#297 Create Spring Boot-backed API Gateway that aggregates calls to the Image and Price microservices

api-gateway/pom.xml

@@ -9,11 +9,66 @@
   </parent>
   <modelVersion>4.0.0</modelVersion>
   <artifactId>api-gateway</artifactId>
+  <packaging>jar</packaging>
+
+  <properties>
+    <spring.version>4.2.5.RELEASE</spring.version>
+    <spring-boot.version>1.3.3.RELEASE</spring-boot.version>
+  </properties>
+
+  <dependencyManagement>
+    <dependencies>
+      <dependency>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-dependencies</artifactId>
+        <version>${spring-boot.version}</version>
+        <type>pom</type>
+        <scope>import</scope>
+      </dependency>
+    </dependencies>
+  </dependencyManagement>
   <dependencies>
+    <dependency>
+      <groupId>org.springframework</groupId>
+      <artifactId>spring-webmvc</artifactId>
+      <version>${spring.version}</version>
+    </dependency>
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-web</artifactId>
+      <version>${spring-boot.version}</version>
+    </dependency>
     <dependency>
       <groupId>junit</groupId>
       <artifactId>junit</artifactId>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>org.mockito</groupId>
+      <artifactId>mockito-core</artifactId>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.apache.httpcomponents</groupId>
+      <artifactId>httpclient</artifactId>
+      <version>4.5.2</version>
+    </dependency>
   </dependencies>
+
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-maven-plugin</artifactId>
+        <version>${spring-boot.version}</version>
+        <executions>
+          <execution>
+            <goals>
+              <goal>repackage</goal>
+            </goals>
+          </execution>
+        </executions>
+      </plugin>
+    </plugins>
+  </build>
 </project>

api-gateway/src/main/java/com/iluwatar/api/gateway/ApiGateway.java

@@ -1,21 +1,31 @@
 package com.iluwatar.api.gateway;
 
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import javax.annotation.Resource;
+
 /**
  * The ApiGateway aggregates calls to microservices based on the needs of the individual clients.
  */
+@RestController
 public class ApiGateway {
 
-  private ImageService imageService = new ImageService();
+  @Resource
-  private PriceService priceService = new PriceService();
+  private ImageClient imageClient;
+
+  @Resource
+  private PriceClient priceClient;
 
   /**
    * Retrieves product information that desktop clients need
    * @return Product information for clients on a desktop
    */
+  @RequestMapping("/desktop")
   public DesktopProduct getProductDesktop() {
     DesktopProduct desktopProduct = new DesktopProduct();
-    desktopProduct.setImagePath(imageService.getImagePath());
+    desktopProduct.setImagePath(imageClient.getImagePath());
-    desktopProduct.setPrice(priceService.getPrice());
+    desktopProduct.setPrice(priceClient.getPrice());
     return desktopProduct;
   }
 
@@ -23,9 +33,10 @@ public class ApiGateway {
    * Retrieves product information that mobile clients need
    * @return Product information for clients on a mobile device
    */
+  @RequestMapping("/mobile")
   public MobileProduct getProductMobile() {
     MobileProduct mobileProduct = new MobileProduct();
-    mobileProduct.setPrice(priceService.getPrice());
+    mobileProduct.setPrice(priceClient.getPrice());
     return mobileProduct;
   }
 }

api-gateway/src/main/java/com/iluwatar/api/gateway/App.java

@@ -1,5 +1,8 @@
 package com.iluwatar.api.gateway;
 
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
 /**
  * With the Microservices pattern, a client may need data from multiple different microservices.
  * If the client called each microservice directly, that could contribute to longer load times,
@@ -18,13 +21,15 @@ package com.iluwatar.api.gateway;
  *
  * <p>
  * This implementation shows what the API Gateway pattern could look like for an e-commerce site.
- * In this case, the (@link ImageService) and (@link PriceService) represent our microservices.
+ * The {@link ApiGateway} makes calls to the Image and Price microservices using the
- * Customers viewing the site on a desktop device can see both price information and an image of
+ * {@link ImageClientImpl} and {@link PriceClientImpl} respectively. Customers viewing the site on a
- * a product, so the (@link ApiGateway) calls both of the microservices and aggregates the data in
+ * desktop device can see both price information and an image of a product, so the {@link ApiGateway}
- * the (@link DesktopProduct) model. However, mobile users only see price information; they do not
+ * calls both of the microservices and aggregates the data in the {@link DesktopProduct} model.
- * see a product image. For mobile users, the (@link ApiGateway) only retrieves price information,
+ * However, mobile users only see price information; they do not see a product image. For mobile
- * which it uses to populate the (@link MobileProduct).
+ * users, the {@link ApiGateway} only retrieves price information, which it uses to populate the
+ * {@link MobileProduct}.
  */
+@SpringBootApplication
 public class App {
 
