Kiskae / RxJava2Batched

Implementation of a Flowable that allows batched requests.

RxJava2Batched

Implementation of a Flowable that allows batched requests.

Examples:

Paginated by offset:

private final static int RESULTS_PER_PAGE = 100;
private Flowable<Data> getPage(Integer offset, Integer limit);

Flowable<Data> stream() {
    return FlowableBatched.create(Functions.justCallable(0), (currentOffset, requested, output) -> {
        int toEmit = (int) Math.min(requested, RESULTS_PER_PAGE);
        ConnectableFlowable<Data> data = getPage(currentOffset, toEmit);
        
        // Connecting to the publisher begins the stream
        output.setSource(data.autoConnect());
        
        // Lets presume a result with no items indicates the end.
        output.setState(data.count().filter(count -> count != 0).map(count -> currentOffset + count + 1));
    });
}

stream().take(111); // Will request 100 and then 11 items

Paginated by token:

class PageWithData {
    String nextToken;
    List<Data> items;
}

// null for initial page
private Flowable<PageWithData> getPage(String token);

Flowable<Data> stream() {
    return FlowableBatched.create(Functions.justCallable(""), (token, requested, output) -> {
        ConnectableFlowable<PageWithData> data = getPage(token.isEmpty() ? null : token);
        
        // Connecting to the publisher begins the stream
        output.setSource(data.autoConnect().flatMapIterable(page -> page.items));
        
        // Lets presume a result with no items indicates the end.
        output.setState(
                data.lastElement()
                    .map(page -> page.nextToken) // Extract token
                    .filter(token -> !token.isEmpty()) // Lack of a next token means end of stream
        ); 
    });
}