Payment Plugin Overview

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public class GoCardlessPaymentPluginApi implements PaymentPluginApi {
	private static final Logger logger = LoggerFactory.getLogger(GoCardlessPaymentPluginApi.class);
	private OSGIKillbillAPI killbillAPI;
	private Clock clock;
	private static String GC_ACCESS_TOKEN_PROPERTY = "GC_ACCESS_TOKEN";
    private GoCardlessClient client;
    public GoCardlessPaymentPluginApi(final OSGIKillbillAPI killbillAPI,final Clock clock) {
		this.killbillAPI = killbillAPI;
		this.clock = clock;
		client = GoCardlessClient.newBuilder(System.getenv(GC_ACCESS_TOKEN_PROPERTY)).withEnvironment(GoCardlessClient.Environment.SANDBOX).build();
	}
	//other methods
}

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public class GoCardlessPaymentTransactionInfoPlugin extends PluginPaymentTransactionInfoPlugin{
	public GoCardlessPaymentTransactionInfoPlugin(UUID kbPaymentId, UUID kbTransactionPaymentPaymentId,
			TransactionType transactionType, BigDecimal amount, Currency currency, PaymentPluginStatus pluginStatus,
			String gatewayError, String gatewayErrorCode, String firstPaymentReferenceId,
			String secondPaymentReferenceId, DateTime createdDate, DateTime effectiveDate,
			List<PluginProperty> properties) {
		super(kbPaymentId, kbTransactionPaymentPaymentId, transactionType, amount, currency, pluginStatus, gatewayError,
				gatewayErrorCode, firstPaymentReferenceId, secondPaymentReferenceId, createdDate, effectiveDate, properties);
	}
}

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public HostedPaymentPageFormDescriptor buildFormDescriptor(UUID kbAccountId, Iterable<PluginProperty> customFields,
	Iterable<PluginProperty> properties, CallContext context) throws PaymentPluginApiException {
	logger.info("buildFormDescriptor, kbAccountId=" + kbAccountId);
	// retrieve properties
	String successRedirectUrl = PluginProperties.findPluginPropertyValue("success_redirect_url", properties); // "https://developer.gocardless.com/example-redirect-uri/"; - this is the URL to which GoCardless will redirect after users set up the mandate
	String redirectFlowDescription = PluginProperties.findPluginPropertyValue("redirect_flow_description",properties);
	String sessionToken = PluginProperties.findPluginPropertyValue("session_token", properties); PrefilledCustomer customer = buildCustomer(customFields);// build a PrefilledCuctomer object from custom fields if present
	RedirectFlow redirectFlow = client.redirectFlows().create().withDescription(redirectFlowDescription)
			.withSessionToken(sessionToken)
			.withSuccessRedirectUrl(successRedirectUrl).withPrefilledCustomer(customer).execute();
	logger.info("RedirectFlow Id", redirectFlow.getId());
	logger.info("RedirectFlow URL", redirectFlow.getRedirectUrl());
	PluginHostedPaymentPageFormDescriptor pluginHostedPaymentPageFormDescriptor = new PluginHostedPaymentPageFormDescriptor(
			kbAccountId, redirectFlow.getRedirectUrl());
	return pluginHostedPaymentPageFormDescriptor;
}

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public void addPaymentMethod(UUID kbAccountId, UUID kbPaymentMethodId, PaymentMethodPlugin paymentMethodProps,
		boolean setDefault, Iterable<PluginProperty> properties, CallContext context)
		throws PaymentPluginApiException {
	logger.info("addPaymentMethod, kbAccountId=" + kbAccountId);
	final Iterable<PluginProperty> allProperties = PluginProperties.merge(paymentMethodProps.getProperties(),
			properties);
	String redirectFlowId = PluginProperties.findPluginPropertyValue("redirect_flow_id", allProperties);  //retrieve the redirect flow ID
	String sessionToken = PluginProperties.findPluginPropertyValue("session_token", allProperties);
	try {
		//Use the redirect flow ID to "complete" the GoCardless flow
		RedirectFlow redirectFlow = client.redirectFlows().complete(redirectFlowId).withSessionToken(sessionToken).execute();
		String mandateId = redirectFlow.getLinks().getMandate(); //obtain mandate ID from the redirect flow
		logger.info("MandateId:", mandateId);
		try {
			//save Mandate ID in the Kill Bill database
			killbillAPI.getCustomFieldUserApi().addCustomFields(List.of(new PluginCustomField(kbAccountId,
					ObjectType.ACCOUNT, "GOCARDLESS_MANDATE_ID", mandateId, clock.getUTCNow())), context);
		} catch (CustomFieldApiException e) {
			logger.warn("Error occured while saving mandate id", e);
			throw new PaymentPluginApiException("Error occured while saving mandate id", e);
		}
	} catch (GoCardlessApiException e) {
		logger.warn("Error occured while completing the GoCardless flow", e.getType(), e);
		throw new PaymentPluginApiException("Error occured while completing the GoCardless flow", e);
	}
}