   /**
@@ -34,13 +39,6 @@ public class App {
    *          command line args
    */
   public static void main(String[] args) {
-    ApiGateway apiGateway = new ApiGateway();
+    SpringApplication.run(App.class, args);
-
-    DesktopProduct desktopProduct = apiGateway.getProductDesktop();
-    System.out.println(String.format("Desktop Product \nPrice: %s\nImage path: %s",
-        desktopProduct.getPrice(), desktopProduct.getImagePath()));
-
-    MobileProduct mobileProduct = apiGateway.getProductMobile();
-    System.out.println(String.format("Mobile Product \nPrice: %s", mobileProduct.getPrice()));
   }
 }

api-gateway/src/main/java/com/iluwatar/api/gateway/DesktopProduct.java

@@ -4,8 +4,14 @@ package com.iluwatar.api.gateway;
  * Encapsulates all of the information that a desktop client needs to display a product.
  */
 public class DesktopProduct {
-
+  /**
+   * The price of the product
+   */
   private String price;
+
+  /**
+   * The path to the image of the product
+   */
   private String imagePath;
 
   public String getPrice() {

api-gateway/src/main/java/com/iluwatar/api/gateway/ImageClient.java

@@ -0,0 +1,8 @@
+package com.iluwatar.api.gateway;
+
+/**
+ * An interface used to communicate with the Image microservice
+ */
+public interface ImageClient {
+  String getImagePath();
+}

api-gateway/src/main/java/com/iluwatar/api/gateway/ImageClientImpl.java

@@ -0,0 +1,34 @@
+package com.iluwatar.api.gateway;
+
+import org.apache.http.client.methods.CloseableHttpResponse;
+import org.apache.http.client.methods.HttpGet;
+import org.apache.http.impl.client.CloseableHttpClient;
+import org.apache.http.impl.client.HttpClients;
+import org.apache.http.util.EntityUtils;
+import org.springframework.stereotype.Component;
+
+import java.io.IOException;
+
+/**
+ * An adapter to communicate with the Image microservice
+ */
+@Component
+public class ImageClientImpl implements ImageClient{
+  /**
+   * Makes a simple HTTP Get request to the Image microservice
+   * @return The path to the image
+   */
+  @Override
+  public String getImagePath() {
+    String response = null;
+    try (CloseableHttpClient httpClient = HttpClients.createDefault()) {
+      HttpGet httpGet = new HttpGet("http://localhost:50005/image-path");
+      try (CloseableHttpResponse httpResponse = httpClient.execute(httpGet)) {
+        response = EntityUtils.toString(httpResponse.getEntity());
+      }
+    } catch (IOException e) {
+      e.printStackTrace();
+    }
+    return response;
+  }
+}

api-gateway/src/main/java/com/iluwatar/api/gateway/ImageService.java

@@ -1,15 +0,0 @@
-package com.iluwatar.api.gateway;
-
-/**
- * Represents a microservice used to retrieve image data.
- */
-public class ImageService {
-
-  /**
-   * Gets the image path
-   * @return the image path
-   */
-  public String getImagePath() {
-    return "/product-image.png";
-  }
-}

api-gateway/src/main/java/com/iluwatar/api/gateway/MobileProduct.java

@@ -4,7 +4,9 @@ package com.iluwatar.api.gateway;
  * Encapsulates all of the information that mobile client needs to display a product.
  */
 public class MobileProduct {
-
+  /**
+   * The price of the product
+   */
   private String price;
 
