Add API endpoint to get single product

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

@@ -39,9 +39,9 @@ public class UIBackendService {
 
     @Autowired
     public UIBackendService(CartService cartService,
-                            InventoryService inventoryService,
-                            OrderService orderService,
-                            @Value("${t2.computation-simulator.enabled}") boolean enableComputeIntensiveSimulation) {
+            InventoryService inventoryService,
+            OrderService orderService,
+            @Value("${t2.computation-simulator.enabled}") boolean enableComputeIntensiveSimulation) {
         this.cartService = cartService;
         this.inventoryService = inventoryService;
         this.orderService = orderService;
@@ -74,16 +74,27 @@ public List<Product> getAllProducts() {
         return inventoryService.getAllProducts();
     }
 
+    /**
+     * Gets a product by its ID.
+     *
+     * @return product
+     */
+    public Optional<Product> getProduct(String productId) {
+        return inventoryService.getSingleProduct(productId);
+    }
+
     /**
      * Add the given number units of product to a users cart.
      * <p>
-     * If the product is already in the cart, the units of that product will be updated.
+     * If the product is already in the cart, the units of that product will be
+     * updated.
      *
      * @param sessionId identifies the cart to add to
      * @param productId id of product to be added
      * @param units     number of units to be added (must not be negative)
      * @return successfully added item
-     * @throws ReservationFailedException if there is an error making reservations for the product
+     * @throws ReservationFailedException if there is an error making reservations
+     *                                    for the product
      */
     public Product addItemToCart(String sessionId, String productId, int units) throws ReservationFailedException {
         // contact inventory first, cause i'd rather have a dangling reservation than a
@@ -94,8 +105,8 @@ public Product addItemToCart(String sessionId, String productId, int units) thro
             addedProduct.setUnits(units);
         } catch (InsufficientUnitsAvailableException e) {
             throw new ReservationFailedException(String.format(
-                "Adding item %s with %s units to cart of session %s failed. Reason: %s",
-                productId, units, sessionId, e.getMessage()));
+                    "Adding item %s with %s units to cart of session %s failed. Reason: %s",
+                    productId, units, sessionId, e.getMessage()));
         }
         cartService.addItemToCart(sessionId, productId, units);
         return addedProduct;
@@ -104,7 +115,8 @@ public Product addItemToCart(String sessionId, String productId, int units) thro
     /**
      * Delete the given number units of product from a users cart.
      * <p>
-     * If the number of units in the cart decrease to zero or less, the product is remove from the cart. If the no such
+     * If the number of units in the cart decrease to zero or less, the product is
+     * remove from the cart. If the no such
      * product is in cart, do nothing.
      *
      * @param sessionId identifies the cart to delete from
@@ -149,16 +161,19 @@ public List<Product> getProductsInCart(String sessionId) {
     }
 
     /**
-     * Posts a request to start a transaction to the orchestrator. Attempts to delete the cart of the given sessionId
-     * once the orchestrator accepted the request. Nothing happens if the deletion of a cart fails, as the cart service
+     * Posts a request to start a transaction to the orchestrator. Attempts to
+     * delete the cart of the given sessionId
+     * once the orchestrator accepted the request. Nothing happens if the deletion
+     * of a cart fails, as the cart service
      * supposed to periodically remove out dated cart entries anyway.
      *
      * @param sessionId  identifies the session
      * @param cardNumber part of payment details
      * @param cardOwner  part of payment details
      * @param checksum   part of payment details
      */
-    public void confirmOrder(String sessionId, String cardNumber, String cardOwner, String checksum) throws OrderNotPlacedException {
+    public void confirmOrder(String sessionId, String cardNumber, String cardOwner, String checksum)
+            throws OrderNotPlacedException {
         try {
             orderService.confirmOrder(sessionId, cardNumber, cardOwner, checksum);
         } catch (Exception e) {
@@ -178,6 +193,7 @@ private void simulateComputeIntensiveTask(String sessionId) {
         LOG.info("Start simulation of an intensive computation task ... Session: {}", sessionId);
         // Returns the duration in milliseconds that the calculation took
         Double duration = computationSimulatorService.doCompute();
-        LOG.info("Finished simulation of an intensive computation task. Duration: {} ms, Session: {}", duration, sessionId);
+        LOG.info("Finished simulation of an intensive computation task. Duration: {} ms, Session: {}", duration,
+                sessionId);
     }
 }

