Accept Payments with Paystack in Spring Boot

Add your key to application.properties:

paystack.secret-key=sk_test_xxxxxxxxxxxxxxxxxxxxx

// src/main/java/com/example/payment/PaystackService.java
@Service
public class PaystackService {
    @Value("${paystack.secret-key}")
    private String secretKey;

    private final RestTemplate restTemplate = new RestTemplate();

    public Map<String, Object> initializeTransaction(String email, int amountKobo, String reference, String callbackUrl) {
        HttpHeaders headers = new HttpHeaders();
        headers.set("Authorization", "Bearer " + secretKey);
        headers.setContentType(MediaType.APPLICATION_JSON);

        Map<String, Object> body = Map.of(
            "email", email,
            "amount", amountKobo,
            "reference", reference,
            "callback_url", callbackUrl
        );

        HttpEntity<Map<String, Object>> request = new HttpEntity<>(body, headers);
        ResponseEntity<Map> response = restTemplate.postForEntity(
            "https://api.paystack.co/transaction/initialize", request, Map.class);

        return response.getBody();
    }

    public Map<String, Object> verifyTransaction(String reference) {
        HttpHeaders headers = new HttpHeaders();
        headers.set("Authorization", "Bearer " + secretKey);

        HttpEntity<?> request = new HttpEntity<>(headers);
        ResponseEntity<Map> response = restTemplate.exchange(
            "https://api.paystack.co/transaction/verify/" + reference,
            HttpMethod.GET, request, Map.class);

        return response.getBody();
    }
}

@RestController
@RequestMapping("/api/payment")
public class PaymentController {
    @Autowired
    private PaystackService paystackService;

    @PostMapping("/initialize")
    public ResponseEntity<?> initialize(@RequestBody Map<String, Object> payload) {
        String email = (String) payload.get("email");
        double amount = ((Number) payload.get("amount")).doubleValue();
        String reference = "order_" + UUID.randomUUID().toString().substring(0, 12);

        Map<String, Object> result = paystackService.initializeTransaction(
            email, (int)(amount * 100), reference, "http://localhost:8080/api/payment/callback");

        if (Boolean.TRUE.equals(result.get("status"))) {
            Map<String, Object> data = (Map<String, Object>) result.get("data");
            return ResponseEntity.ok(Map.of(
                "authorization_url", data.get("authorization_url"),
                "reference", data.get("reference")
            ));
        }
        return ResponseEntity.badRequest().body(Map.of("error", result.get("message")));
    }

    @GetMapping("/callback")
    public ResponseEntity<?> callback(@RequestParam String reference) {
        Map<String, Object> result = paystackService.verifyTransaction(reference);

        if (Boolean.TRUE.equals(result.get("status"))) {
            Map<String, Object> data = (Map<String, Object>) result.get("data");
            if ("success".equals(data.get("status"))) {
                // TODO: Verify amount, mark order as paid
                return ResponseEntity.ok(Map.of("success", true));
            }
        }
        return ResponseEntity.badRequest().body(Map.of("success", false));
    }
}

1. Use profiles. Spring profiles for dev/prod keys: application-dev.properties vs application-prod.properties.
2. Set up webhooks. See Handle Paystack Webhooks in Spring Boot.
3. HTTPS. Required for callbacks and webhooks.
4. Validate amounts. Check against your JPA entity, not request params.

This guide is part of the Paystack integration guides by language and framework series.

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