   public String getPrice() {

api-gateway/src/main/java/com/iluwatar/api/gateway/PriceClient.java

@@ -0,0 +1,8 @@
+package com.iluwatar.api.gateway;
+
+/**
+ * An interface used to communicate with the Price microservice
+ */
+public interface PriceClient {
+  String getPrice();
+}

api-gateway/src/main/java/com/iluwatar/api/gateway/PriceClientImpl.java

@@ -0,0 +1,34 @@
+package com.iluwatar.api.gateway;
+
+import org.apache.http.client.methods.CloseableHttpResponse;
+import org.apache.http.client.methods.HttpGet;
+import org.apache.http.impl.client.CloseableHttpClient;
+import org.apache.http.impl.client.HttpClients;
+import org.apache.http.util.EntityUtils;
+import org.springframework.stereotype.Component;
+
+import java.io.IOException;
+
+/**
+ * An adapter to communicate with the Price microservice
+ */
+@Component
+public class PriceClientImpl implements PriceClient{
+  /**
+   * Makes a simple HTTP Get request to the Price microservice
+   * @return The price of the product
+   */
+  @Override
+  public String getPrice() {
+    String response = null;
+    try (CloseableHttpClient httpClient = HttpClients.createDefault()) {
+      HttpGet httpGet = new HttpGet("http://localhost:50006/price");
+      try (CloseableHttpResponse httpResponse = httpClient.execute(httpGet)) {
+        response = EntityUtils.toString(httpResponse.getEntity());
+      }
+    } catch (IOException e) {
+      e.printStackTrace();
+    }
+    return response;
+  }
+}

api-gateway/src/main/java/com/iluwatar/api/gateway/PriceService.java

@@ -1,15 +0,0 @@
-package com.iluwatar.api.gateway;
-
-/**
- * Represents a microservice used to retrieve price data.
- */
-public class PriceService {
-
-  /**
-   * Gets the price
-   * @return the price
-   */
-  public String getPrice() {
-    return "20";
-  }
-}

api-gateway/src/main/resources/application.properties

@@ -0,0 +1 @@
+server.port=50004

api-gateway/src/test/java/com/iluwatar/api/gateway/ApiGatewayTest.java

@@ -1,21 +1,44 @@
 package com.iluwatar.api.gateway;
 
+import org.junit.Before;
 import org.junit.Test;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
 
 import static org.junit.Assert.assertEquals;
+import static org.mockito.Mockito.when;
 
 public class ApiGatewayTest {
 
+  @InjectMocks
+  private ApiGateway apiGateway;
+
+  @Mock
+  private ImageClient imageClient;
+
+  @Mock
+  private PriceClient priceClient;
+
+  @Before
+  public void setup() {
+    MockitoAnnotations.initMocks(this);
+  }
+
   /**
    * Tests getting the data for a desktop client
    */
   @Test
   public void testGetProductDesktop() {
-    ApiGateway apiGateway = new ApiGateway();
+    String imagePath = "/product-image.png";
+    String price = "20";
+    when(imageClient.getImagePath()).thenReturn(imagePath);
+    when(priceClient.getPrice()).thenReturn(price);
+
     DesktopProduct desktopProduct = apiGateway.getProductDesktop();
 
-    assertEquals("20", desktopProduct.getPrice());
+    assertEquals(price, desktopProduct.getPrice());
-    assertEquals("/product-image.png", desktopProduct.getImagePath());
+    assertEquals(imagePath, desktopProduct.getImagePath());
   }
 
   /**
@@ -23,9 +46,11 @@ public class ApiGatewayTest {
    */
   @Test
   public void testGetProductMobile() {
-    ApiGateway apiGateway = new ApiGateway();
+    String price = "20";
+    when(priceClient.getPrice()).thenReturn(price);
+
     MobileProduct mobileProduct = apiGateway.getProductMobile();
 
-    assertEquals("20", mobileProduct.getPrice());
+    assertEquals(price, mobileProduct.getPrice());
   }
 }

api-gateway/src/test/java/com/iluwatar/api/gateway/AppTest.java

@@ -1,17 +0,0 @@
-package com.iluwatar.api.gateway;
-
-import org.junit.Test;
-
-/**
- *
- * Application test
- *
- */
-public class AppTest {
-
-  @Test
-  public void test() throws Exception {
-    String[] args = {};
-    App.main(args);
-  }
-}