src/main/java/de/unistuttgart/t2/modulith/uibackend/web/UIBackendController.java

@@ -5,8 +5,10 @@
 import de.unistuttgart.t2.modulith.uibackend.exceptions.OrderNotPlacedException;
 import de.unistuttgart.t2.modulith.uibackend.exceptions.ReservationFailedException;
 import io.swagger.v3.oas.annotations.Operation;
+import io.swagger.v3.oas.annotations.media.ArraySchema;
 import io.swagger.v3.oas.annotations.media.Content;
 import io.swagger.v3.oas.annotations.media.ExampleObject;
+import io.swagger.v3.oas.annotations.media.Schema;
 import io.swagger.v3.oas.annotations.responses.ApiResponse;
 import io.swagger.v3.oas.annotations.responses.ApiResponses;
 import org.slf4j.Logger;
@@ -15,14 +17,16 @@
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.*;
+import org.springframework.web.server.ResponseStatusException;
 
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
 
 /**
  * Defines the http endpoints of the UIBackend.
- * These endpoints are not used by the UI, but can be used e.g. for load testing the application.
+ * These endpoints are not used by the UI, but can be used e.g. for load testing
+ * the application.
  *
  * @author maumau
  * @author davidkopp
@@ -39,33 +43,61 @@ public UIBackendController(@Autowired UIBackendService service) {
     }
 
     /**
-     * @return a list of all products in the inventory
+     * Get all existing products in the inventory
+     * 
+     * @return list of products
      */
-    @Operation(summary = "List all available products")
+    @Operation(summary = "List all available products", description = "Retrieve a list of all available products.")
+    @ApiResponses(value = {
+            @ApiResponse(responseCode = "200", description = "List of products retrieved successfully", content = @Content(array = @ArraySchema(schema = @Schema(implementation = Product.class)))),
+    })
     @GetMapping("/products")
     public List<Product> getAllProducts() {
         return service.getAllProducts();
     }
 
+    /**
+     * Get a specific product by its ID
+     * 
+     * @param productId ID of the product
+     * @return product if ID exists
+     */
+    @Operation(summary = "Get product by ID", description = "Retrieve a product by its unique identifier.")
+    @ApiResponses(value = {
+            @ApiResponse(responseCode = "200", description = "Product retrieved successfully", content = @Content(schema = @Schema(implementation = Product.class))),
+            @ApiResponse(responseCode = "404", description = "Product not found", content = @Content(schema = @Schema(example = "{\"message\": \"Product with ID '123' not found\"}")))
+    })
+    @GetMapping("/products/{productId}")
+    public Product getProduct(@PathVariable String productId) {
+        return service.getProduct(productId)
+                .orElseThrow(() -> new ResponseStatusException(
+                        HttpStatus.NOT_FOUND, "Product with ID '" + productId + "' not found"));
+    }
+
     /**
      * Update units of the given products to the cart.
      * <p>
-     * Add something to the cart, if the number of units is positive or delete from the cart when it is negative. Only
-     * add the products to the cart if the requested number of unit is available. To achieve this, at first a
-     * reservations are placed in the inventory and only after the reservations are succeeded be are the products added
+     * Add something to the cart, if the number of units is positive or delete from
+     * the cart when it is negative. Only
+     * add the products to the cart if the requested number of unit is available. To
+     * achieve this, at first a
+     * reservations are placed in the inventory and only after the reservations are
+     * succeeded be are the products added
      * to the cart.
      *
      * @param sessionId         sessionId to identify the user's cart
-     * @param updateCartRequest request that contains the id of the products to be updated and the number of units to be
+     * @param updateCartRequest request that contains the id of the products to be
+     *                          updated and the number of units to be
      *                          added or deleted
      * @return list of successfully added items
      */
     @Operation(summary = "Update items in cart")
     @io.swagger.v3.oas.annotations.parameters.RequestBody(content = @Content(examples = @ExampleObject(value = "{\n\"content\": {\n    \"product-id\": 3\n  }\n}")))
-    @ApiResponses(value = {@ApiResponse(responseCode = "200", description = "Cart updated"),
-        @ApiResponse(responseCode = "500", description = "Cart could not be updated")})
+    @ApiResponses(value = { @ApiResponse(responseCode = "200", description = "Cart updated"),
+            @ApiResponse(responseCode = "500", description = "Cart could not be updated") })
     @PostMapping("/cart/{sessionId}")
-    public List<Product> updateCart(@PathVariable String sessionId, @RequestBody UpdateCartRequest updateCartRequest) throws ReservationFailedException {
+    public List<Product> updateCart(@PathVariable String sessionId, @RequestBody UpdateCartRequest updateCartRequest)
+            throws ReservationFailedException {
         List<Product> successfullyAddedProducts = new ArrayList<>();
 
