如何使用 spring 引导 WebClient 收集分页的 API 响应？

Question

我有一个 URL 的分页回复，我想继续点击下一页 URL 我从上一个回复中得到并继续收集项目直到我没有a "nextPage" URL 在我的回复中。如何使用 spring 从 WebFlux 引导 WebClient 以无阻塞的方式以反应方式实现这一点？

Request1: 

    GET /items
    response: 
    {
        items: [...]
        nextPage: "/items?page=2"
    }


    Request2: 

    GET /items?page=2
    response: 
    {
        items: [...]
        nextPage: "/items?page=3"
    }


    Request3: 

    GET /items?page=3
    response: 
    {
        items: [...]
        nextPage: null
    }

我在这里创建了模拟网址 https://karthikdivi.com/apps/paginatedReviews/withNextPageTokens/items https://karthikdivi.com/apps/paginatedReviews/withNextPageTokens/items?page=2 https://karthikdivi.com/apps/paginatedReviews/withNextPageTokens/items?page=3

如何在不阻塞的情况下以反应方式从上述响应中提取所有项目？

Answer 1

你可以使用expand达到你想要的效果：

@Test
public void usingExpand(){

    Request innerData = new Request(null);
    Request middleData = new Request(innerData);
    Request rootData = new Request(middleData);

    Mono.just(rootData)
            .expand( t -> Mono.justOrEmpty(t.nextPage))
            .flatMap( t -> Flux.fromIterable(t.items))
            .subscribe(System.out::println);

}

public static class Request {
    List<String> items = new ArrayList<>();
    Request nextPage;

    public Request(Request nextPage) {
        this.items.add(UUID.randomUUID().toString());
        this.items.add(UUID.randomUUID().toString());
        this.nextPage = nextPage;
    }
}

以上代码应产生以下结果：

dc78317c-5552-4723-90db-5392c67655be
32ff12bb-5be1-415e-b481-dab85d9157dd
cf1e3f36-a8e2-414d-90a2-7708eeedc5be
91a6bc14-a396-483d-a66a-80bb98dc1968
c95adae3-8e6f-489b-8a9d-4cea3080e150
d6f8fe01-2c50-4574-958c-ec675331bb25

每个数据对象的两个 UUID。

Answer 2

使用expand可以实现。根据您提供的模拟网址。

public Mono<List<Item>> getItems() {
    String url = "https://karthikdivi.com/apps/paginatedReviews/withNextPageTokens/items";

    return fetchItems(url).expand(response -> {
        if (response.getNextPage() == null) {
            return Mono.empty();
        }
        return fetchItems(response.getNextPage());
    }).flatMap(response -> Flux.fromIterable(response.getItems())).collectList();
}

private Mono<Response> fetchItems(String url) {

         return client.get().uri(url).retrieve()
                    .bodyToMono(Response.class);
    }

如何使用 spring 引导 WebClient 收集分页的 API 响应？

How to collect paginated API responses using spring boot WebClient?

spring

reactive-programming

spring-boot

project-reactor

spring-webflux