How to Build a Java SMS Verification Service with Random Codes and HTTP Calls

1

Construct mobile verification code: use Random to generate a 4‑digit number between 1000 and 9999. 2 Send the phone number and code to an SMS platform via its API (parameters: target phone, code, optional expiration, API URL, token). 3 Store the platform’s JSON response as an object. 4 Save phone‑number, code and timestamp in the session for later validation. 5 Receive the user‑entered code and other data. 6 Compare the submitted code with the session value and check its validity period. 7 If the code matches and is within the time window, allow the request to proceed.

1. Add the required JAR

<dependency>
  <groupId>commons-codec</groupId>
  <artifactId>commons-codec</artifactId>
  <version>1.11</version>
</dependency>

Below is a sample config file that stores parameters needed for the SMS service.

2. Implement an HTTP request utility

public class HttpUtil {
    /** Construct common parameters timestamp, sig and respDataType */
    public static String createCommonParam() {
        // timestamp
        SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMddHHmmss");
        String timestamp = sdf.format(new Date());

        // signature
        String sig = DigestUtils.md5Hex(Config.ACCOUNT_SID + Config.AUTH_TOKEN + timestamp);
        return "timestamp=" + timestamp + "&sig=" + sig + "&respDataType=" + Config.RESP_DATA_TYPE;
    }

    /** POST request */
    public static String post(String url, String body) {
        System.out.println("url:" + System.lineSeparator() + url);
        System.out.println("body:" + System.lineSeparator() + body);
        String result = "";
        try {
            OutputStreamWriter out = null;
            BufferedReader in = null;
            URL realUrl = new URL(url);
            URLConnection conn = realUrl.openConnection();
            conn.setDoOutput(true);
            conn.setDoInput(true);
            conn.setConnectTimeout(5000);
            conn.setReadTimeout(20000);
            conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
            out = new OutputStreamWriter(conn.getOutputStream(), "UTF-8");
            out.write(body);
            out.flush();

            in = new BufferedReader(new InputStreamReader(conn.getInputStream(), "UTF-8"));
            String line;
            boolean firstLine = true;
            while ((line = in.readLine()) != null) {
                if (firstLine) {
                    firstLine = false;
                } else {
                    result += System.lineSeparator();
                }
                result += line;
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return result;
    }

    /** Callback test method */
    public static String postHuiDiao(String url, String body) {
        String result = "";
        try {
            OutputStreamWriter out = null;
            BufferedReader in = null;
            URL realUrl = new URL(url);
            URLConnection conn = realUrl.openConnection();
            conn.setDoOutput(true);
            conn.setDoInput(true);
            conn.setConnectTimeout(5000);
            conn.setReadTimeout(20000);
            out = new OutputStreamWriter(conn.getOutputStream(), "UTF-8");
            out.write(body);
            out.flush();

            in = new BufferedReader(new InputStreamReader(conn.getInputStream(), "UTF-8"));
            String line;
            boolean firstLine = true;
            while ((line = in.readLine()) != null) {
                if (firstLine) {
                    firstLine = false;
                } else {
                    result += System.lineSeparator();
                }
                result += line;
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return result;
    }
}

3. Generate a four‑digit random code

public static String runNumber() {
    String chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    StringBuilder sb = new StringBuilder(4);
    for (int i = 0; i < 4; i++) {
        char ch = chars.charAt(new Random().nextInt(chars.length()));
        sb.append(ch);
    }
    System.out.println(sb.toString());
    return sb.toString();
}

4. Send the verification SMS

public class IndustrySMS {
    private static String operation = "/industrySMS/sendSMS";
    private static String accountSid = Config.ACCOUNT_SID;
    private static String to = "15342349382";
    private static String smsContent = "【小陶科技】登录验证码：{" + runNumber() + "}，如非本人操作，请忽略此短信。";

    /** Send verification code */
    public static void execute() {
        String tmpSmsContent = null;
        try {
            tmpSmsContent = URLEncoder.encode(smsContent, "UTF-8");
        } catch (Exception e) { }
        String url = Config.BASE_URL + operation;
        String body = "accountSid=" + accountSid + "&to=" + to + "&smsContent=" + tmpSmsContent
                + HttpUtil.createCommonParam();
        String result = HttpUtil.post(url, body);
        System.out.println("result:" + System.lineSeparator() + result);
    }
}