

And the webClient usage to call customerApi (customerWebClient is a bean created with WebClient.Builder) :

public Customer getCustomerById(String customerId, String token) {
        return customerWebClient.get()
            .uri("myurl/customers/{customerId}, customerId)
            .headers(httpHeaders -> {
                httpHeaders.add(HttpHeaders.AUTHORIZATION, "Bearer " + token);
            })
            .retrieve()
            .bodyToMono(Customer.class)
            .onErrorResume(WebClientResponseException.NotFound.class, notFound ->
                        Mono.error(new MyCustomException()))
            .block();
    }

It seems that retryWhen can only be used to upgrade timeout. So I hope that someone know how to achieve this use case ^^

Thanks for your help :)

EDIT :

I tried to use retryWhen(Retry.onlyIf(...)) from reactor-extra but the good old retryWhen from this package is now deprecated (solution based on : Adding a retry all requests of WebClient)

Answer 1

The method

public final Mono<T> retryWhen(Function<Flux<Throwable>, ? extends Publisher<?>> whenFactory)

has been deprecated and now the preferred method is

public final Mono<T> retryWhen(Retry retrySpec)

So, you can modify your code to something like this to make it work with the new retryWhen

public Customer getCustomerById(String customerId, String token) {

    HttpHeaders headers = new HttpHeaders();
    headers.add(HttpHeaders.AUTHORIZATION, "Bearer " + token);

    final RetrySpec retrySpec = Retry.max(1).doBeforeRetry(
        retrySignal -> headers.add(HttpHeaders.AUTHORIZATION, "Bearer " + someTokenGetterMethod()))
        .filter(throwable -> throwable.getClass() == Unauthorized.class);

    return Mono.defer(() -> webClient.get().uri("myurl/customers/{customerId}, customerId")
        .headers(httpHeaders -> httpHeaders.addAll(headers))
        .retrieve()
        .bodyToMono(Customer.class))
        .retryWhen(retrySpec)
        .onErrorResume(WebClientResponseException.NotFound.class,
            notFound -> Mono.error(new MyCustomException()))
        .block();
}

Here's a working example using https://httpbin.org/

public CommandLineRunner commandLineRunner() {

    HttpHeaders headers = new HttpHeaders();

    final RetrySpec retrySpec = Retry.max(1).doBeforeRetry(
        retrySignal -> headers.add("Authorization", "Bearer 1234")).filter(
        throwable -> throwable.getClass() == Unauthorized.class);

    return args -> Mono.defer(() -> webClient.get().uri("https://httpbin.org/bearer")
        .headers(httpHeaders -> httpHeaders.addAll(headers)).retrieve().toEntity(Map.class)
        .retryWhen(retrySpec)
        .subscribe(objectResponseEntity -> System.out
            .println("objectResponseEntity = " + objectResponseEntity.getBody()));
}

Also, I do not think the way you're trying to manipulate headers in retry to add authorization token is the right way of achieving this. You must come up with a better solution/design.