How to use Reactor (Spring WebClient) to do a repeat call?

Question

I am using Reactor (Spring5 WebClient) as my reactive programming API. I have 2 REST endpoint to call. The result of the first one will be the parameter to the second one. For the second API, it will return a result with "hasMore" value. If this value is true, I should change the pagination parameters and call the second API again. The demo code is the following:

 client.getApi1()
        .map(r -> r.getResult())
        .flatMap(p -> client.getApi2(p, 2(page size), 1(page start)))
        .subscribe(r -> System.out.println(r.isHasmore()));

How to repeat calling the second API (getApi2) until "hasMore" is false.

Besides, I need to change the parameters page size and page start

Answer 1

Try this code:

 AtomicInteger pageCounter = new AtomicInteger(0);
 client.getApi1()
    .map(r -> r.getResult())
    .flatMap(p -> client.getApi2(p, 2(page size), pageCounter.incrementAndGet()))
    .repeat()            
    .takeWhile(r -> r.isHasmore())
    .subscribe(r -> System.out.println(r.isHasmore()));

repeat() calls getApi2 infinitely. takeWhile(continuePredicate) relays values while a continuePredicate (r.isHasmore()) returns true

Answer 2

I find a solution by use expand operator. But, need to do some change on my API call. The response from the getApi2 need to return last page size and last page start.

    client.getApi1()
        .map(r -> r.getResult())
        .getApi2(p, 2, 1)
        .expand(res -> {
            if (res.isHasmore()) {
                return client.getApi2(orgId, res.getPageSize(), res.PageStart() + 1);
            }
            return Flux.empty();
        });