Send OTP via SMS from Java and Spring Boot

We already published hands-on guides for Node.js, Python, and PHP/Laravel. This article is the Java / Spring Boot counterpart—new code samples, not copy-pasted explanations of DLT or pricing.

Why This Guide Exists

Enterprise and fintech teams in India often standardize on JVM backends. They need a Spring-friendly shape: beans, properties, and HTTP clients that fit existing patterns. See API documentation for exact paths and headers.

Configuration and Secrets

Store the API key in environment variables or Spring Cloud Secret—not in source control. Align with key rotation practices.

# application.yml (example)
startmessaging:
  api-key: ${STARTMESSAGING_API_KEY}
  base-url: https://api.startmessaging.com

Send OTP Request

Use Spring 6.1+ RestClient to POST JSON matching your template. Replace placeholders with your template ID and variables.

record OtpSendRequest(
    String phoneNumber,
    String templateId,
    Map<String, String> variables
) {}

// RestClient bean
public OtpSendResponse sendOtp(OtpSendRequest body) {
  return restClient.post()
      .uri("/otp/send")
      .header("X-API-Key", apiKey)
      .body(body)
      .retrieve()
      .body(OtpSendResponse.class);
}

Map response fields to your persistence layer the same way you would in Node or Python: store requestId for verification and status polling.

Verify and Status

Follow the same verification sequence as in the OTP verification flow. Use idempotency keys on send if your client retries POST requests.

Next Steps

Add integration tests with mocks per staging and testing OTP, then wire Spring Security so only authenticated admins can trigger bulk test sends.

FAQ

See FAQ above.