Optimize get products from inventory database

src/main/java/de/unistuttgart/t2/modulith/inventory/InventoryService.java

@@ -6,9 +6,7 @@
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
-import java.util.List;
-import java.util.NoSuchElementException;
-import java.util.Optional;
+import java.util.*;
 
 /**
  * Manages the inventory and the reservations.
@@ -56,6 +54,20 @@ public Optional<Product> getSingleProduct(String productId) {
         return InventoryProductMapper.toProduct(inventoryItem);
     }
 
+    /**
+     * Get the products with the given productIds from the inventory.
+     * <p>
+     * If there are either no products with the given sessionId, or the retrieval of the products failed, an empty collection
+     * is returned.
+     *
+     * @param productIds collection of product ids to be retrieved
+     * @return products if product ids exists
+     */
+    public List<Product> getProducts(Collection<String> productIds) {
+        List<InventoryItem> inventoryItems = inventoryRepository.findAllById(productIds);
+        return inventoryItems.stream().map(InventoryProductMapper::toProduct).toList();
+    }
+
     /**
      * commit reservations associated with given sessionId.
      *

src/main/java/de/unistuttgart/t2/modulith/order/OrderService.java

@@ -15,8 +15,8 @@
 import org.springframework.data.mongodb.repository.config.EnableMongoRepositories;
 import org.springframework.stereotype.Service;
 
+import java.util.List;
 import java.util.NoSuchElementException;
-import java.util.Optional;
 
 /**
  * Creates and updates orders.
@@ -132,23 +132,18 @@ public String confirmOrder(String sessionId, String cardNumber, String cardOwner
     /**
      * Calculates the total of a users cart.
      * <p>
-     * Depends on the cart module to get the cart content and depends on the inventory module to get the price per
-     * unit.
+     * Depends on the cart module to get the cart content and
+     * depends on the inventory module to get the price for each product.
      *
      * @param sessionId identifies the session to get total for
      * @return the total money to pay for products in the cart
      */
     private double getTotal(String sessionId) {
         CartContent cart = cartService.getCart(sessionId).orElse(new CartContent());
-
         double total = 0;
-
-        for (String productId : cart.getProductIds()) {
-            Optional<Product> product = inventoryService.getSingleProduct(productId);
-            if (product.isEmpty()) {
-                return 0;
-            }
-            total += product.get().getPrice() * cart.getUnits(productId);
+        List<Product> products = inventoryService.getProducts(cart.getProductIds());
+        for (Product product : products) {
+            total += product.getPrice() * cart.getUnits(product.getId());
         }
         return total;
     }

src/main/java/de/unistuttgart/t2/modulith/uibackend/UIBackendService.java

@@ -138,11 +138,10 @@ public List<Product> getProductsInCart(String sessionId) {
         if (cart.isPresent()) {
             CartContent cartContent = cart.get();
 
-            for (String productId : cartContent.getProductIds()) {
-                inventoryService.getSingleProduct(productId).ifPresent(p -> {
-                    p.setUnits(cartContent.getUnits(productId));
-                    results.add(p);
-                });
+            List<Product> products = inventoryService.getProducts(cartContent.getProductIds());
+            for (Product product : products) {
+                product.setUnits(cartContent.getUnits(product.getId()));
+                results.add(product);
             }
         }
 

src/test/java/de/unistuttgart/t2/modulith/TestData.java

@@ -54,6 +54,11 @@ public static Optional<Product> inventoryResponse() {
         return Optional.of(new Product(productId, "name", "description", 5, price));
     }
 
+    public static List<Product> inventoryResponseOneProductInList() {
+        Product product1 = inventoryResponse().get();
+        return new ArrayList<>(List.of(product1));
+    }
+
     public static Optional<Product> anotherInventoryResponse() {
         return Optional.of(new Product(anotherProductId, "name2", "description2", 5, anotherPrice));
     }

src/test/java/de/unistuttgart/t2/modulith/inventory/InventoryServiceTests.java

@@ -74,6 +74,24 @@ public void getSingleProduct() {
         assertEquals(1.0, product.getPrice());
     }
 
