Spring WebClient set Bearer auth token in header

Question

Following scenario:

I have two Microservices A and B. Service A is a Bearer client that has an open api and receives requests from clients that have to be authorized by keycloak. Now I want to send an authorized Request from Service A to Service B, which is also a bearer client.

I thought about adding the functionality as a filter function during the webclient builder process like

@Bean
WebClient webClient() {
    return WebClient.builder()
            .filter(authHeader())
            .build();
}

private ExchangeFilterFunction authHeader(String token) {
    return (request, next) -> next.exchange(ClientRequest.from(request).headers((headers) -> {
        headers.setBearerAuth(token);
    }).build());
}

This is an example I found in another question. It seems to to be the right way to me but can I provide the "String token" parameter at that stage of configuration?

I'm just switching from RestTemplate to WebClient, so sorry I this is a dump question.

EDIT: I am able to set the header manually while building a new WebClient.

return WebClient.builder()
        .defaultHeader("Authorization", "Bearer "+ context.getTokenString())
        .build();

As I know from the RestTemplate, it can be used as a Singleton. There also exists a KeyCloakRestTemplate which injects the header automatically.

WebClient is immutable, so when I inject it, I can't just use it and add the header afterwards. In addition, I can't set this header on startup as I have to wait for a request to take the bearer header and pass it in. So I guess there is not other way than doing it this way?

It does not work for me if I set the bearer token as `default header`. I have to insert it as header when requesting. Any idea why? — Flimtix, Jun 02 '22 at 15:02

score 4 · Answer 1 · answered Feb 09 '22 at 08:38

4

Or simply set it during the process of sending:

webClient.get()
    .uri(url)
    .headers(h -> h.setBearerAuth(token))
    .retrieve();

answered Feb 09 '22 at 08:38

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score 2 · Answer 2 · answered Sep 08 '22 at 22:01

I ended up using an ExchangeFilterFunction filter in a similar situation. In my case, I have a Spring component which retrieves the token to use. If context in your context.getTokenString() example is a Spring bean, you should be able to do the same:

@Bean
WebClient webClient(SomeContext context) {
    return WebClient.builder()
            .filter((request, next) -> next.exchange(
                    withBearerAuth(request, context.getTokenValue())))
            .build();
}

private static ClientRequest withBearerAuth(ClientRequest request, 
                                            String token) {
    return ClientRequest.from(request)
            .header(HttpHeaders.AUTHORIZATION, "Bearer " + token)
            .build();
}

Spring WebClient set Bearer auth token in header

2 Answers2