How to intercept a request when using SpringBoot WebClient

Question

I am trying to use the WebClient to call my restServices. Previously on RestTemplate, we had ClientHttpRequestInterceptor defined and attached to the RestTemplate to intercept and modify the requests. With the WebClient, is there a way to do the same ?

Thanks,

-Sreeni

Answer 1

When you are using the WebClient Builder you can pass in implementations of the ExchangeFilterFunction interface using the filter() method. This is the equivalent of the ClientHttpRequestInterceptor for RestTemplate.

WebClient Builder Docs: https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/web/reactive/function/client/WebClient.Builder.html#filter-org.springframework.web.reactive.function.client.ExchangeFilterFunction-

ExchangeFilterFunction Docs: https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/web/reactive/function/client/ExchangeFilterFunction.html

For example:

WebClient webClient = WebClient.builder()
        .baseUrl("http://localhost:8080|)
        .filter(logFilter())
        .build();


private ExchangeFilterFunction logFilter() {
    return (clientRequest, next) -> {
        logger.info("External Request to {}", clientRequest.url());
        return next.exchange(clientRequest);
    };
}

Answer 2

In my case i need to get Some headers from incoming requests and put them into my requests. I find what i need here.

First of all a filter is needed

/**
 * ReactiveRequestContextFilter
 *
 * @author L.cm
 */
@Configuration
@ConditionalOnWebApplication(type = ConditionalOnWebApplication.Type.REACTIVE)
public class ReactiveRequestContextFilter implements WebFilter {

    @Override
    public Mono<Void> filter(ServerWebExchange exchange, WebFilterChain chain) {
        ServerHttpRequest request = exchange.getRequest();
        return chain.filter(exchange)
        .subscriberContext(ctx -> ctx.put(ReactiveRequestContextHolder.CONTEXT_KEY, request));
    }
}

And ReactiveRequestContextHolder

/**
 * ReactiveRequestContextHolder
 *
 * @author L.cm
 */
public class ReactiveRequestContextHolder {
    static final Class<ServerHttpRequest> CONTEXT_KEY = ServerHttpRequest.class;

    /**
     * Gets the {@code Mono<ServerHttpRequest>} from Reactor {@link Context}
     * @return the {@code Mono<ServerHttpRequest>}
     */
    public static Mono<ServerHttpRequest> getRequest() {
        return Mono.subscriberContext()
            .map(ctx -> ctx.get(CONTEXT_KEY));
    }

}

And finally like Michael McFadyen say you need to configure an ExchangeFilterFunction, in my case i need Auth and origin:

private ExchangeFilterFunction headerFilter() {
    return (request, next) -> ReactiveRequestContextHolder.getRequest()
            .flatMap(r -> {
                ClientRequest clientRequest = ClientRequest.from(request)
                        .headers(headers -> {
                            headers.set(HttpHeaders.ORIGIN, r.getHeaders().getFirst(HttpHeaders.ORIGIN));
                            headers.set(HttpHeaders.AUTHORIZATION, r.getHeaders().getFirst(HttpHeaders.AUTHORIZATION));
                        })
                        .build();
                return next.exchange(clientRequest);
            });
}