+    @Test
+    public void getProducts() {
+        // setup inventory response
+        List<Product> allProducts = inventoryResponseAllProducts();
+        List<InventoryItem> inventoryItems = allProducts.stream().map(InventoryProductMapper::toInventoryItem).toList();
+        List<String> ids = inventoryItems.stream().map(InventoryItem::getId).toList();
+        when(productRepository.findAllById(ids)).thenReturn(inventoryItems);
+
+        // execute
+        List<Product> products = inventoryService.getProducts(ids);
+
+        // assert
+        assertNotNull(products);
+        assertEquals(2, products.size());
+        assertEquals(productId, products.get(0).getId());
+        assertEquals(anotherProductId, products.get(1).getId());
+    }
+
     @Test
     public void makeReservation() throws InsufficientUnitsAvailableException {
         // setup inventory response

src/test/java/de/unistuttgart/t2/modulith/order/OrderConfirmIntegrationTests.java

@@ -3,8 +3,8 @@
 import de.unistuttgart.t2.modulith.cart.CartService;
 import de.unistuttgart.t2.modulith.cart.repository.CartItem;
 import de.unistuttgart.t2.modulith.cart.repository.CartRepository;
-import de.unistuttgart.t2.modulith.inventory.InventoryService;
 import de.unistuttgart.t2.modulith.inventory.InsufficientUnitsAvailableException;
+import de.unistuttgart.t2.modulith.inventory.InventoryService;
 import de.unistuttgart.t2.modulith.inventory.repository.InventoryItem;
 import de.unistuttgart.t2.modulith.inventory.repository.InventoryRepository;
 import de.unistuttgart.t2.modulith.inventory.repository.ReservationRepository;
@@ -114,7 +114,7 @@ public void confirmOrder_CalledMultipleTimes_ErrorIsThrown() throws Exception {
     public void confirmOrder_CalculatingTotalFails_OrderIsNotPlaced() throws PaymentFailedException {
 
         // setup
-        when(inventoryService.getSingleProduct(productId)).thenThrow(new RuntimeException("runtime error"));
+        when(inventoryService.getProducts(anyCollection())).thenThrow(new RuntimeException("runtime error"));
 
         // execute
         Exception actualException = assertThrows(Exception.class,

src/test/java/de/unistuttgart/t2/modulith/order/OrderDBTests.java

@@ -84,7 +84,8 @@ public void confirmOrder() throws Exception {
 
         // Setup mocks
         when(cartService.getCart(sessionId)).thenReturn(cartResponse());
-        when(inventoryService.getSingleProduct(productId)).thenReturn(inventoryResponse());
+        when(inventoryService.getProducts(cartResponse().get().getProductIds()))
+            .thenReturn(inventoryResponseOneProductInList());
 
         // execute
         String id = orderService.confirmOrder(sessionId, "cardNumber", "cardOwner", "checksum");

src/test/java/de/unistuttgart/t2/modulith/order/OrderServiceTests.java

@@ -42,7 +42,7 @@ public void beforeEach() {
     public void confirmOrderSucceeds() throws Exception {
 
         when(cartService.getCart(sessionId)).thenReturn(cartResponse());
-        when(inventoryService.getSingleProduct(productId)).thenReturn(inventoryResponse());
+        when(inventoryService.getProducts(anyCollection())).thenReturn(inventoryResponseOneProductInList());
         when(orderRepository.save(any())).thenReturn(new OrderItem(sessionId));
 
         orderService.confirmOrder(sessionId, "cardNumber", "cardOwner", "checksum");

src/test/java/de/unistuttgart/t2/modulith/uibackend/UIBackendServiceTests.java

@@ -127,7 +127,8 @@ public void deleteItemFromCart() {
     public void getProductsInCart() {
         // setup
         when(cartService.getCart(sessionId)).thenReturn(cartResponse());
-        when(inventoryService.getSingleProduct(productId)).thenReturn(inventoryResponse());
+        when(inventoryService.getProducts(cartResponse().get().getProductIds()))
+            .thenReturn(inventoryResponseOneProductInList());
 
         // execute
         List<Product> result = service.getProductsInCart(sessionId);