从2016年的阅读谷歌群帖中可以看出：“.map（）已转换为.via（）”
源代码：https://groups.google.com/g/akka-user/c/EzHygZpcCHg
下列代码行是否等效：

Source.repeat(json).take(3).via(mapToDtoFlow).to(printSink).run(actorSystem);
Source.repeat(json).take(3).map(x -> mapper.readValue(x, RequestDto.class)).to(printSink).run(actorSystem);

是否存在应使用图而非流的情况？
源代码：
请求DTO：

import com.fasterxml.jackson.annotation.JsonFormat;
import lombok.Builder;
import lombok.Getter;
import lombok.Setter;
import lombok.ToString;
import lombok.extern.jackson.Jacksonized;

import java.util.Date;

@Getter
@Setter
@Builder
@ToString
@Jacksonized
public class RequestDto {
    @JsonFormat(pattern = "yyyy-MM-dd HH:mm:sss")
    private final Date datePurchased;
}

StreamManager（包含主方法）：

import akka.Done;
import akka.NotUsed;
import akka.actor.typed.ActorSystem;
import akka.actor.typed.javadsl.Behaviors;
import akka.stream.javadsl.Flow;
import akka.stream.javadsl.Sink;
import akka.stream.javadsl.Source;
import com.fasterxml.jackson.databind.ObjectMapper;

import java.util.concurrent.CompletionStage;

public class StreamManager {

    final static ObjectMapper mapper = new ObjectMapper();

    private static final Flow<String, RequestDto, NotUsed> mapToDtoFlow = Flow.of(String.class)
            .map(input -> mapper.readValue(input, RequestDto.class))
            .log("error");

    public static void main(String args[]) {

        final ActorSystem actorSystem = ActorSystem.create(Behaviors.empty(), "actorSystem");
        final Sink<RequestDto, CompletionStage<Done>> printSink = Sink.foreach(System.out::println);

        final String json = "{\"datePurchased\":\"2022-03-03 21:32:017\"}";

        Source.repeat(json).take(3).via(mapToDtoFlow).to(printSink).run(actorSystem);
        Source.repeat(json).take(3).map(x -> mapper.readValue(x, RequestDto.class)).to(printSink).run(actorSystem);

    }

}