Introduction
Getting started
There are 3 major steps involved in the integration process for paystack payment gateway API
- Authentication
- Initiate Transaction
- Verify Transaction
Getting SECRET Key
Every API call has to be authenticated, what this means is that when making a call to any of the API’s, you need to pass an Authorization key in your header. In this case, the key would be your secret key.
To get your secret key, you need to create an account with paystack using this link. Once your signup has been completed, login to your dashboard and navigate to settings, you should find a tab called “API Keys and Webhooks”, that’s where you can get your test key.
Initializing a transaction
Here’s the part where I integrate with an API, the initialize transaction endpoint.
Code structure
The first thing I do is to create a request DTO, this DTO would be used to map the request body to be sent to paystack’s API. For this endpoint, there are 2 compulsory fields and some optional fields but I would be working with only the compulsory fields; amount and email.
InitializeTransactionRequest
public class PaystackInitializeTransactionRequest {
private String email;
private String amount;
public PaystackInitializeTransactionRequest(String currency, String reference) {
this.email = email;
this.amount = amount;
}
public PaystackInitializeTransactionRequest() {
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public String getAmount() {
return amount;
}
public void setAmount(String amount) {
this.amount = amount;
}
}
Now that I have the request structure, I’d proceed to make a call to the endpoint in my service implementation class using rest template.
I mentioned earlier that you need your secret key to make a call to any of the API’s. In the code snippet below, I pass the secret key in my header as the Authorization value as specified in the documentation.
RestTemplate restTemplate = new RestTemplate();
String secretkey = "sk_test_b2*********************";
public ResponseEntity<Object> initializeTransaction
(PaystackInitializeTransactionRequest request) {
String url = "https://api.paystack.co/transaction/initialize";
HttpHeaders headers = new HttpHeaders();
headers.set("Authorization", "Bearer " + "" + secretkey);
HttpEntity<PaystackInitializeTransactionRequest> httpEntity = new HttpEntity<>(request, headers);
ResponseEntity<Object> result = restTemplate.postForEntity(url, httpEntity, Object.class);
return result;
}
Controller
The next thing is to write the controller code.
@RestController
@RequestMapping("/paystack")
public class PaystackController {
@Autowired
PaystackImpl paystackImplementation;
@PostMapping(path= "/initializetransaction", produces = "application/json")
ResponseEntity<Object> initializeTransaction
(@RequestBody PaystackInitializeTransactionRequest request){
return paystackImplementation.initializeTransaction(request);
}
Testing the integration
To test the integration, I used postman. There are two important fields in the response;
- authorization_url: this is the url your customers would use to make payment
- reference: you need to keep track of this reference because you need it when trying to verify/check the status of your transaction
Testing the authorization url
To test the authorization url, copy it and paste it on a browser. You would notice that the amount and email shown are the same with what you specified when making the request
Verifying Transaction
This is the endpoint to call when you want to check the status of your transaction. This is a GET request so there is no request body, just a path variable specifying the reference of the transaction.
CODE STRUCTURE
public ResponseEntity<Object> verifyTransaction(String reference){
String url = "https://api.paystack.co/transaction/verify/" + reference;
HttpHeaders headers = new HttpHeaders();
headers.set("Authorization", "Bearer " + "" + secretkey);
HttpEntity request = new HttpEntity(headers);
ResponseEntity<Object> responseEntity = restTemplate.exchange(
url,
HttpMethod.GET,
request,
Object.class
);
return responseEntity;
} COntroller
@RestController
@RequestMapping("/paystack")
public class PaystackController {
@Autowired
PaystackImpl paystackImplementation;
@GetMapping(path= "/verifytransaction/{reference}", produces = "application/json")
ResponseEntity<Object> verifyTransaction
(@PathVariable String reference){
return paystackImplementation.verifyTransaction(reference);
}
Testing the integration
Summary
There are better ways to revamp this code, however, this is a simplified code to help you with your integration. I hope this has been helpful. Cheers!
