Pagination in Java Reactive Programming [closed]

Question

I am still new in Java Reactive Programming and my project Requirement wants me to implement Pagination with Reactive Programming in Java.

Like if I hit an API which returns me 10000 records in stream then I needs to return a flux with proper pagination.

Can anyone suggest me a good approach about this?

Like this is the approach that I am following.

Repository

  public interface CouchBaseRepository extends ReactiveCouchBaseRepository<Book,Integer> {
   @Query("#{#n1ql.selectEntity} where name=$1")
   public Flux<Book> getPaginatedFlux(String name ,final Pageable pageable);

This is my Repositorty but when I up my application then it shows this following error.

    java.lang.IllegalStateException: Method has to have one of the following return types! [interface org.springframework.data.domain.Page, interface org.springframework.data.domain.Slice, interface java.util.List]

I cannot use Page inteface here as it is blocking so Is there any way to deal with this problem?

Answer 1

I haven't worked with spring-webflux yet, so I can't comment on specific API calls, but I'll provide a "theoretical" answer that might help as well.

Flux represents a stream of data (possibly infinite). So, pagination is kind of not consistent with reactivity, only because they're talking about different things

Consider implementing pagination with input parameters (like usual limit/offset) in the method that returns Flux of (logically decided) up to 10000 records as per your requirement.

So, one call will be handled in a "reactive manner" but it will return only one page of data, if you want to load another page - do another reactive call.

Of course at the level of streams, after 10000 objects receive, the stream should be closed. This is the approach I suggest.

There is an another option: implement everything via one stream, but in this case the client side (UI or whatever that consumes the paged data) will have to be "smart enough" to load /unload only the required data. In other words, if all-in-all you have, say 1 million objects to show, think whether you should avoid situation where all 1 million is loaded on client side at once.

In addition the page navigation will be kind of tricky (stuff like, get next/previous page). I haven't worked like this before. I think bottom line, the choice will be requirement driven.