public static void signature() {
    long timestamp = System.currentTimeMillis();
    String taskId = "xxxx";
    String aliUid = "xxxxx";
    // 將 taskId=xxx&timestamp=xxx&aliUid=xxx 進(jìn)行 md5 + base64 加密，放在 signature 字段
    String signature;
    try {
        signature = URLEncoder.encode(md5Base64("taskId=" + taskId + "&timestamp=" + timestamp + "&aliUid=" + aliUid), "utf-8");
        System.out.println(signature);
    } catch (Exception e) {
        e.printStackTrace();
    }
}

public static String md5Base64(String str) throws NoSuchAlgorithmException {
    //string 編碼必須為 utf-8
    byte[] utfBytes = str.getBytes(StandardCharsets.UTF_8);
    MessageDigest mdTemp = MessageDigest.getInstance("MD5");
    mdTemp.update(utfBytes);
    byte[] md5Bytes = mdTemp.digest();
    return Base64.encodeBase64String(md5Bytes);
}