Webclient passthru #webflux #webclient #springboot

WebclientPassthruApplication.java

package sandipchitale.webclient;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatusCode;
import org.springframework.http.ResponseEntity;
import org.springframework.http.client.reactive.ClientHttpRequest;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.reactive.function.BodyInserters;
import org.springframework.web.reactive.function.client.ClientRequest;
import org.springframework.web.reactive.function.client.ClientResponse;
import org.springframework.web.reactive.function.client.ExchangeFilterFunction;
import org.springframework.web.reactive.function.client.WebClient;
import reactor.core.publisher.Mono;
import reactor.netty.http.client.HttpClientRequest;

import java.time.Duration;

@SpringBootApplication
public class WebclientPassthruApplication {

	public static void main(String[] args) {
		SpringApplication.run(WebclientApplication.class, args);
	}

	@RestController
	public static class WebclientController {
		private final WebClient.Builder webClientBuilder;

		public WebclientController() {
			this.webClientBuilder = WebClient.builder()
					.baseUrl("https://postman-echo.com")
					.filter(getXTimeoutMillisFilter())
					.filter(getXFrameOptionsFilter());
		}

		/**
		 * If X-Timeout-Millis request header is present in the request then set the response timeout to that value.
		 * Remove cookie header.
		 *
		 * @return
		 */
		private static ExchangeFilterFunction getXTimeoutMillisFilter() {
			return ExchangeFilterFunction.ofRequestProcessor((ClientRequest clientRequest) -> {
				String timeoutMillis = clientRequest.headers().getFirst("X-Timeout-Millis");
				if (timeoutMillis != null) {
					return Mono.just(ClientRequest.from(clientRequest)
							.headers(httpHeaders -> {
								// Cleanup the header
								// httpHeaders.remove("X-Timeout-Millis");
								// sensitive headers
								httpHeaders.remove(HttpHeaders.COOKIE);
							})
							.httpRequest((ClientHttpRequest clientHttpRequest) -> {
								HttpClientRequest reactorRequest = clientHttpRequest.getNativeRequest();
								reactorRequest.responseTimeout(Duration.ofMillis(Long.parseLong(timeoutMillis)));
							})
							.build());
				}
				return Mono.just(clientRequest);
			});
		}

		/**
		 * Set X-Frame-Options response header to SAMEORIGIN.
		 *
		 * @return
		 */
		private static ExchangeFilterFunction getXFrameOptionsFilter() {
			return ExchangeFilterFunction.ofResponseProcessor((ClientResponse clientResponse) -> {
				clientResponse = clientResponse
						.mutate()
						.headers(httpHeaders -> {
							// Remove some headers
							// httpHeaders.remove(HttpHeaders.SET_COOKIE);
						})
						.header("X-Frame-Options", "SAMEORIGIN")
						.build();
				return Mono.just(clientResponse);
			});
		}

		@RequestMapping("/method")
		public Mono<ResponseEntity<byte[]>> method(ServerHttpRequest serverHttpRequest) {
			return webClientBuilder
					.build()
					.method(serverHttpRequest.getMethod())
					.uri("/" + serverHttpRequest.getMethod().name().toLowerCase())
					.headers(httpHeaders -> {
						httpHeaders.addAll(serverHttpRequest.getHeaders());
					})
					// Pass body through as is
					.body(BodyInserters.fromDataBuffers(serverHttpRequest.getBody()))
					.retrieve()
					// Pass error response through as is
					.onStatus((HttpStatusCode status) -> {
								return status.isError();
							},
							(ClientResponse clientResponse) -> {
								return Mono.empty();
							})
					// Pass response through as is
					.toEntity(byte[].class);
		}
    }
}