用java实现application/octet-stream请求，方式为POST，文件流是 easyexcel动态写入，请求头中有filename参数支持中文

可以使用Java中的HttpURLConnection类进行POST请求，并设置请求头中的filename参数。示例代码如下：

import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;

public class PostOctetStreamRequest {
    public static void main(String[] args) throws Exception {
        String urlStr = "http://example.com/upload";
        String fileName = "测试文件.xlsx"; // 中文文件名
        String boundary = "Boundary" + System.currentTimeMillis(); // 分隔符

        URL url = new URL(urlStr);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setRequestMethod("POST");
        conn.setDoOutput(true);
        conn.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + boundary);

        OutputStream outputStream = conn.getOutputStream();
        PrintWriter writer = new PrintWriter(new OutputStreamWriter(outputStream, "UTF-8"), true);

        // 添加文件流
        writer.println("--" + boundary);
        writer.println("Content-Disposition: form-data; name=\"file\"; filename=\"" + fileName + "\"");
        writer.println("Content-Type: application/octet-stream");
        writer.println();
        EasyExcel.write(outputStream, Object.class).sheet().doWrite(dataList); // EasyExcel动态写入文件流
        writer.println();
        writer.flush();

        // 添加分隔符和结束符
        writer.println("--" + boundary + "--");
        writer.close();

        // 获取响应结果
        BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
        String line;
        StringBuilder result = new StringBuilder();
        while ((line = reader.readLine()) != null) {
            result.append(line);
        }
        reader.close();

        System.out.println(result.toString());
    }
}

通过这样的方式，你可以使用Java语言实现application/octet-stream请求，实现动态写入文件流并携带请求头参数，支持中文文件名。