         for (Map.Entry<String, Integer> product : updateCartRequest.getContent().entrySet()) {
@@ -96,29 +128,31 @@ public List<Product> getCart(@PathVariable String sessionId) {
 
     /**
      * Place an order, i.e. start a transaction.<br>
-     * Upon successfully placing the order, the cart is cleared and the session gets invalidated.<br>
+     * Upon successfully placing the order, the cart is cleared and the session gets
+     * invalidated.<br>
      * If the user wants to place another order he needs a new http session.
      *
      * @param request request to place an Order
      * @throws OrderNotPlacedException if the order could not be placed.
      */
     @Operation(summary = "Order all items in the cart", description = "Order all items in the cart")
-    @ApiResponses(value = {@ApiResponse(responseCode = "200", description = "Order for items is placed"),
-        @ApiResponse(responseCode = "500", description = "Order could not be placed")})
+    @ApiResponses(value = { @ApiResponse(responseCode = "200", description = "Order for items is placed"),
+            @ApiResponse(responseCode = "500", description = "Order could not be placed") })
     @PostMapping("/confirm")
     public void confirmOrder(@RequestBody OrderRequest request)
-        throws OrderNotPlacedException {
+            throws OrderNotPlacedException {
         service.confirmOrder(request.getSessionId(), request.getCardNumber(), request.getCardOwner(),
-            request.getChecksum());
+                request.getChecksum());
     }
 
     /**
-     * Creates the response entity if a request could not be served because a custom exception was thrown.
+     * Creates the response entity if a request could not be served because a custom
+     * exception was thrown.
      *
      * @param exception the exception that was thrown
      * @return a response entity with an exceptional message
      */
-    @ExceptionHandler({OrderNotPlacedException.class, ReservationFailedException.class})
+    @ExceptionHandler({ OrderNotPlacedException.class, ReservationFailedException.class })
     @ResponseStatus(HttpStatus.INTERNAL_SERVER_ERROR)
     public ResponseEntity<String> handleCustomException(Exception exception) {
         LOG.error("Internal server error. Caused by: {}", exception.getMessage());

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

@@ -16,13 +16,18 @@
 import org.mockito.Captor;
 import org.mockito.Mock;
 import org.mockito.junit.jupiter.MockitoExtension;
+import org.springframework.http.HttpStatus;
 import org.springframework.test.context.ActiveProfiles;
+import org.springframework.web.server.ResponseStatusException;
 
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 
 import static de.unistuttgart.t2.modulith.TestData.*;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.mockito.ArgumentMatchers.anyInt;
 import static org.mockito.ArgumentMatchers.anyString;
 import static org.mockito.Mockito.*;
 
@@ -54,6 +59,36 @@ public void setUp() {
         controller = new UIBackendController(service);
     }
 
