How to use WebClient in SpringCloud gateway to asynchronously call a microservice?

2 years ago
Benjamin Taylor
2 minutes

To make asynchronous calls to microservices using WebClient in Spring Cloud Gateway, follow these steps:

  1. Add dependencies: include the dependencies for WebClient and Spring Cloud Gateway in the project’s pom.xml file.
<dependencies>
    <!-- Spring Cloud Gateway -->
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-gateway</artifactId>
    </dependency>

    <!-- WebClient -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-webflux</artifactId>
    </dependency>
</dependencies>
  1. Create a GatewayFilter: Create a GatewayFilter to handle requests and use WebClient to asynchronously call the microservice.
@Component
public class MyGatewayFilter implements GlobalFilter, Ordered {

    private final WebClient webClient;

    public MyGatewayFilter(WebClient.Builder webClientBuilder) {
        this.webClient = webClientBuilder.build();
    }

    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        // 异步调用微服务
        Mono<ClientResponse> responseMono = webClient.get()
                .uri("http://microservice/service")
                .exchange();

        // 处理响应
        return responseMono.flatMap(response -> {
            // 复制响应状态码、头部信息等
            ServerHttpResponse serverResponse = exchange.getResponse();
            serverResponse.setStatusCode(response.statusCode());
            serverResponse.getHeaders().putAll(response.headers().asHttpHeaders());

            // 转发响应体
            return response.bodyToMono(String.class)
                    .flatMap(body -> {
                        serverResponse.getHeaders().setContentLength(body.length());
                        return serverResponse.writeWith(Mono.just(serverResponse.bufferFactory().wrap(body.getBytes())));
                    });
        });
    }

    @Override
    public int getOrder() {
        return -1;
    }
}
  1. Configure a GatewayFilter: Set up the GatewayFilter in the application’s configuration file.
spring:
  cloud:
    gateway:
      routes:
        - id: my_route
          uri: http://localhost:8080/
          filters:
            - MyGatewayFilter

In this way, when routing with Spring Cloud Gateway, the MyGatewayFilter will be automatically invoked to handle the request and use WebClient to asynchronously call the microservices.

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