如何在Spring Cloud Gateway过滤器中将WebClient响应转为ServerHttpResponse？

核心实现思路 #

当请求头包含Test时，通过WebClient调用目标服务，将目标服务的响应（状态码、响应头、响应体）直接作为网关的响应返回，不再继续执行后续过滤器链。

完整代码实现 #

import org.springframework.cloud.gateway.filter.GatewayFilter;
import org.springframework.cloud.gateway.filter.GatewayFilterChain;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.client.reactive.ClientHttpResponse;
import org.springframework.stereotype.Component;
import org.springframework.web.reactive.function.client.WebClient;
import org.springframework.web.server.ServerWebExchange;
import reactor.core.publisher.Mono;

@Component
public class CustomForwardFilter implements GatewayFilter {

    private final WebClient webClient;

    // 推荐通过构造注入WebClient，避免每次创建新实例
    public CustomForwardFilter(WebClient.Builder webClientBuilder) {
        this.webClient = webClientBuilder.build();
    }

    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        if (exchange.getRequest().getHeaders().containsKey("Test")) {
            ServerHttpResponse response = exchange.getResponse();
            String targetUrl = "http://localhost:8080/test";

            return webClient.get()
                    .uri(targetUrl)
                    .exchangeToMono(clientResponse -> {
                        // 复制目标服务的响应状态码
                        response.setStatusCode(clientResponse.statusCode());
                        // 复制目标服务的响应头（排除Transfer-Encoding等网关会处理的头）
                        HttpHeaders targetHeaders = clientResponse.headers().asHttpHeaders();
                        response.getHeaders().putAll(targetHeaders);
                        // 写入响应体到网关响应
                        return response.writeWith(clientResponse.bodyToFlux(byte[].class));
                    });
        }
        // 不满足条件时继续执行过滤器链
        return chain.filter(exchange);
    }
}

关键细节说明 #

• WebClient实例管理：不要每次调用都用WebClient.create()创建新实例，推荐通过WebClient.Builder注入，实现复用和统一配置。
• 响应头处理：复制目标服务的响应头时，网关会自动处理Transfer-Encoding、Content-Length等头，无需手动干预。
• 响应体写入：使用bodyToFlux(byte[].class)将目标服务的响应体转为Flux，再通过response.writeWith()写入到网关响应中，保证响应体完整传输。
• 异常处理（可选）：如果需要处理目标服务调用失败的情况，可以添加onErrorResume逻辑，比如返回自定义错误响应：

  .onErrorResume(e -> {
      response.setStatusCode(HttpStatus.INTERNAL_SERVER_ERROR);
      response.getHeaders().setContentType(MediaType.TEXT_PLAIN);
      String errorMsg = "调用目标服务失败: " + e.getMessage();
      return response.writeWith(Mono.just(response.bufferFactory().wrap(errorMsg.getBytes())));
  })
  

内容的提问来源于stack exchange，提问作者LucyEly