SOPE Project Phase 2 completed - state design pattern

Author: Astrogeek77

Projects/SOPE/src/main/java/com/gautam/SOPE/orderengine/controller/OrderController.java

@@ -1,5 +1,6 @@
 package com.gautam.SOPE.orderengine.controller;
 
+import com.gautam.SOPE.orderengine.model.Order;
 import com.gautam.SOPE.orderengine.service.PaymentService;
 import org.springframework.web.bind.annotation.*;
 
@@ -18,6 +19,21 @@ public OrderController(PaymentService paymentService) {
     @PostMapping("/checkout")
     public String checkout(@RequestParam String type, @RequestParam BigDecimal amount) {
         paymentService.checkout(type, amount);
+
+        // Simulation
+        Order order = new Order();
+        order.printStatus(); // Output: Order is currently in [NEW] state...
+
+        order.nextState();   // Output: Order payment processed...
+        order.printStatus(); // Output: Order is currently in [PAID] state...
+
+        order.nextState();   // Output: Order has been shipped!
+        order.printStatus(); // Output: Order is currently in [SHIPPED] state.
+
+        order.nextState();   // Output: Order is already shipped...
+
         return "Payment processed via " + type;
     }
+
+
 }

Projects/SOPE/src/main/java/com/gautam/SOPE/orderengine/model/Order.java

@@ -0,0 +1,31 @@
+package com.gautam.SOPE.orderengine.model;
+
+import com.gautam.SOPE.orderengine.state.OrderState;
+import com.gautam.SOPE.orderengine.state.NewState;
+
+public class Order {
+
+    private OrderState state;
+
+    // Default constructor sets initial state
+    public Order() {
+        this.state = new NewState();
+    }
+
+    public void setState(OrderState state) {
+        this.state = state;
+    }
+
+    public OrderState getState() {
+        return state;
+    }
+
+    // The "Request" methods that delegate to the current state
+    public void nextState() {
+        state.next(this);
+    }
+
+    public void printStatus() {
+        state.printStatus();
+    }
+}

Projects/SOPE/src/main/java/com/gautam/SOPE/orderengine/state/NewState.java

@@ -0,0 +1,16 @@
+package com.gautam.SOPE.orderengine.state;
+
+import com.gautam.SOPE.orderengine.model.Order;
+
+public class NewState implements OrderState {
+    @Override
+    public void next(Order order) {
+        System.out.println("Order payment processed successfully.");
+        order.setState(new PaidState());
+    }
+
+    @Override
+    public void printStatus() {
+        System.out.println("Order is currently in [NEW] state. Waiting for payment.");
+    }
+}

Projects/SOPE/src/main/java/com/gautam/SOPE/orderengine/state/OrderState.java

@@ -0,0 +1,8 @@
+package com.gautam.SOPE.orderengine.state;
+
+import com.gautam.SOPE.orderengine.model.Order;
+
+public interface OrderState {
+    void next(Order order);
+    void printStatus();
+}

Projects/SOPE/src/main/java/com/gautam/SOPE/orderengine/state/PaidState.java

@@ -0,0 +1,16 @@
+package com.gautam.SOPE.orderengine.state;
+
+import com.gautam.SOPE.orderengine.model.Order;
+
+public class PaidState implements OrderState {
+    @Override
+    public void next(Order order) {
+        System.out.println("Order has been shipped!");
+        order.setState(new ShippedState());
+    }
+
+    @Override
+    public void printStatus() {
+        System.out.println("Order is currently in [PAID] state. Preparing for shipment.");
+    }
+}

Projects/SOPE/src/main/java/com/gautam/SOPE/orderengine/state/ShippedState.java

@@ -0,0 +1,15 @@
+package com.gautam.SOPE.orderengine.state;
+
+import com.gautam.SOPE.orderengine.model.Order;
+
+public class ShippedState implements OrderState {
+    @Override
+    public void next(Order order) {
+        System.out.println("Order is already shipped. No further steps.");
+    }
+
+    @Override
+    public void printStatus() {
+        System.out.println("Order is currently in [SHIPPED] state.");
+    }
+}

Projects/SOPE/src/main/java/com/gautam/SOPE/orderengine/util/OrderStateConverter.java

@@ -0,0 +1,25 @@
+package com.gautam.SOPE.orderengine.util;
+
+import com.gautam.SOPE.orderengine.state.*;
+import jakarta.persistence.AttributeConverter;
+import jakarta.persistence.Converter;
+
+@Converter(autoApply = true)
+public class OrderStateConverter implements AttributeConverter<OrderState, String> {
+
+    @Override
+    public String convertToDatabaseColumn(OrderState state) {
+        if (state instanceof NewState) return "NEW";
+        if (state instanceof PaidState) return "PAID";
+        if (state instanceof ShippedState) return "SHIPPED";
+        return "UNKNOWN";
+    }
+
+    @Override
+    public OrderState convertToEntityAttribute(String dbData) {
+        if ("NEW".equals(dbData)) return new NewState();
+        if ("PAID".equals(dbData)) return new PaidState();
+        if ("SHIPPED".equals(dbData)) return new ShippedState();
+        return new NewState(); // Default fallback
+    }
+}

Projects/SOPE/src/test/java/com/gautam/SOPE/orderengine/model/OrderStateTest.java

@@ -0,0 +1,45 @@
+package com.gautam.SOPE.orderengine.model;
+
+import com.gautam.SOPE.orderengine.state.NewState;
+import com.gautam.SOPE.orderengine.state.PaidState;
+import com.gautam.SOPE.orderengine.state.ShippedState;
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.*;
+
+class OrderStateTest {
+
+    @Test
+    void testOrderLifecycleFlow() {
+        // 1. Setup - Create the object
+        Order order = new Order();
+
+        // 2. Assert Initial State
+        // explicitly check the class type to verify the state
+        assertTrue(order.getState() instanceof NewState, "Order should start in NEW state");
+
+        // 3. Act - Transition to next state
+        order.nextState();
+
+        // 4. Assert - Verify transition to PAID
+        assertTrue(order.getState() instanceof PaidState, "Order should transition to PAID state after first next()");
+
+        // 5. Act - Transition to next state
+        order.nextState();
+
+        // 6. Assert - Verify transition to SHIPPED
+        assertTrue(order.getState() instanceof ShippedState, "Order should transition to SHIPPED state");
+    }
+
+    @Test
+    void testShippedStateIsFinal() {
+        // Setup an order manually in the SHIPPED state to save time
+        Order order = new Order();
+        order.setState(new ShippedState());
+
+        // Act - Try to move past the final state
+        order.nextState();
+
+        // Assert - Should still be SHIPPED (idempotency)
+        assertTrue(order.getState() instanceof ShippedState, "Order should remain in SHIPPED state");
+    }
+}