Spring WebClient多部分/表单数据请求，无法发送文件

import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.http.client.reactive.ReactorClientHttpConnector;
import org.springframework.util.MultiValueMap;
import org.springframework.web.reactive.function.BodyInserters;
import org.springframework.web.reactive.function.client.WebClient;
import reactor.core.publisher.Mono;
import reactor.netty.http.client.HttpClient;

import java.io.File;

public class WebClientExample {
    public static void main(String[] args) {
        // 创建一个WebClient实例
        WebClient webClient = WebClient.builder()
                .clientConnector(new ReactorClientHttpConnector(HttpClient.create()))
                .build();

        // 构建请求体
        MultiValueMap<String, Object> parts = new MultipartBodyBuilder()
                .part("file", new File("path/to/file"))
                .build();

        // 发送请求
        webClient.post()
                .uri("http://example.com/upload")
                .contentType(MediaType.MULTIPART_FORM_DATA)
                .body(BodyInserters.fromMultipartData(parts))
                .retrieve()
                .bodyToMono(String.class)
                .subscribe(response -> {
                    // 处理响应
                    System.out.println(response);
                });
    }
}