java - Project Reactor如何并行调用两个或多个web服务或REST并加入答案

Question

您好，我想知道如何在 pararelo 中调用两个或多个 Web 服务或 Rest 服务，并编写调用响应。

我在网上找到了一些使用其他技术的例子，但我无法让它与 react 堆一起工作

// start task A asynchronously
CompletableFuture<ResponseA> futureA = asyncServiceA.someMethod(someParam);
// start task B asynchronously
CompletableFuture<ResponseB> futureB = asyncServiceB.someMethod(someParam);

CompletableFuture<String> combinedFuture = futureA
        .thenCombine(futureB, (a, b) -> a.toString() + b.toString());

// wait till both A and B complete
String finalValue = combinedFuture.join();

////////////////////////////////////////////////////////////////////////////

static void Run()
{
    //Follow steps at this link for addding a reference to the necessary .NET library:
    //http://stackoverflow.com/questions/9611316/system-net-http-missing-from-    
    //namespace-using-net-4-5

    //Create an HTTP Client
    var client = new HttpClient();

    //Call first service
    var task1 = client.GetAsync("http://www.cnn.com");

    //Call second service
    var task2 = client.GetAsync("http://www.google.com");

    //Create list of all returned async tasks
    var allTasks = new List<Task<HttpResponseMessage>> { task1, task2 };

    //Wait for all calls to return before proceeding
    Task.WaitAll(allTasks.ToArray());

}

Answer 1

假设您需要访问 2 个服务，所以您需要 2 个基础 WebClient (每个都配置了正确的基本 URL 和身份验证方案):

@Bean
public WebClient serviceAClient(String authToken) {
    return WebClient.builder()
            .baseUrl("http://serviceA.com/api/v2/")
            .defaultHeader(HttpHeaders.AUTHORIZATION, "Basic " + authToken)
            .defaultHeader(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE)
            .build();
}

@Bean
public WebClient serviceBClient(String authToken): WebClient {
    return WebClient.builder()
            .baseUrl("https://api.serviceB.com/")
            .defaultHeader(HttpHeaders.AUTHORIZATION, "token " + authToken)
            .defaultHeader(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE)
            .build();
}

从那里开始，假设您将这 2 个 Web 客户端注入(inject)到您的 Controller 中(作为 合格 bean)。下面是使用 Reactor 对两者进行联合调用的代码:

Mono<ResponseA> respA = webclientA.get()
                                 .uri("/sub/path/" + foo)
                                 .retrieve()
                                 .bodyToMono(ResponseA.class);
Mono<ResponseB> respB = webclientB.get()
                                 .uri("/path/for/b")
                                 .retrieve()
                                 .bodyToMono(ResponseB.class);
Mono<String> join = respA.zipWith(respB, (a, b) -> a.toString + b.toString);
return join;

请注意，zip 函数可以从 2 个响应中生成更有意义的内容，例如业务对象。结果 Mono<String>仅当有内容订阅时触发 2 个请求(在 Spring WebFlux 的情况下，如果您从 Controller 方法返回它，框架将执行此操作)。