android上傳文件到服務器的一個方法

public String fileUpload(String url, Map<String, String> params,
            Map<String, File> files // <參數名，文件>形式
    ) 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(url);
        HttpURLConnection conn = (HttpURLConnection) uri.openConnection();
        conn.setReadTimeout(10 * 1000);
        conn.setDoInput(true);// 允許輸入
        conn.setDoOutput(true);// 允許輸出
        conn.setUseCaches(false);
        conn.setRequestMethod("POST"); // Post方式
        conn.setRequestProperty("connection", "keep-alive");
        conn.setRequestProperty("Charsert", "UTF-8");
        conn.setRequestProperty("Content-Type", MULTIPART_FROM_DATA
                + ";boundary=" + BOUNDARY);
        // 首先組拼文本類型的參數
        StringBuilder sb = new StringBuilder();
        if (params != null) {
            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());
        // 發送文件數據
        if (files != null)
            for (Map.Entry<String, File> file : files.entrySet()) {
                String paramName = file.getKey();
                File f = file.getValue();
                StringBuilder sb1 = new StringBuilder();
                sb1.append(PREFIX);
                sb1.append(BOUNDARY);
                sb1.append(LINEND);
                sb1.append("Content-Disposition: form-data; name=\""
                        + paramName + "\"; filename=\"" + f.getName() + "\""
                        + LINEND);
                sb1.append("Content-Type: application/octet-stream; charset="
                        + CHARSET + LINEND);
                sb1.append(LINEND);
                outStream.write(sb1.toString().getBytes());
                InputStream is = new FileInputStream(f);
                byte[] buffer = new byte[4 * 1024];
                int len = 0;
                while ((len = is.read(buffer)) != -1) {
                    outStream.write(buffer, 0, len);
                }
                is.close();
                outStream.write(LINEND.getBytes());
            }
        // 請求結束標誌
        byte[] end_data = (PREFIX + BOUNDARY + PREFIX + LINEND).getBytes();
        outStream.write(end_data);
        outStream.flush();
        // 得到響應碼
        int res = conn.getResponseCode();
        InputStream in = conn.getInputStream();
        InputStreamReader isReader = new InputStreamReader(in);
        BufferedReader bufReader = new BufferedReader(isReader);
        String line = null;
        StringBuffer sb2 = new StringBuffer();
        if (res == 200) {
            while ((line = bufReader.readLine()) != null) {
                sb2.append(line);
            }
        }
        outStream.close();
        in.close();
        conn.disconnect();
        return sb2.toString();
    }