Explication détaillée des exemples d'envoi de fichiers et d'informations de chaîne par Java HttpURLConnection

/**
   * 通过拼接的方式构造请求内容，实现参数传输以及文件传输
   * 
   * @param actionUrl 访问的服务器URL
   * @param params 普通参数
   * @param files 文件参数
   * @return
   * @throws IOException
   */
  public static void post(String actionUrl, Map<String, String> params, Map<String, File> files) throws IOException
  {

    String BOUNDARY = java.util.UUID.randomUUID().toString();
    String PREFIX = "--", LINEND = "\r\n";
    String MULTIPART_FROM_DATA = "multipart/form-data";
    String CHARSET = "UTF-8";

    URL uri = new URL(actionUrl);
    HttpURLConnection conn = (HttpURLConnection) uri.openConnection();
    conn.setReadTimeout(5 * 1000); // 缓存的最长时间
    conn.setDoInput(true);// 允许输入
    conn.setDoOutput(true);// 允许输出
    conn.setUseCaches(false); // 不允许使用缓存
    conn.setRequestMethod("POST");
    conn.setRequestProperty("connection", "keep-alive");
    conn.setRequestProperty("Charsert", "UTF-8");
    conn.setRequestProperty("Content-Type", MULTIPART_FROM_DATA + ";boundary=" + BOUNDARY);

    // 首先组拼文本类型的参数
    StringBuilder sb = new StringBuilder();
    for (Map.Entry<String, String> entry : params.entrySet())
    {
      sb.append(PREFIX);
      sb.append(BOUNDARY);
      sb.append(LINEND);
      sb.append("Content-Disposition: form-data; name=\"" + entry.getKey() + "\"" + LINEND);
      sb.append("Content-Type: text/plain; charset=" + CHARSET + LINEND);
      sb.append("Content-Transfer-Encoding: 8bit" + LINEND);
      sb.append(LINEND);
      sb.append(entry.getValue());
      sb.append(LINEND);
    }

    DataOutputStream outStream = new DataOutputStream(conn.getOutputStream());
    outStream.write(sb.toString().getBytes());
    InputStream in = null;
    // 发送文件数据
    if (files != null)
    {
      for (Map.Entry<String, File> file : files.entrySet())
      {
        StringBuilder sb1 = new StringBuilder();
        sb1.append(PREFIX);
        sb1.append(BOUNDARY);
        sb1.append(LINEND);
        // name是post中传参的键 filename是文件的名称
        sb1.append("Content-Disposition: form-data; name=\"file\"; filename=\"" + file.getKey() + "\"" + LINEND);
        sb1.append("Content-Type: application/octet-stream; charset=" + CHARSET + LINEND);
        sb1.append(LINEND);
        outStream.write(sb1.toString().getBytes());

        InputStream is = new FileInputStream(file.getValue());
        byte[] buffer = new byte[1024];
        int len = 0;
        while ((len = is.read(buffer)) != -1)
        {
          outStream.write(buffer, 0, len);
        }

        is.close();
        outStream.write(LINEND.getBytes());
      }

      // 请求结束标志
      byte[] end_data = (PREFIX + BOUNDARY + PREFIX + LINEND).getBytes();
      outStream.write(end_data);
      outStream.flush();
      // 得到响应码
      int res = conn.getResponseCode();
      if (res == 200)
      {
        in = conn.getInputStream();
        int ch;
        StringBuilder sb2 = new StringBuilder();
        while ((ch = in.read()) != -1)
        {
          sb2.append((char) ch);
        }
      }
      outStream.close();
      conn.disconnect();
    }
    // return in.toString();
  }