javaspringproject-reactorreactivewebflux

Project reactor, Convert Flux into Map<String,List<Data>>

I have a list of Data object

public class Data{
    private String id;
    private String sharedId;
}

How to convert this list into Map<String,List<Data>>, collecting the data object sharing the same sharedId together

I have tried to use this line of code, but no luck

Map<String,List<Data>> dataMap= Flux.fromIterable(list)
        .collectMap(item-> item.getSharedId(),
                item-> item);
Solution

  • Stream API is not equal to Reactive API and they are not interchangeable.

    Use Stream API for grouping into Map<String, List<Data>> from List<Data>:

    Map<String,List<Data>> dataMap = list.stream()
    .collect(Collectors.groupingBy(Data::getSharedId));

    Using Reactive API to achieve you achieve Flux<GroupedFlux<String, Data>> analogically or expand the structure using Map.Entry:

    Flux<GroupedFlux<String, Data>> groupedFlux = Flux.fromIterable(list)
    .groupBy(Data::getSharedId);

    Flux<Map.Entry<String, List<Data>>> groupedFlux = Flux.fromIterable(list)
    .groupBy(Data::getSharedId)
    .flatMap(group -> group
        .collectList()
        .map(listOfData -> Map.entry(group.key(), listOfData)));