Akka提供了一个名为akka.http.javadsl.model.multipart.FormData的类来处理多部分表单数据。以下是一个示例代码，用于在Java中构建一个多部分表单HTTP请求：

import akka.http.javadsl.Http;
import akka.http.javadsl.marshallers.jackson.Jackson;
import akka.http.javadsl.model.HttpEntities;
import akka.http.javadsl.model.HttpRequest;
import akka.http.javadsl.model.MediaTypes;
import akka.http.javadsl.model.Multipart;
import akka.http.javadsl.model.RequestEntity;
import akka.japi.Pair;
import akka.stream.Materializer;
import akka.stream.javadsl.FileIO;
import akka.stream.javadsl.Source;
import akka.util.ByteString;

import java.io.File;
import java.util.Arrays;
import java.util.List;
import java.util.concurrent.CompletableFuture;
import java.util.stream.Collectors;

public class MultiPartFormRequestExample {

    private static final String URL = "https://example.com/upload";
    private static final String PARAM1_NAME = "param1";
    private static final String PARAM1_VALUE = "value1";
    private static final String PARAM2_NAME = "param2";
    private static final String PARAM2_VALUE = "value2";
    private static final String FILE1_PATH = "/path/to/file1";
    private static final String FILE2_PATH = "/path/to/file2";

    public static void main(String[] args) {
        Http http = Http.get();
        Materializer materializer = Materializer.createMaterializer(http.system());

        List>> files = Arrays.asList(
                new Pair<>("file1.txt", FileIO.fromPath(new File(FILE1_PATH).toPath())),
                new Pair<>("file2.txt", FileIO.fromPath(new File(FILE2_PATH).toPath()))
        );

        Multipart.FormData formData = Multipart.FormData.create()
                .withFormField(PARAM1_NAME, PARAM1_VALUE)
                .withFormField(PARAM2_NAME, PARAM2_VALUE)
                .withEntity(getMultiPartEntity(files));

        HttpRequest request = HttpRequest.POST(URL).withEntity(formData.toEntity());

        CompletableFuture futureResponse = http.singleRequest(request, materializer)
                .thenCompose(response -> response.entity().toStrict(1000, materializer))
                .thenApply(entity -> entity.getData().utf8String())
                .toCompletableFuture();

        futureResponse.thenAccept(System.out::println).join();

        http.shutdownAllConnectionPools()
                .thenCompose(done -> http.shutdownAllConnectionGroups())
                .whenComplete((done, exception) -> http.shutdown());
    }

    private static RequestEntity getMultiPartEntity(List>> files) {