Java 11 migration: patterns starting with a (#1084)

* Moves abstract-factory pattern to java 11

* Moves abstract-document pattern to java 11

* Moves acyclic-visitor pattern to java 11

* Moves adapter pattern to java 11

* Moves aggregator-microservices pattern to java 11

* Moves api-gateway pattern to java 11

aggregator-microservices/aggregator-service/src/main/java/com/iluwatar/aggregator/microservices/Aggregator.java

@@ -23,6 +23,8 @@
 
 package com.iluwatar.aggregator.microservices;
 
+import static java.util.Objects.requireNonNullElse;
+
 import javax.annotation.Resource;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RequestMethod;
@@ -52,20 +54,14 @@ public class Aggregator {
   public Product getProduct() {
 
     var product = new Product();
-    String productTitle = informationClient.getProductTitle();
-    Integer productInventory = inventoryClient.getProductInventories();
+    var productTitle = informationClient.getProductTitle();
+    var productInventory = inventoryClient.getProductInventories();
 
-    if (productTitle != null) {
-      product.setTitle(productTitle);
-    } else {
-      product.setTitle("Error: Fetching Product Title Failed"); //Fallback to error message
-    }
+    //Fallback to error message
+    product.setTitle(requireNonNullElse(productTitle, "Error: Fetching Product Title Failed"));
 
-    if (productInventory != null) {
-      product.setProductInventories(productInventory);
-    } else {
-      product.setProductInventories(-1); //Fallback to default error inventory
-    }
+    //Fallback to default error inventory
+    product.setProductInventories(requireNonNullElse(productInventory, -1));
 
     return product;
   }

aggregator-microservices/aggregator-service/src/main/java/com/iluwatar/aggregator/microservices/ProductInformationClientImpl.java

@@ -42,19 +42,19 @@ public class ProductInformationClientImpl implements ProductInformationClient {
 
   @Override
   public String getProductTitle() {
-    String response = null;
-    var request =
-        HttpRequest.newBuilder().GET().uri(URI.create("http://localhost:51515/information"))
-            .build();
+    var request = HttpRequest.newBuilder()
+        .GET()
+        .uri(URI.create("http://localhost:51515/information"))
+        .build();
     var client = HttpClient.newHttpClient();
     try {
       var httpResponse = client.send(request, HttpResponse.BodyHandlers.ofString());
-      response = httpResponse.body();
+      return httpResponse.body();
     } catch (IOException ioe) {
       LOGGER.error("IOException Occurred", ioe);
     } catch (InterruptedException ie) {
       LOGGER.error("InterruptedException Occurred", ie);
     }
-    return response;
+    return null;
   }
 }

aggregator-microservices/aggregator-service/src/main/java/com/iluwatar/aggregator/microservices/ProductInventoryClientImpl.java

@@ -44,9 +44,10 @@ public class ProductInventoryClientImpl implements ProductInventoryClient {
   public Integer getProductInventories() {
     var response = "";
 
-    var request =
-        HttpRequest.newBuilder().GET().uri(URI.create("http://localhost:51516/inventories"))
-            .build();
+    var request = HttpRequest.newBuilder()
+        .GET()
+        .uri(URI.create("http://localhost:51516/inventories"))
+        .build();
     var client = HttpClient.newHttpClient();
     try {
       var httpResponse = client.send(request, HttpResponse.BodyHandlers.ofString());

aggregator-microservices/aggregator-service/src/test/java/com/iluwatar/aggregator/microservices/AggregatorTest.java

@@ -56,13 +56,13 @@ public class AggregatorTest {
    */
   @Test
   public void testGetProduct() {
-    String title = "The Product Title.";
-    int inventories = 5;
+    var title = "The Product Title.";
+    var inventories = 5;
 
     when(informationClient.getProductTitle()).thenReturn(title);
     when(inventoryClient.getProductInventories()).thenReturn(inventories);
 
-    Product testProduct = aggregator.getProduct();
+    var testProduct = aggregator.getProduct();
 
     assertEquals(title, testProduct.getTitle());
     assertEquals(inventories, testProduct.getProductInventories());

aggregator-microservices/information-microservice/src/test/java/com/iluwatar/information/microservice/InformationControllerTest.java

@@ -34,10 +34,8 @@ public class InformationControllerTest {
 
   @Test
   public void shouldGetProductTitle() {
-    InformationController infoController = new InformationController();
-
-    String title = infoController.getProductTitle();
-
+    var infoController = new InformationController();
+    var title = infoController.getProductTitle();
     assertEquals("The Product Title.", title);
   }
 

aggregator-microservices/inventory-microservice/src/test/java/com/iluwatar/inventory/microservice/InventoryControllerTest.java

@@ -33,10 +33,8 @@ import org.junit.jupiter.api.Test;
 public class InventoryControllerTest {
   @Test
   public void testGetProductInventories() {
-    InventoryController inventoryController = new InventoryController();
-
-    int numberOfInventories = inventoryController.getProductInventories();
-
+    var inventoryController = new InventoryController();
+    var numberOfInventories = inventoryController.getProductInventories();
     assertEquals(5, numberOfInventories);
   }
 }