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public PaymentTransactionInfoPlugin purchasePayment(UUID kbAccountId, UUID kbPaymentId, UUID kbTransactionId,
		UUID kbPaymentMethodId, BigDecimal amount, Currency currency, Iterable<PluginProperty> properties,
		CallContext context) throws PaymentPluginApiException {
	logger.info("purchasePayment, kbAccountId=" + kbAccountId);
	PaymentTransactionInfoPlugin paymentTransactionInfoPlugin;
	String mandate = getMandateId(kbAccountId, context); // retrieve mandateId from Kill Bill tables
	logger.info("MandateId="+mandate);
	if (mandate != null) {
		logger.info("Processing payment");
		try {
			String idempotencyKey = PluginProperties.findPluginPropertyValue("idempotencykey", properties);
			com.gocardless.services.PaymentService.PaymentCreateRequest.Currency goCardlessCurrency = convertKillBillCurrencyToGoCardlessCurrency(
					currency);
			Payment payment = client.payments().create()
					.withAmount(Math.toIntExact(KillBillMoney.toMinorUnits(currency.toString(), amount)))
					.withCurrency(goCardlessCurrency).withLinksMandate(mandate).withIdempotencyKey(idempotencyKey)
					.withMetadata("kbPaymentId", kbPaymentId.toString()).withMetadata("kbTransactionId", kbTransactionId.toString()) //added for getPaymentInfo
					.execute();
			List<PluginProperty> outputProperties = new ArrayList<PluginProperty>();
			outputProperties.add(new PluginProperty("paymentId", payment.getId(), false));
			paymentTransactionInfoPlugin = new GoCardlessPaymentTransactionInfoPlugin(kbPaymentId, kbTransactionId,
					TransactionType.PURCHASE, amount, currency, PaymentPluginStatus.PROCESSED, null, null,
					String.valueOf(payment.getId()), null, new DateTime(), new DateTime(payment.getCreatedAt()),
					outputProperties);
			logger.info("Payment processed, PaymentId="+payment.getId());
		} catch (GoCardlessApiException e) {
			paymentTransactionInfoPlugin = new GoCardlessPaymentTransactionInfoPlugin(kbPaymentId, kbTransactionId,
					TransactionType.PURCHASE, amount, currency, PaymentPluginStatus.ERROR, e.getErrorMessage(),
					String.valueOf(e.getCode()), null, null, new DateTime(), null, null);
			logger.warn("Error occured in purchasePayment", e.getType(), e);
		}
	} else {
		logger.warn("Unable to fetch mandate, so cannot process payment");
		paymentTransactionInfoPlugin = new GoCardlessPaymentTransactionInfoPlugin(kbPaymentId, kbTransactionId,
				TransactionType.PURCHASE, amount, currency, PaymentPluginStatus.CANCELED, null,
				null, null, null, new DateTime(), null, null);
	}
	return paymentTransactionInfoPlugin;
}

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	public List<PaymentTransactionInfoPlugin> getPaymentInfo(UUID kbAccountId, UUID kbPaymentId,
			Iterable<PluginProperty> properties, TenantContext context) throws PaymentPluginApiException {

		List<PaymentTransactionInfoPlugin> paymentTransactionInfoPluginList = new ArrayList<>();
		String mandateId = getMandateId(kbAccountId, context) ;
		Mandate mandate = client.mandates().get(mandateId).execute(); //get GoCardless Mandate object
		String customerId = mandate.getLinks().getCustomer(); //retrieve customer ID from mandate

		Iterable<Payment> payments = client.payments().all().withCustomer(customerId).execute(); //get all payments related to customer

