如何使用Spring bootWebClient收集分页API响应？

Question

我有一个来自URL的分页响应，我想继续点击我从上一个响应中获得的下一页URL，并继续收集项目，直到我的响应中没有“nextPage”URL。如何使用WebFlux的Spring引导WebClient在没有阻塞的情况下以反应式方式实现这一点？

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
    }

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

如何在不阻塞的情况下，以被动方式从上述响应中提取所有项目？

Answer 1

您可以使用扩展来达到预期的效果：

@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;
    }
}

上述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

每个数据对象有两个UUID。

Answer 2

使用expand可以实现这一点。基于您提供的模拟URL。

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);
    }