Example of implementing the Saga pattern using a simple Java code

Category : Microservices | Sub Category : Microservices | By Prasad Bonam Last updated: 2023-07-15 15:03:30 Viewed : 354

Example of implementing the Saga pattern using a simple Java code:

Here is an example of implementing the Saga pattern using a simple Java code snippet:

javaCopy code
public class OrderSaga {
    private OrderService orderService;
    private PaymentService paymentService;
    private ShippingService shippingService;

    public OrderSaga(OrderService orderService, PaymentService paymentService, ShippingService shippingService) {
        this.orderService = orderService;
        this.paymentService = paymentService;
        this.shippingService = shippingService;
    }

    public void placeOrder(Order order) {
        try {
            // Step 1: Start the transaction
            orderService.createOrder(order);

            // Step 2: Make the payment
            paymentService.makePayment(order.getPaymentInfo());

            // Step 3: Ship the order
            shippingService.shipOrder(order.getId());

            // Step 4: Confirm the order
            orderService.confirmOrder(order.getId());
            
            // Saga completed successfully
            System.out.println("Order placed successfully.");
        } catch (Exception e) {
            // Handle exceptions and perform compensating actions if needed
            handleSagaFailure(order);
        }
    }

    private void handleSagaFailure(Order order) {
        try {
            // Step 5: Compensating action for shipping
            shippingService.cancelShipping(order.getId());

            // Step 6: Compensating action for payment
            paymentService.refundPayment(order.getPaymentInfo());

            // Step 7: Compensating action for order
            orderService.cancelOrder(order.getId());

            System.out.println("Saga execution failed. Order cancelled and compensating actions performed.");
        } catch (Exception e) {
            // Handle compensating action failures
            System.out.println("Compensating actions failed. Manual intervention required.");
        }
    }
}

In this example, we have an OrderSaga class that represents a saga for placing an order. It takes three services as dependencies: OrderService, PaymentService, and ShippingService. Each of these services is responsible for performing a specific step in the saga.

The placeOrder method executes the saga steps in sequence. If any step fails (i.e., an exception is thrown), the handleSagaFailure method is called to perform compensating actions and revert the changes made in the previous steps.

In this example, we assume the following methods are available in the respective services:

• OrderService: createOrder(order), confirmOrder(orderId), cancelOrder(orderId)
• PaymentService: makePayment(paymentInfo), refundPayment(paymentInfo)
• ShippingService: shipOrder(orderId), cancelShipping(orderId)

The handleSagaFailure method is responsible for executing the compensating actions in reverse order to undo the changes made by the previous steps. If any compensating action fails, appropriate error handling can be implemented to handle the failure.

Note that this example is simplified and does not cover all possible scenarios or error handling mechanisms. The actual implementation of the Saga pattern may vary depending on the specific requirements and frameworks used in your application.