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

Answer 1

You can use an ExchangeFilterFunction and configure it on the WebClient instance you’re using. See the Spring Framework reference documentation for more on that.

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);
            });
}

Answer 3

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);
    };
}