+    @Test
+    public void getAllProducts() {
+        when(service.getAllProducts()).thenReturn(inventoryResponseAllProducts());
+
+        List<Product> products = controller.getAllProducts();
+
+        verify(service, times(1)).getAllProducts();
+        assertEquals(2, products.size());
+    }
+
+    @Test
+    public void getProduct() {
+        when(service.getProduct(productId)).thenReturn(inventoryResponse());
+
+        Product product = controller.getProduct(productId);
+
+        verify(service, times(1)).getProduct(productId);
+        assertEquals(productId, product.getId());
+    }
+
+    @Test
+    public void getProductNotFoundThrowsException() {
+        when(service.getProduct(productId)).thenReturn(Optional.empty());
+
+        ResponseStatusException exception = assertThrows(ResponseStatusException.class,
+                () -> controller.getProduct(productId));
+
+        assertEquals(HttpStatus.NOT_FOUND, exception.getStatusCode());
+    }
+
     @Test
     public void dontChangeCartIfUnitsAreZero() throws ReservationFailedException {
 
@@ -72,7 +107,8 @@ public void addItemToCart() throws ReservationFailedException {
         UpdateCartRequest request = new UpdateCartRequest(Map.of(productId, units));
         controller.updateCart(sessionId, request);
 
-        verify(service, times(1)).addItemToCart(sessionIdCaptor.capture(), productIdCaptor.capture(), unitsCaptor.capture());
+        verify(service, times(1)).addItemToCart(sessionIdCaptor.capture(), productIdCaptor.capture(),
+                unitsCaptor.capture());
         assertEquals(sessionId, sessionIdCaptor.getValue());
         assertEquals(productId, productIdCaptor.getValue());
         assertEquals(units, unitsCaptor.getValue());
@@ -95,7 +131,8 @@ public void removeItemFromCart() throws ReservationFailedException {
         UpdateCartRequest request = new UpdateCartRequest(Map.of(productId, -units));
         List<Product> addedProducts = controller.updateCart(sessionId, request);
 
-        verify(service, times(1)).deleteItemFromCart(sessionIdCaptor.capture(), productIdCaptor.capture(), unitsCaptor.capture());
+        verify(service, times(1)).deleteItemFromCart(sessionIdCaptor.capture(), productIdCaptor.capture(),
+                unitsCaptor.capture());
         assertEquals(sessionId, sessionIdCaptor.getValue());
         assertEquals(productId, productIdCaptor.getValue());
         assertEquals(units, unitsCaptor.getValue());
@@ -117,11 +154,11 @@ public final void updateCartRequestSerializingAndDeserializing() throws JsonProc
         ObjectMapper mapper = new ObjectMapper();
 
         UpdateCartRequest original = new UpdateCartRequest(
-            Map.of("c1e359ff-4cd7-4ede-93fb-378aced160e5", 1));
+                Map.of("c1e359ff-4cd7-4ede-93fb-378aced160e5", 1));
         String serialized = mapper.writeValueAsString(original);
         UpdateCartRequest deserialized = mapper.reader()
-            .forType(UpdateCartRequest.class)
-            .readValue(serialized);
+                .forType(UpdateCartRequest.class)
+                .readValue(serialized);
 
         assertEquals(original.getContent(), deserialized.getContent());
     }

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

@@ -16,9 +16,11 @@
 import org.springframework.test.context.ActiveProfiles;
 
 import java.util.List;
+import java.util.Optional;
 
 import static de.unistuttgart.t2.modulith.TestData.*;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.mockito.ArgumentMatchers.anyString;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
@@ -85,6 +87,19 @@ public void getAllProducts() {
         assertEquals(2, result.size());
     }
 
+    @Test
+    public void getSingleProduct() {
+
+        // setup
+        when(inventoryService.getSingleProduct(productId)).thenReturn(inventoryResponse());
+
+        // execute
+        Optional<Product> result = service.getProduct(productId);
+
+        // assert
+        assertTrue(result.isPresent());
+    }
+
     @Test
     public void addItemToCart() throws InsufficientUnitsAvailableException, ReservationFailedException {