		for (Payment payment : payments) {
			String kbPaymentIdFromPayment = payment.getMetadata().get("kbPaymentId"); //get kbPaymentId from metadata in payment
			if(kbPaymentIdFromPayment != null && kbPaymentId.toString().equals(kbPaymentIdFromPayment)) {
				Currency killBillCurrency = convertGoCardlessCurrencyToKillBillCurrency(payment.getCurrency());
				PaymentPluginStatus status = convertGoCardlessToKillBillStatus(payment.getStatus());
				String kbTransactionPaymentIdStr = payment.getMetadata().get("kbTransactionId");
				UUID kbTransactionPaymentId = kbTransactionPaymentIdStr !=null?UUID.fromString(kbTransactionPaymentIdStr):null;
				List<PluginProperty> outputProperties = new ArrayList<PluginProperty>();
				outputProperties.add(new PluginProperty("mandateId",mandateId,false)); //arbitrary data to be returned to the caller
				outputProperties.add(new PluginProperty("customerId",customerId,false));  //arbitrary data to be returned to the caller
				outputProperties.add(new PluginProperty("gocardlessstatus",payment.getStatus(),false)); //arbitrary data to be returned to the caller
				GoCardlessPaymentTransactionInfoPlugin paymentTransactionInfoPlugin = new GoCardlessPaymentTransactionInfoPlugin(
						kbPaymentId, kbTransactionPaymentId, TransactionType.PURCHASE, new BigDecimal(payment.getAmount()), killBillCurrency,
						status, null, null, String.valueOf(payment.getId()), null, new DateTime(),
						new DateTime(payment.getCreatedAt()), outputProperties);
				logger.info("Created paymentTransactionInfoPlugin {}",paymentTransactionInfoPlugin);
				paymentTransactionInfoPluginList.add(paymentTransactionInfoPlugin);
			}
		}

		return paymentTransactionInfoPluginList;
	}

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@Singleton
// Handle /plugins/killbill-gocardless/checkout
@Path("/checkout")
public class GoCardlessCheckoutServlet {
    private final OSGIKillbillClock clock;
    private final GoCardlessPaymentPluginApi goCardlessPaymentPluginApi;
    private static final Logger logger = LoggerFactory.getLogger(GoCardlessCheckoutServlet.class);
    @Inject
    public GoCardlessCheckoutServlet(final OSGIKillbillClock clock,
                                     final GoCardlessPaymentPluginApi goCardlessPaymentPluginApi) {
        this.clock = clock;
        this.goCardlessPaymentPluginApi = goCardlessPaymentPluginApi;
    }
    // Setting up Direct Debit mandates using Hosted Payment Pages, before a payment method has been added to the account
    @POST
    public Result createSession(@Named("kbAccountId") final UUID kbAccountId,
                                @Named("success_redirect_url") final Optional<String> successUrl,
                                @Named("redirect_flow_description") final Optional<String> description,
                                @Named("lineItemName") final Optional<String> token,
                                @Local @Named("killbill_tenant") final Tenant tenant) throws PaymentPluginApiException {
    	logger.info("Inside createSession");
        final CallContext context = new PluginCallContext(GoCardlessActivator.PLUGIN_NAME, clock.getClock().getUTCNow(), kbAccountId, tenant.getId());
        final List<PluginProperty> properties = List.of(
                new PluginProperty("success_redirect_url", successUrl.orElse("https://developer.gocardless.com/example-redirect-uri/"), false),
                new PluginProperty("redirect_flow_description", description.orElse("Kill Bill payment"), false),
                new PluginProperty("session_token", token.orElse("killbill_token"), false));
        final HostedPaymentPageFormDescriptor hostedPaymentPageFormDescriptor = goCardlessPaymentPluginApi.buildFormDescriptor(kbAccountId,
                List.of(),
                properties,
                context);
        return Results.with(hostedPaymentPageFormDescriptor, Status.CREATED)
                .type(MediaType.json);
    }
}

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public class GoCardlessActivator extends KillbillActivatorBase{
//This is the plugin name and is used by Kill Bill to route payment to the appropriate payment plugin
	public static final String PLUGIN_NAME = "killbill-gocardless";
	@Override
    public void start(final BundleContext context) throws Exception {
        super.start(context);
        final GoCardlessPaymentPluginApi pluginApi = new GoCardlessPaymentPluginApi(killbillAPI,clock.getClock());
        registerPaymentPluginApi(context, pluginApi);
        // Register the servlet, which is used as the entry point to generate the Hosted Payment Pages redirect url
        final PluginApp pluginApp = new PluginAppBuilder(PLUGIN_NAME, killbillAPI, dataSource, super.clock, configProperties)
                .withRouteClass(GoCardlessCheckoutServlet.class)
                .withService(pluginApi)
                .withService(clock)
                .build();
        final HttpServlet goCardlessServlet = PluginApp.createServlet(pluginApp);
        registerServlet(context, goCardlessServlet);
    }
    private void registerPaymentPluginApi(final BundleContext context, final PaymentPluginApi api) {
        final Hashtable<String, String> props = new Hashtable<String, String>();
        props.put(OSGIPluginProperties.PLUGIN_NAME_PROP, PLUGIN_NAME);
        registrar.registerService(context, PaymentPluginApi.class, api, props);
    }
    private void registerServlet(final BundleContext context, final HttpServlet servlet) {
        final Hashtable<String, String> props = new Hashtable<String, String>();
        props.put(OSGIPluginProperties.PLUGIN_NAME_PROP, PLUGIN_NAME);
        registrar.registerService(context, Servlet.class, servlet, props);
    }
}