java 模拟表单方式提交上传文件

/**
 * 模拟form表单的形式 ，上传文件 以输出流的形式把文件写入到url中，然后用输入流来获取url的响应
 *
 * @param url      请求地址 form表单url地址
 * @param filePath 文件在服务器保存路径
 * @return String url的响应信息返回值
 * @throws IOException
 */
public static RestResponse filePost(String url, String filePath){
    String result = null;
    File file = new File(filePath);
    RestResponse restResponse = new RestResponse();
    try {
        if (!file.exists() || !file.isFile()) {
            throw new IOException("文件不存在");
        }
        URL urlObj = new URL(url);
        // 连接
        HttpURLConnection con = (HttpURLConnection) urlObj.openConnection();
        /**
         * 设置关键值
         */
        con.setRequestMethod("POST"); // 以Post方式提交表单，默认get方式
        con.setDoInput(true);
        con.setDoOutput(true);
        con.setUseCaches(false); // post方式不能使用缓存
        // 设置请求头信息
        con.setRequestProperty("charset", "UTF-8"); 
        con.setRequestProperty("accept", "application/json");
        con.setRequestProperty("Content-length", String.valueOf(file.length()));
        // 设置边界
        String BOUNDARY = "----------" + System.currentTimeMillis();
        con.setRequestProperty("Content-Type", "multipart/form-data; boundary="+ BOUNDARY);
        // 请求正文信息
        // 第一部分：
        StringBuilder sb = new StringBuilder();
        sb.append("--"); // 必须多两道线
        sb.append(BOUNDARY);
        sb.append("\r\n");
        sb.append("Content-Disposition: form-data;name=\"file\";filename=\""
                + file.getName() + "\"\r\n");
        sb.append("Content-Type:application/octet-stream\r\n\r\n");
        byte[] head = sb.toString().getBytes("utf-8");
        // 获得输出流
        OutputStream out = new DataOutputStream(con.getOutputStream());
        // 输出表头
        out.write(head);
        // 文件正文部分
        // 把文件已流文件的方式 推入到url中
        DataInputStream in = new DataInputStream(new FileInputStream(file));
        int bytes = 0;
        byte[] bufferOut = new byte[1024];
        while ((bytes = in.read(bufferOut)) != -1) {
            out.write(bufferOut, 0, bytes);
        }
        in.close();
        // 结尾部分
        byte[] foot = ("\r\n--" + BOUNDARY + "--\r\n").getBytes("utf-8");// 定义最后数据分隔线
        out.write(foot);
        out.flush();
        out.close();
        BufferedReader reader = null;
        try {
            //返回值
            int resultCode = con.getResponseCode();
            restResponse.setCode(resultCode);
            restResponse.setMessage(con.getResponseMessage());
            restResponse.setResponseBody(result);
        } catch (IOException e) {
            restResponse.setCode(HttpStatus.GONE.value());
            restResponse.setMessage(e.toString());
            logger.error(e.toString());
        } finally {
            if (reader != null) {
                reader.close();
            }
        }
    }catch (IOException e2){
        restResponse.setCode(HttpStatus.GONE.value());
        restResponse.setMessage(e2.toString());
        logger.error(e2.toString());
    }
    return restResponse;
}
public static void main(String[] args) throws IOException {
    String filePath = "D:/logs/logs2.log";
    String sendUrl = "http://127.0.0.1:30014/api/v1/fileSystem/io" +
            "?path=hdfs://nameservice1/tmp/CGC/userFile/tmp/CGC/jobs/ff939a74-f8b9-45f2-8b6c-6e2f4a0e5efb/logs3.log&chunkSize=16384&overwrite=true";
    HttpRequestUtil fileUpload = new HttpRequestUtil();
    fileUpload.filePost(sendUrl,filePath); 
}