public String post(String actionUrl, Map<String, String> params) throws IOException {

        String BOUNDARY = java.util.UUID.randomUUID().toString();
        String PREFIX = "--";
        String 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(30 * 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);
        StringBuilder sb = new StringBuilder();
        if (params!=null) {
            // 首先组拼文本类型的参数
            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());
        if (!TextUtils.isEmpty(sb.toString())) {
            outStream.write(sb.toString().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();
        InputStream in = conn.getInputStream();
        if (res == 200) {
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(in, "UTF-8"));
            StringBuffer buffer = new StringBuffer();
            String line = "";
            while ((line = bufferedReader.readLine()) != null){
                buffer.append(line);
            }

//          int ch;
//          StringBuilder sb2 = new StringBuilder();
//          while ((ch = in.read()) != -1) {
//              sb2.append((char) ch);
//          }
            return buffer.toString();
        }
        outStream.close();
        conn.disconnect();
        return in.toString();
    }